Dry Grinding - Carbonated Ultrasound-Assisted Water Leaching of Carbothermally Reduced Lithium-Ion Battery Black Mass Towards Enhanced Selective Extraction of Lithium and Recovery of High-Value Metals.pdf
The document presents a dry grinding and carbonated ultrasound-assisted water leaching (CUAWL) process for recycling spent lithium-ion battery black mass containing anode and cathode materials. The process aims to enhance selective lithium carbonate recovery and reduce energy requirements for crystallization while maximizing recovery of high-value metals like nickel, manganese, and cobalt. Key steps include carbothermic reduction roasting of the black mass, followed by dry grinding and CUAWL. Optimization studies examined factors affecting metal leaching efficiency. The optimized method achieved up to 92.25% selective lithium recovery for a mixture of multiple cathode materials.
This document discusses a study on extracting metals from spent lithium-ion batteries. It presents the methodology used, which involves discharging, dismantling, crushing, sieving and then leaching with acid to extract metals like lithium, cobalt, nickel, and manganese. The optimal leaching conditions were investigated, and results show that leaching efficiency of over 90% for lithium, 49% for cobalt, 94.6% for nickel and 48.6% for manganese can be achieved using 1M sulfuric acid at 368K for 240 minutes. The document also discusses industrial recycling processes and concludes that leaching is an essential step for effective metal recovery from spent lithium-ion batteries.
Recycling and Reusing of used lithium ion batteriesJisha Krishnan
The document outlines the recycling and reuse of lithium ion batteries. It discusses the motivation for recycling due to environmental pollution and resource exploitation. It describes the lithium cell structure and reaction, and details both hydrometallurgical and pyrometallurgical recycling processes. Used batteries can be reused in power banks or for rural solar lighting systems. The conclusion emphasizes the reduction of battery waste, proper recycling, resource savings, and increased job opportunities.
Single-atom catalysts for biomass-derived drop-in chemicalsPawan Kumar
Conversion of biomass to fuel and drop-in chemicals is envisaged to solve the problem of depleting fossil fuel reserves while leveling-off the staggering CO2 concentration. By-passing the natural carbon cycle via the transformation of abundant lignocellulosic biomass into chemicals does not add any extra CO2 to the environment and the net CO2 concentration remains the same. The paradigm shifts from fossil fuel-based chemicals to biomass-derived products will rely on efficient and cost-effective catalysts that can compete with cheap and readily available fossil fuels. Existing transition and noble metal-based nanoparticle catalysts either in the supported or unsupported form are crippling due to poor activity/selectivity, deactivation of catalytically active sites, and the complex composition, recalcitrant nature, and high moisture content of biomass. Single-atom catalysts (SACs) possessing single-atom centers decorated on support have shown great promise in biomass conversion due to their unique geometric configuration, electronic properties, and ensemble effect. In contrast to traditional catalytic systems, SACs encompass the advantages of both heterogeneous and homogeneous catalysts with improved performance and easy recyclability. Because of the availability of each metal center for the reaction and unique geometrical configuration, SACs have displayed exceptional catalytic activity and selectivity (~95% in most cases). In addition, the SACs show increased thermal and chemical stability due to the stabilization of the metal center on the support. The present chapter highlights the various aspects of SACs for efficient and selective biomass conversion into drop-in chemicals.
This document summarizes research on hydrogen production in Mexico. The main areas of research are: 1) Hydrogen production from biological processes and wastes, which accounts for 40.4% of published papers. 2) Hydrogen production through conventional and non-conventional fuels, along with CO2 capture and catalysis, which accounts for 22.4% of papers. 3) Hydrogen production through photocatalysis and photoelectrocatalysis, which accounts for 14.1% of papers. A wide variety of potential applications could follow from these contributions to strengthen hydrogen research and take advantage of opportunities in Mexico and worldwide.
This document summarizes research on hydrogen production in Mexico. The most active area of research is biological processes, representing 40% of published papers, focusing on topics like bioreactors. The next most active area is catalysis and modified hydrogen processes from conventional sources, representing 22% of papers. Research on photocatalysis and photoelectrocatalysis focuses on developing efficient, stable, and inexpensive photocatalytic materials. Theoretical studies concentrate on optimizing reactor design and evaluating efficiencies. Electrolysis research proposes novel alloys and electrocatalysts. The review aims to assess scientific activity and advances in hydrogen production in Mexico.
HYDROGEN GENERATION FROM WASTE WATER BY USING SOLAR ENERGY | J4RV3I11004Journal For Research
Objective of this paper is to produce hydrogen which is an ideal fuel for the next generation because it is abundantly available in nature, energy efficient and clean. Wide varieties of technologies are available to produce hydrogen but only few of them are considered environmental friendly. Solar water splitting via photo catalytic reaction is one of them which have attracted tremendous attention. In this paper we are working on hydrogen production via solar splitting. Photo catalytic water splitting is one of the promising technologies to produce pure and clean hydrogen. Since it is reasonable having low process cost and has a small reactor, it can be made for house hold application and hence has a huge market potential. Generation of hydrogen under visible irradiation is the main area of work. Based on the literature reported here, visible irradiation can be achieved by doping of TiO2 with metal or non-metal. We have used Fe doping to increase the efficiency. The result indicates that Fe doped sieves produce more hydrogen than the normal TiO2 coated sieve and the efficiency can be increased if we increase the number of doped sieves and surface area.
Nanostructured composite materials for CO2 activationPawan Kumar
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
This document discusses a study on extracting metals from spent lithium-ion batteries. It presents the methodology used, which involves discharging, dismantling, crushing, sieving and then leaching with acid to extract metals like lithium, cobalt, nickel, and manganese. The optimal leaching conditions were investigated, and results show that leaching efficiency of over 90% for lithium, 49% for cobalt, 94.6% for nickel and 48.6% for manganese can be achieved using 1M sulfuric acid at 368K for 240 minutes. The document also discusses industrial recycling processes and concludes that leaching is an essential step for effective metal recovery from spent lithium-ion batteries.
Recycling and Reusing of used lithium ion batteriesJisha Krishnan
The document outlines the recycling and reuse of lithium ion batteries. It discusses the motivation for recycling due to environmental pollution and resource exploitation. It describes the lithium cell structure and reaction, and details both hydrometallurgical and pyrometallurgical recycling processes. Used batteries can be reused in power banks or for rural solar lighting systems. The conclusion emphasizes the reduction of battery waste, proper recycling, resource savings, and increased job opportunities.
Single-atom catalysts for biomass-derived drop-in chemicalsPawan Kumar
Conversion of biomass to fuel and drop-in chemicals is envisaged to solve the problem of depleting fossil fuel reserves while leveling-off the staggering CO2 concentration. By-passing the natural carbon cycle via the transformation of abundant lignocellulosic biomass into chemicals does not add any extra CO2 to the environment and the net CO2 concentration remains the same. The paradigm shifts from fossil fuel-based chemicals to biomass-derived products will rely on efficient and cost-effective catalysts that can compete with cheap and readily available fossil fuels. Existing transition and noble metal-based nanoparticle catalysts either in the supported or unsupported form are crippling due to poor activity/selectivity, deactivation of catalytically active sites, and the complex composition, recalcitrant nature, and high moisture content of biomass. Single-atom catalysts (SACs) possessing single-atom centers decorated on support have shown great promise in biomass conversion due to their unique geometric configuration, electronic properties, and ensemble effect. In contrast to traditional catalytic systems, SACs encompass the advantages of both heterogeneous and homogeneous catalysts with improved performance and easy recyclability. Because of the availability of each metal center for the reaction and unique geometrical configuration, SACs have displayed exceptional catalytic activity and selectivity (~95% in most cases). In addition, the SACs show increased thermal and chemical stability due to the stabilization of the metal center on the support. The present chapter highlights the various aspects of SACs for efficient and selective biomass conversion into drop-in chemicals.
This document summarizes research on hydrogen production in Mexico. The main areas of research are: 1) Hydrogen production from biological processes and wastes, which accounts for 40.4% of published papers. 2) Hydrogen production through conventional and non-conventional fuels, along with CO2 capture and catalysis, which accounts for 22.4% of papers. 3) Hydrogen production through photocatalysis and photoelectrocatalysis, which accounts for 14.1% of papers. A wide variety of potential applications could follow from these contributions to strengthen hydrogen research and take advantage of opportunities in Mexico and worldwide.
This document summarizes research on hydrogen production in Mexico. The most active area of research is biological processes, representing 40% of published papers, focusing on topics like bioreactors. The next most active area is catalysis and modified hydrogen processes from conventional sources, representing 22% of papers. Research on photocatalysis and photoelectrocatalysis focuses on developing efficient, stable, and inexpensive photocatalytic materials. Theoretical studies concentrate on optimizing reactor design and evaluating efficiencies. Electrolysis research proposes novel alloys and electrocatalysts. The review aims to assess scientific activity and advances in hydrogen production in Mexico.
HYDROGEN GENERATION FROM WASTE WATER BY USING SOLAR ENERGY | J4RV3I11004Journal For Research
Objective of this paper is to produce hydrogen which is an ideal fuel for the next generation because it is abundantly available in nature, energy efficient and clean. Wide varieties of technologies are available to produce hydrogen but only few of them are considered environmental friendly. Solar water splitting via photo catalytic reaction is one of them which have attracted tremendous attention. In this paper we are working on hydrogen production via solar splitting. Photo catalytic water splitting is one of the promising technologies to produce pure and clean hydrogen. Since it is reasonable having low process cost and has a small reactor, it can be made for house hold application and hence has a huge market potential. Generation of hydrogen under visible irradiation is the main area of work. Based on the literature reported here, visible irradiation can be achieved by doping of TiO2 with metal or non-metal. We have used Fe doping to increase the efficiency. The result indicates that Fe doped sieves produce more hydrogen than the normal TiO2 coated sieve and the efficiency can be increased if we increase the number of doped sieves and surface area.
Nanostructured composite materials for CO2 activationPawan Kumar
This document discusses nanostructured composite materials for CO2 activation, specifically for the photocatalytic reduction of CO2 to valuable products. It provides background on the increasing energy crisis and climate change caused by fossil fuel use. It then summarizes the basic principles and challenges of using semiconductor photocatalysts for CO2 reduction, including appropriate band gap positions and preventing electron-hole recombination. The document discusses various approaches to overcoming these challenges, such as forming heterojunction composites and using co-catalysts to facilitate charge separation and transfer.
Heterojunctions of halogen-doped carbon nitride nanosheets and BiOI for sunli...Pawan Kumar
This document summarizes the synthesis and characterization of halogen-doped carbon nitride nanosheets and BiOI heterojunctions for use in photoelectrochemical water splitting. Specifically:
1) Fluorine-doped, chlorine-intercalated carbon nitride (CNF-Cl) nanosheets were synthesized using thermal annealing to improve light absorption and charge separation.
2) CNF-Cl nanosheets were combined with bismuth oxyiodide (BiOI) nanoplates via a hydrothermal method to form heterojunctions.
3) Characterization using TEM, XRD, Raman and EDS mapping confirmed the formation of CNF-Cl
Water can be split into hydrogen and oxygen through various methods including electrolysis, photolysis, and photoelectrochemical water splitting. Water splitting produces hydrogen which can be used as a renewable fuel and reduces greenhouse gas emissions. Recent research has successfully used an artificial compound called Nafion to split water into hydrogen and oxygen through photoelectrochemical water splitting, demonstrating progress toward replicating natural photosynthesis and providing a clean energy source.
How hydrogen can make india a global energySharon Alex
India has significant potential to become a global leader in hydrogen energy production due to its abundant resources. Hydrogen can be produced from various domestic sources like natural gas, biomass, and increasingly from renewable electricity via electrolysis. It is a clean-burning, high-efficiency fuel that could power vehicles and industries with zero emissions. The Indian government recently announced a green hydrogen mission to boost R&D, create demand, develop industrial applications, and build international partnerships in this area. This could help reduce India's energy import dependence and transition key sectors like steel and transportation to become more sustainable in the long run.
Sustainable Strategies for the Exploitation of End-of-Life Permanent MagnetsNOMADPOWER
Rare Earth Magnets (REM), especially the NdFeB type, are essential components in high-performance electric motors and wind turbines, playing an important role in the shift towards a low-carbon energy matrix. However, little work has been done to understand how the production of REM can be in line with the global sustainable transition. To overcome this lack and help with future research, as well as decision-making, this paper provides a literature overview of which aspects of sustainability are being investigated in the REM supply chain, and how each of them contributes to achieving Sustainable Development Goals (SDG). This research is developed through a consistent analysis of 44 peer-reviewed publications, followed by an analysis of strengths, weaknesses, opportunities, and threats. Four main subjects of studies were identified: environmental impact; social impact; economic aspects and circular economy. Most of the studies focus on computing the environmental impact through life cycle assessment and discussing techniques towards exploring the circular economy concept. In addition to contributing to a greener economy, the majors identified strengths of REM are the great potential of its supply chain in reducing primary resource extraction, since REM recovery and recycling seem to be viable, and the promising techniques to minimize environmental impacts along the rare earth elements production chain.
The document discusses hydrogen fuel cells, including:
1) Hydrogen fuel cells convert chemical energy directly into electrical energy and can provide clean renewable energy for vehicles and stationary power applications.
2) The main methods for producing hydrogen include steam reforming of natural gas, coal gasification, and electrolysis of water. Hydrogen is then stored using compression, liquefaction, or solid-state storage before being delivered via pipelines or cryogenic tanks.
3) Hydrogen is used as fuel in various fuel cell types, with proton exchange membrane fuel cells being a major candidate for automotive use due to their high efficiency and low weight. However, hydrogen fuel cells still face challenges with costs and durability that need to be addressed
Sunlight-driven water-splitting using two dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research
into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of
sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill
the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though
the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their
quantum efficiencies for hydrogen production from visible photons remain too low for the large scale
deployment of this technology. Visible light absorption and efficient charge separation are two key necessary
conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based
nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon
frameworks and their composites have emerged as potential photocatalysts due to their astonishing
properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption,
high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields.
The feasibility of structural and chemical modification to optimize visible light absorption and charge
separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical
energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts
with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported
that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic
catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and
Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a
variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine
hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and
can be recycled up to 10 times without any loss in catalytic activity.
Development of novel catalytic systems for photoreduction of CO2 to fuel and ...Pawan Kumar
This document summarizes the proposed research project on developing novel catalytic systems for the photoreduction of CO2 to fuels and chemicals. The project will focus on using transition metal complexes as photocatalysts immobilized on supporting materials like graphene oxide. Previous work has shown that ruthenium and cobalt complexes immobilized on graphene oxide are effective visible-light active catalysts for reducing CO2 to methanol. The proposed work will synthesize new graphene oxide-supported transition metal complexes and characterize their photocatalytic activity for CO2 reduction.
This document discusses hydrogen production from photocatalytic water splitting using semiconductor materials. It begins by introducing alternative energies and hydrogen as an ideal fuel. It then discusses various methods of hydrogen production, focusing on solar-driven processes like thermochemical, photobiological, and photocatalytic water splitting. The document examines using titanium dioxide (TiO2) as a photocatalyst for water splitting and methods to improve its photoactivity, such as metal loading and doping. It also discusses high-efficiency photocatalytic systems and the types of photocatalytic water splitting reactions. In the end, it emphasizes the need for further research to develop new technologies for low-cost, environmentally friendly hydrogen production.
This document summarizes biological processes for converting carbon dioxide and hydrogen into liquid fuels and chemicals. It discusses several microorganisms and pathways being developed for this purpose, known as "electrofuels". These include Ralstonia eutropha and Clostridium ljungdahlii, which can fix carbon dioxide via the Calvin-Benson-Bassham cycle or Wood-Ljungdahl pathway respectively. The document also reviews computational analyses of carbon fixation pathways and their relative energetic costs for producing biomass and fuels.
Sunlight-driven water-splitting using two-dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their quantum efficiencies for hydrogen production from visible photons remain too low for the large scale deployment of this technology. Visible light absorption and efficient charge separation are two key necessary conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon frameworks and their composites have emerged as potential photocatalysts due to their astonishing properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption, high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields. The feasibility of structural and chemical modification to optimize visible light absorption and charge separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution.
Biohydrogen can be produced through various methods including dark fermentation, photo fermentation, and combined fermentation. Dark fermentation uses fermentative bacteria like Clostridium to convert organic substrates into biohydrogen, carbon dioxide, and organic acids but yields are relatively low. Photo fermentation uses photosynthetic bacteria like Rhodobacter and produces more hydrogen by converting organic acids, while combined fermentation uses a two-stage process to maximize hydrogen yield. Research is ongoing in India to improve production methods and yields through strains isolation, reactor design, and metabolic engineering of bacteria.
E-Waste: Recovery of Precious Materials and Minimization of Environmental Imp...CrimsonpublishersEAES
E-Waste: Recovery of Precious Materials and Minimization of Environmental Impact by Separating Toxic Metals by RK Singhal* in Environmental Analysis & Ecology Studies
Photocatalysis uses light energy to facilitate chemical reactions. Photocatalysts generate holes and electrons when exposed to light that can oxidize or reduce organic matter, breaking it down into carbon dioxide and water. Photocatalysis has applications in renewable energy production like hydrogen fuel from water splitting and reducing carbon dioxide emissions. It can also degrade organic dyes and pollutants in wastewater via generation of radical species during photocatalyst excitation. In conclusion, photocatalysis shows promise as a green technology using sunlight for environmental and energy applications.
High‐efficiency, environment friendly, renewable energy‐based methods of desalination represent attractive and potentially very powerful solutions to the long‐standing problem of global water shortage. Many new laboratory‐scale materials have been developed for photothermal desalination but the development of low‐cost, easy‐to‐manufacture, and scalable materials and systems that can convert solar irradiation into exploitable thermal energy in this context is still a significant challenge. This paper presents work on a geopolymer–biomass mesoporous carbon composite (GBMCC) device with mesoporous and macroporous structures for harvesting solar energy, which is then used in a device to generate water vapor with high efficiency using negative pressure, wind‐driven, steam generation. The GBMCC device gives water evaporation rates of 1.58 and 2.71 kg m−2 h−1 under 1 and 3 suns illumination, with the solar thermal conversion efficiency up to 84.95% and 67.6%, respectively. A remarkable, record high water vapor generation rate of 7.55 kg m−2 h−1 is achieved under 1 sun solar intensity at the wind speed of 3 m s−1. This is a key step forward todays efficient, sustainable and economical production of clean water from seawater or common wastewater with free solar energy. Advanced Functional Materials, Volume28, Issue47, November 21, 2018, 1803266 Pub Date : 2018-11-19 , DOI: 10.1002/adfm.201870332
Fenghua Liu; Binyuan Zhao; Weiping Wu; Haiyan Yang; Yuesheng Ning; Yijian Lai; Robert Bradley. https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201803266
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201870332
The document summarizes different methods for photolysis of water, which is the process of splitting water into hydrogen and oxygen using light. It describes (1) electrolysis, thermal decomposition, photobiological, and photoelectrochemical water splitting. Photoelectrochemical water splitting involves using semiconductors to obtain electrical energy for splitting water. It can use photovoltaic cells, semiconductor-liquid junctions, or a combination. The document also discusses the role of band gaps in metal oxides used as photocatalysts and explains photobiological water splitting using algae. It concludes that hydrogen is a promising fuel that can be obtained through photosplitting of water.
Microbial Disintegration of Bio-Waste for Hydrogen Generation for Application...IRJET Journal
This document discusses methods of producing hydrogen through microbial action on waste biomass as a renewable and cleaner alternative to conventional hydrogen production. It begins with an introduction describing the need for sustainable energy sources and hydrogen fuel cells. The document then reviews biological hydrogen production through various microbial processes including direct and indirect biophotolysis using algae or cyanobacteria, photofermentation using purple bacteria, and dark fermentation. It notes these biological methods can utilize biomass waste as a feedstock while producing hydrogen with lower emissions than natural gas or coal methods. The document focuses on using extreme thermophilic bacteria to efficiently produce hydrogen from renewable resources like crop waste or organic municipal waste.
Cobalt-entrenched N-, O-, and S-tridoped carbons as efficient multifunctional...Pawan Kumar
The document summarizes the synthesis and characterization of a cobalt-entrenched nitrogen-, oxygen-, and sulfur-tridoped carbon catalyst (Co@NOSC) for the base-free selective oxidative esterification of alcohols. The Co@NOSC catalyst was prepared via one-step pyrolysis of carrageenan, urea, and cobalt nitrate, resulting in a cobalt nanoparticle core surrounded by a nitrogen-, oxygen-, and sulfur-rich carbon shell. Characterization showed the catalyst had a cobalt content of 20.89 wt%. The Co@NOSC catalyst achieved excellent conversions (up to 97%) and selectivities (up to 99%) for the base-free oxidative esterification of various al
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
This document provides a comprehensive review of recent advances in catalytic conversion of carbon dioxide to methanol via heterogeneous catalysis. It discusses various catalyst systems that have been developed, including transition metals, metal oxides, main group metals, intermetallic compounds, and nanostructured catalysts derived from metal-organic frameworks. The review emphasizes the importance of understanding structure-activity relationships, reaction mechanisms, and using techniques like in situ characterization and theoretical modeling to guide the design of improved catalysts with good activity, selectivity and stability. While copper-based catalysts have been widely used industrially, the review also covers progress in developing alternative catalyst systems with metals, oxides, main group elements and intermetallics that can help address limitations of
Balucan and Steel_2015_A regenerable precipitant-solvent system for CO2 mitig...Reydick D Balucan
This document describes a new process for CO2 mitigation and metals recovery using a regenerable solvent-precipitant system. The system uses a tertiary amine and acid that can undergo a pH swing via a change in temperature. Specifically, various tertiary amines and acids were tested to identify a combination that can adjust the pH between 10 and 2, which is suitable for metal hydroxide precipitation and metal leaching from magnesium solids. The researchers found that a triethylamine-sulfuric acid-water system could achieve a pH swing between 10.5 and 1.9 with temperature changes, meeting the criteria. This combination uses triethylamine to alkalize the solution to pH > 10.5 and uses sulfur
A closed loop ammonium salt system for recovery of high-purity lead tetroxide...Ary Assuncao
This document describes a closed-loop hydrometallurgical process for recovering high-purity lead tetroxide from spent lead-acid battery paste. The process involves leaching the paste with a mixed solution of ammonium acetate, acetic acid, and hydrogen peroxide. The leachate is then reacted with ammonium carbonate to precipitate lead carbonate. Impurities are removed during leaching and precipitation. The regenerated leachate is recycled for the next leaching. Lead carbonate is calcined to produce lead tetroxide with low impurity levels meeting industry standards. This process allows for reagent recirculation and production of a high value lead recovery product.
Heterojunctions of halogen-doped carbon nitride nanosheets and BiOI for sunli...Pawan Kumar
This document summarizes the synthesis and characterization of halogen-doped carbon nitride nanosheets and BiOI heterojunctions for use in photoelectrochemical water splitting. Specifically:
1) Fluorine-doped, chlorine-intercalated carbon nitride (CNF-Cl) nanosheets were synthesized using thermal annealing to improve light absorption and charge separation.
2) CNF-Cl nanosheets were combined with bismuth oxyiodide (BiOI) nanoplates via a hydrothermal method to form heterojunctions.
3) Characterization using TEM, XRD, Raman and EDS mapping confirmed the formation of CNF-Cl
Water can be split into hydrogen and oxygen through various methods including electrolysis, photolysis, and photoelectrochemical water splitting. Water splitting produces hydrogen which can be used as a renewable fuel and reduces greenhouse gas emissions. Recent research has successfully used an artificial compound called Nafion to split water into hydrogen and oxygen through photoelectrochemical water splitting, demonstrating progress toward replicating natural photosynthesis and providing a clean energy source.
How hydrogen can make india a global energySharon Alex
India has significant potential to become a global leader in hydrogen energy production due to its abundant resources. Hydrogen can be produced from various domestic sources like natural gas, biomass, and increasingly from renewable electricity via electrolysis. It is a clean-burning, high-efficiency fuel that could power vehicles and industries with zero emissions. The Indian government recently announced a green hydrogen mission to boost R&D, create demand, develop industrial applications, and build international partnerships in this area. This could help reduce India's energy import dependence and transition key sectors like steel and transportation to become more sustainable in the long run.
Sustainable Strategies for the Exploitation of End-of-Life Permanent MagnetsNOMADPOWER
Rare Earth Magnets (REM), especially the NdFeB type, are essential components in high-performance electric motors and wind turbines, playing an important role in the shift towards a low-carbon energy matrix. However, little work has been done to understand how the production of REM can be in line with the global sustainable transition. To overcome this lack and help with future research, as well as decision-making, this paper provides a literature overview of which aspects of sustainability are being investigated in the REM supply chain, and how each of them contributes to achieving Sustainable Development Goals (SDG). This research is developed through a consistent analysis of 44 peer-reviewed publications, followed by an analysis of strengths, weaknesses, opportunities, and threats. Four main subjects of studies were identified: environmental impact; social impact; economic aspects and circular economy. Most of the studies focus on computing the environmental impact through life cycle assessment and discussing techniques towards exploring the circular economy concept. In addition to contributing to a greener economy, the majors identified strengths of REM are the great potential of its supply chain in reducing primary resource extraction, since REM recovery and recycling seem to be viable, and the promising techniques to minimize environmental impacts along the rare earth elements production chain.
The document discusses hydrogen fuel cells, including:
1) Hydrogen fuel cells convert chemical energy directly into electrical energy and can provide clean renewable energy for vehicles and stationary power applications.
2) The main methods for producing hydrogen include steam reforming of natural gas, coal gasification, and electrolysis of water. Hydrogen is then stored using compression, liquefaction, or solid-state storage before being delivered via pipelines or cryogenic tanks.
3) Hydrogen is used as fuel in various fuel cell types, with proton exchange membrane fuel cells being a major candidate for automotive use due to their high efficiency and low weight. However, hydrogen fuel cells still face challenges with costs and durability that need to be addressed
Sunlight-driven water-splitting using two dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research
into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of
sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill
the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though
the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their
quantum efficiencies for hydrogen production from visible photons remain too low for the large scale
deployment of this technology. Visible light absorption and efficient charge separation are two key necessary
conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based
nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon
frameworks and their composites have emerged as potential photocatalysts due to their astonishing
properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption,
high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields.
The feasibility of structural and chemical modification to optimize visible light absorption and charge
separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical
energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts
with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution
Synthesis of flower-like magnetite nanoassembly: Application in the efficient...Pawan Kumar
A facile approach for the synthesis of magnetite microspheres with flower-like morphology is reported
that proceeds via the reduction of iron(III) oxide under a hydrogen atmosphere. The ensuing magnetic
catalyst is well characterized by XRD, FE-SEM, TEM, N2 adsorption-desorption isotherm, and
Mössbauer spectroscopy and explored for a simple yet efficient transfer hydrogenation reduction of a
variety of nitroarenes to respective anilines in good to excellent yields (up to 98%) employing hydrazine
hydrate. The catalyst could be easily separated at the end of a reaction using an external magnet and
can be recycled up to 10 times without any loss in catalytic activity.
Development of novel catalytic systems for photoreduction of CO2 to fuel and ...Pawan Kumar
This document summarizes the proposed research project on developing novel catalytic systems for the photoreduction of CO2 to fuels and chemicals. The project will focus on using transition metal complexes as photocatalysts immobilized on supporting materials like graphene oxide. Previous work has shown that ruthenium and cobalt complexes immobilized on graphene oxide are effective visible-light active catalysts for reducing CO2 to methanol. The proposed work will synthesize new graphene oxide-supported transition metal complexes and characterize their photocatalytic activity for CO2 reduction.
This document discusses hydrogen production from photocatalytic water splitting using semiconductor materials. It begins by introducing alternative energies and hydrogen as an ideal fuel. It then discusses various methods of hydrogen production, focusing on solar-driven processes like thermochemical, photobiological, and photocatalytic water splitting. The document examines using titanium dioxide (TiO2) as a photocatalyst for water splitting and methods to improve its photoactivity, such as metal loading and doping. It also discusses high-efficiency photocatalytic systems and the types of photocatalytic water splitting reactions. In the end, it emphasizes the need for further research to develop new technologies for low-cost, environmentally friendly hydrogen production.
This document summarizes biological processes for converting carbon dioxide and hydrogen into liquid fuels and chemicals. It discusses several microorganisms and pathways being developed for this purpose, known as "electrofuels". These include Ralstonia eutropha and Clostridium ljungdahlii, which can fix carbon dioxide via the Calvin-Benson-Bassham cycle or Wood-Ljungdahl pathway respectively. The document also reviews computational analyses of carbon fixation pathways and their relative energetic costs for producing biomass and fuels.
Sunlight-driven water-splitting using two-dimensional carbon based semiconduc...Pawan Kumar
The overwhelming challenge of depleting fossil fuels and anthropogenic carbon emissions has driven research into alternative clean sources of energy. To achieve the goal of a carbon neutral economy, the harvesting of sunlight by using photocatalysts to split water into hydrogen and oxygen is an expedient approach to fulfill the energy demand in a sustainable way along with reducing the emission of greenhouse gases. Even though the past few decades have witnessed intensive research into inorganic semiconductor photocatalysts, their quantum efficiencies for hydrogen production from visible photons remain too low for the large scale deployment of this technology. Visible light absorption and efficient charge separation are two key necessary conditions for achieving the scalable production of hydrogen from water. Two-dimensional carbon based nanoscale materials such as graphene oxide, reduced graphene oxide, carbon nitride, modified 2D carbon frameworks and their composites have emerged as potential photocatalysts due to their astonishing properties such as superior charge transport, tunable energy levels and bandgaps, visible light absorption, high surface area, easy processability, quantum confinement effects, and high photocatalytic quantum yields. The feasibility of structural and chemical modification to optimize visible light absorption and charge separation makes carbonaceous semiconductors promising candidates to convert solar energy into chemical energy. In the present review, we have summarized the recent advances in 2D carbonaceous photocatalysts with respect to physicochemical and photochemical tuning for solar light mediated hydrogen evolution.
Biohydrogen can be produced through various methods including dark fermentation, photo fermentation, and combined fermentation. Dark fermentation uses fermentative bacteria like Clostridium to convert organic substrates into biohydrogen, carbon dioxide, and organic acids but yields are relatively low. Photo fermentation uses photosynthetic bacteria like Rhodobacter and produces more hydrogen by converting organic acids, while combined fermentation uses a two-stage process to maximize hydrogen yield. Research is ongoing in India to improve production methods and yields through strains isolation, reactor design, and metabolic engineering of bacteria.
E-Waste: Recovery of Precious Materials and Minimization of Environmental Imp...CrimsonpublishersEAES
E-Waste: Recovery of Precious Materials and Minimization of Environmental Impact by Separating Toxic Metals by RK Singhal* in Environmental Analysis & Ecology Studies
Photocatalysis uses light energy to facilitate chemical reactions. Photocatalysts generate holes and electrons when exposed to light that can oxidize or reduce organic matter, breaking it down into carbon dioxide and water. Photocatalysis has applications in renewable energy production like hydrogen fuel from water splitting and reducing carbon dioxide emissions. It can also degrade organic dyes and pollutants in wastewater via generation of radical species during photocatalyst excitation. In conclusion, photocatalysis shows promise as a green technology using sunlight for environmental and energy applications.
High‐efficiency, environment friendly, renewable energy‐based methods of desalination represent attractive and potentially very powerful solutions to the long‐standing problem of global water shortage. Many new laboratory‐scale materials have been developed for photothermal desalination but the development of low‐cost, easy‐to‐manufacture, and scalable materials and systems that can convert solar irradiation into exploitable thermal energy in this context is still a significant challenge. This paper presents work on a geopolymer–biomass mesoporous carbon composite (GBMCC) device with mesoporous and macroporous structures for harvesting solar energy, which is then used in a device to generate water vapor with high efficiency using negative pressure, wind‐driven, steam generation. The GBMCC device gives water evaporation rates of 1.58 and 2.71 kg m−2 h−1 under 1 and 3 suns illumination, with the solar thermal conversion efficiency up to 84.95% and 67.6%, respectively. A remarkable, record high water vapor generation rate of 7.55 kg m−2 h−1 is achieved under 1 sun solar intensity at the wind speed of 3 m s−1. This is a key step forward todays efficient, sustainable and economical production of clean water from seawater or common wastewater with free solar energy. Advanced Functional Materials, Volume28, Issue47, November 21, 2018, 1803266 Pub Date : 2018-11-19 , DOI: 10.1002/adfm.201870332
Fenghua Liu; Binyuan Zhao; Weiping Wu; Haiyan Yang; Yuesheng Ning; Yijian Lai; Robert Bradley. https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201803266
https://onlinelibrary.wiley.com/doi/abs/10.1002/adfm.201870332
The document summarizes different methods for photolysis of water, which is the process of splitting water into hydrogen and oxygen using light. It describes (1) electrolysis, thermal decomposition, photobiological, and photoelectrochemical water splitting. Photoelectrochemical water splitting involves using semiconductors to obtain electrical energy for splitting water. It can use photovoltaic cells, semiconductor-liquid junctions, or a combination. The document also discusses the role of band gaps in metal oxides used as photocatalysts and explains photobiological water splitting using algae. It concludes that hydrogen is a promising fuel that can be obtained through photosplitting of water.
Microbial Disintegration of Bio-Waste for Hydrogen Generation for Application...IRJET Journal
This document discusses methods of producing hydrogen through microbial action on waste biomass as a renewable and cleaner alternative to conventional hydrogen production. It begins with an introduction describing the need for sustainable energy sources and hydrogen fuel cells. The document then reviews biological hydrogen production through various microbial processes including direct and indirect biophotolysis using algae or cyanobacteria, photofermentation using purple bacteria, and dark fermentation. It notes these biological methods can utilize biomass waste as a feedstock while producing hydrogen with lower emissions than natural gas or coal methods. The document focuses on using extreme thermophilic bacteria to efficiently produce hydrogen from renewable resources like crop waste or organic municipal waste.
Cobalt-entrenched N-, O-, and S-tridoped carbons as efficient multifunctional...Pawan Kumar
The document summarizes the synthesis and characterization of a cobalt-entrenched nitrogen-, oxygen-, and sulfur-tridoped carbon catalyst (Co@NOSC) for the base-free selective oxidative esterification of alcohols. The Co@NOSC catalyst was prepared via one-step pyrolysis of carrageenan, urea, and cobalt nitrate, resulting in a cobalt nanoparticle core surrounded by a nitrogen-, oxygen-, and sulfur-rich carbon shell. Characterization showed the catalyst had a cobalt content of 20.89 wt%. The Co@NOSC catalyst achieved excellent conversions (up to 97%) and selectivities (up to 99%) for the base-free oxidative esterification of various al
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...Pawan Kumar
Photonic crystals consisting of TiO2 nanotube arrays (PMTiNTs) with periodically modulated diameters were fabricated using a precise charge-controlled pulsed anodization technique. The PMTiNTs were decorated with gold nanoparticles (Au NPs) to form plasmonic photonic crystal photocatalysts (Au-PMTiNTs). A systematic study of CO2 photoreduction performance on as-prepared samples was conducted using different wavelengths and illumination sequences. A remarkable selectivity of the mechanism of CO2 photoreduction could be engineered by merely varying the spectral composition of the illumination sequence. Under AM1.5 G simulated sunlight (pathway#1), the Au-PMTiNTs produced methane (302 µmol h-1) from CO2 with high selectivity (89.3%). When also illuminated by a UV-poor white lamp (pathway#2), the Au-PMTiNTs produced formaldehyde (420 µmol h-1) and carbon monoxide (323 µmol h-1) with almost no methane evolved. We confirmed the photoreduction results by 13C isotope labeling experiments using GC-MS. These results point to optical control of the selectivity of high-rate CO2 photoreduction through selection of one of two different mechanistic pathways. Pathway#1 implicates electron-hole pairs generated through interband transitions in TiO2 and Au as the primary active species responsible for reducing CO2 to methane. Pathway#2 involves excitation of both TiO2 and surface plasmons in Au. Hot electrons produced by plasmon damping and photogenerated holes in TiO2 proceed to reduce CO2 to HCHO and CO through a plasmonic Z-scheme.
Optical Control of Selectivity of High Rate CO2 Photoreduction Via Interband-...
Similar to Dry Grinding - Carbonated Ultrasound-Assisted Water Leaching of Carbothermally Reduced Lithium-Ion Battery Black Mass Towards Enhanced Selective Extraction of Lithium and Recovery of High-Value Metals.pdf
This document provides a comprehensive review of recent advances in catalytic conversion of carbon dioxide to methanol via heterogeneous catalysis. It discusses various catalyst systems that have been developed, including transition metals, metal oxides, main group metals, intermetallic compounds, and nanostructured catalysts derived from metal-organic frameworks. The review emphasizes the importance of understanding structure-activity relationships, reaction mechanisms, and using techniques like in situ characterization and theoretical modeling to guide the design of improved catalysts with good activity, selectivity and stability. While copper-based catalysts have been widely used industrially, the review also covers progress in developing alternative catalyst systems with metals, oxides, main group elements and intermetallics that can help address limitations of
Balucan and Steel_2015_A regenerable precipitant-solvent system for CO2 mitig...Reydick D Balucan
This document describes a new process for CO2 mitigation and metals recovery using a regenerable solvent-precipitant system. The system uses a tertiary amine and acid that can undergo a pH swing via a change in temperature. Specifically, various tertiary amines and acids were tested to identify a combination that can adjust the pH between 10 and 2, which is suitable for metal hydroxide precipitation and metal leaching from magnesium solids. The researchers found that a triethylamine-sulfuric acid-water system could achieve a pH swing between 10.5 and 1.9 with temperature changes, meeting the criteria. This combination uses triethylamine to alkalize the solution to pH > 10.5 and uses sulfur
A closed loop ammonium salt system for recovery of high-purity lead tetroxide...Ary Assuncao
This document describes a closed-loop hydrometallurgical process for recovering high-purity lead tetroxide from spent lead-acid battery paste. The process involves leaching the paste with a mixed solution of ammonium acetate, acetic acid, and hydrogen peroxide. The leachate is then reacted with ammonium carbonate to precipitate lead carbonate. Impurities are removed during leaching and precipitation. The regenerated leachate is recycled for the next leaching. Lead carbonate is calcined to produce lead tetroxide with low impurity levels meeting industry standards. This process allows for reagent recirculation and production of a high value lead recovery product.
Nanostructured composite materials for CO2 activationPawan Kumar
This document summarizes the challenges of rising CO2 levels and discusses nanostructured composite materials for CO2 activation. It notes that CO2 levels are the highest in 800,000 years due to fossil fuel use. While CO2 storage is possible, conversion to chemicals is promising. Semiconductors can photocatalytically reduce CO2 but require visible light absorption and charge separation to be efficient. The document reviews the thermodynamics of CO2 reduction and discusses producing hydrogen from water splitting to enable CO2 conversion to hydrocarbons like methanol.
1) The document discusses various methods for converting carbon dioxide (CO2) into valuable products and fuels to reduce CO2 emissions, including chemical looping combustion, CO2 conversion to fuels using chromium supports, burning magnesium metal in dry ice to produce graphene, electrochemical conversion to methanol and ethanol, and conversion using solar energy.
2) It reviews literature on these conversion methods and their products, like oxygen and fuels via chemical looping, alcohols using chromium-doped titanium supports, and graphene from burning magnesium in dry ice.
3) The effects of increased CO2 levels on humans, the environment, climate change and ocean acidification are also summarized. Converting CO2 into valuable fuels and chemicals using various catalytic
Lithium recovery from spent Li-ion batteries using coconut shell activated ca...UniversitasGadjahMada
Lithium is one of scarce natural resources in the world that need to be preserve. One of the way in preserving the resource is by recovery the rich source of the lithium such as in the spent batteries. It is necessary to develop a recovery method which is efficient and low-cost to be able to recover the lithium in an economic scale. In this study, low-cost activated carbon (AC) from coconut shell charcoal was prepared by chemical and physical activation methods and tested for Li removal from Co, Mn, and Ni ions in semicontinuous columns adsorption experiments. The maximum surface area is 365 m2/g with the total pore volume is 0.148 cm3/g that can be produced by physical activation at 800 °C. In the same activation temperature, activation using KOH has larger ratio of micropore volume than physical activation. Then, the adsorption capacity and selectivity of metal ions were investigated. A very low adsorption capacity of AC for Li ions in batch adsorption mode provides an advantage in column applications for separating Li from other metal ions. The AC sample with chemical activation provided better separation than the samples with physical activation in the column adsorption method. During a certain period of early adsorption (lag time), solution collected from the column outlet was found to be rich in Li due to the fast travel time of this light element, while the other heavier metal ions were mostly retained in the AC bed. The maximum lag time is 97.3 min with AC by KOH activation at 750°C.
Metal Oxides as Catalyst/Supporter for CO2 Capture and Conversionssuser7bc3591
Various carbon dioxide (CO2) capture materials and processes have been developed in recent years. The absorption-based capturing process is the most significant among other processes, which is widely recognized because of its effectiveness. CO2 can be used as a feedstock for the production of valuable chemicals, which will assist in alleviating the issues caused by excessive CO2 levels in the atmosphere. However, the interaction of carbon dioxide with other substances is laborious because carbon dioxide is dynamically relatively stable. Therefore, there is a need to develop types of catalysts that can break the bond in CO2 and thus be used as feedstock to produce materials of economic value. Metal oxide-based processes that convert carbon dioxide into other compounds have recently attracted attention. Metal oxides play a pivotal role in CO2 hydrogenation, as they provide additional advantages, such as selectivity and energy efficiency. This review provides an overview of the types of metal oxides and their use for carbon dioxide adsorption and conversion applications, allowing researchers to take advantage of this information in order to develop new catalysts or methods for preparing catalysts to obtain materials of economic value.
This document describes the synthesis and characterization of a core-shell structured reduced graphene oxide wrapped magnetically separable rGO@CuZnO@Fe3O4 microspheres photocatalyst and its use for the photoreduction of carbon dioxide to methanol under visible light irradiation. The photocatalyst takes advantage of the high photocatalytic efficiency of zinc oxide, the high surface area and charge carrier mobility of reduced graphene oxide, and the magnetic properties of an iron oxide core. Experimental results showed the rGO@CuZnO@Fe3O4 photocatalyst had higher catalytic activity than other possible combinations, with a methanol yield of 2656 μmol/gcat under visible light, and could be readily recovered and
This document summarizes a study that evaluated factors influencing the production of sodium hydroxide (NaOH) using an ion exchange membrane electrolytic cell. The study tested different initial NaOH concentrations, applied voltages, and temperatures. Experiments used a model NaCl solution and measured changes in NaOH concentration, conductivity, and pH over 150 minutes. Results showed these parameters increased linearly with electrolysis time. The current efficiency was on average 80.2%, indicating good cell performance.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
Reduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
Reduced graphene oxide–CuO nanocomposites for photocatalyticconversion of CO2...Pawan Kumar
tReduced graphene oxide (rGO)–copper oxide nanocomposites are prepared by covalent grafting of CuOnanorods on the rGO skeleton. Chemical and structural features of rGO–CuO nanocomposites are probedby FTIR, XPS, XRD and HRTEM analyses. Photocatalytic potential of rGO–CuO nanocomposites is exploredfor reduction of CO2into the methanol under the visible light irradiation. The breadth of CuO nanorods andthe oxidation state of Cu in the rGO–CuO/Cu2O nanocomposites are systematically varied to investigatetheir photocatalytic activities. The pristine CuO nanorods exhibited very low photocatalytic activity owingto fast recombination of charge carriers and yielded 175 mol g−1methanol, whereas rGO–Cu2O andrGO–CuO exhibited significantly improved photocatalytic activities and yielded five (862 mol g−1) andseven (1228 mol g−1) folds methanol, respectively. The superior photocatalytic activity of CuO in therGO–CuO nanocomposites was attributed to slow recombination of charge carriers and efficient transferof photo-generated electrons through the rGO skeleton. This study further excludes the use of scavengingdonor.
High rate CO2 photoreduction using flame annealed TiO2 nanotubesPawan Kumar
The photocatalytic reduction of CO2 into light hydrocarbons using sunlight and water is a challenging reaction involving eight electron transfer steps; nevertheless, it has great potential to address the problem of rising anthropogenic carbon emissions and enable the use of fossil fuels in a sustainable way. Several decades after its first use, TiO2 remains one of the best performing and most durable photocatalysts for CO2 reduction albeit with a poor visible light absorption capacity. We have used flame annealing to improve the response of TiO2 to visible photons and engineered a nanotubular morphology with square-shaped cross-sections in flame-annealed nanotubes. An enhanced CH4 yield was achieved in the photoreduction of CO2 using flame annealed TiO2 nanotubes, and isotope labeled experiments confirmed the reaction products to originate from the CO2 reactant. Flame-annealed TiO2 nanotubes formed in aqueous electrolyte (FANT-aq) yielded 156.5 μmol gcatalyst–1.hr–1 of CH4, which is in the top tier of reported performance values achieved using TiO2 as a stand-alone photocatalyst. This performance resulted because appreciable amounts of CH4 were generated under visible light illumination as well. TiO2 nanotubes exhibited CO2 photoreduction activity up to a wavelength of 620 nm with visible light driven photocatalytic activity peaking at 450 nm for flame annealed TiO2 nanotubes. Isotope labelling studies, using GC–MS and gas-phase FTIR, indicated photoreduction of 13CO2 to 13CH4. The detection of 13CO in the product mixture, and the absence of HCHO and HCOOH provides strong support for the photoreduction proceeding along a carbene pathway. The enhanced CO2 photoreduction performance of FANT-aq is attributed to increased visible light absorption, square morphology, and the presence of rutile as the only crystalline phase with (110) as the dominant plane.
High rate CO2 photoreduction using flame annealed TiO2 nanotubesPawan Kumar
The photocatalytic reduction of CO2 into light hydrocarbons using sunlight and water is a challenging reaction involving eight electron transfer steps; nevertheless, it has great potential to address the problem of rising anthropogenic carbon emissions and enable the use of fossil fuels in a sustainable way. Several decades after its first use, TiO2 remains one of the best performing and most durable photocatalysts for CO2 reduction albeit with a poor visible light absorption capacity. We have used flame annealing to improve the response of TiO2 to visible photons and engineered a nanotubular morphology with square-shaped cross-sections in flame-annealed nanotubes. An enhanced CH4 yield was achieved in the photoreduction of CO2 using flame annealed TiO2 nanotubes, and isotope labeled experiments confirmed the reaction products to originate from the CO2 reactant. Flame-annealed TiO2 nanotubes
Visible light assisted hydrogen generation from complete decomposition of hyd...Pawan Kumar
Hydrogen is considered to be an ideal energy carrier, which produces only water when combined with
oxygen and thus has no detrimental effect on the environment. While the catalytic decomposition of
hydrous hydrazine for the production of hydrogen is well explored, little is known about its photocatalytic
decomposition. The present paper describes a highly efficient photochemical methodology for the production
of hydrogen through the decomposition of aqueous hydrazine using titanium dioxide nanoparticles
modified with a Rh(I) coordinated catechol phosphane ligand (TiO2–Rh) as a photocatalyst under visible
light irradiation. After 12 h of visible light irradiation, the hydrogen yield was 413 μmol g−1 cat with a hydrogen
evolution rate of 34.4 μmol g−1 cat h−1. Unmodified TiO2 nanoparticles offered a hydrogen yield of
83 μmol g−1 cat and a hydrogen evolution rate of only 6.9 μmol g−1 cat h−1. The developed photocatalyst
was robust under the experimental conditions and could be efficiently reused for five subsequent runs
without any significant change in its activity. The higher stability of the photocatalyst is attributed to the
covalent attachment of the Rh complex, whereas the higher activity is believed to be due to the synergistic
mechanism that resulted in better electron transfer from the Rh complex to the conduction band of TiO2
Hexamolybdenum clusters supported on graphene oxide: Visible-light induced ph...Pawan Kumar
Hexamolybdenum (Mo6) cluster-based compounds namely Cs2Mo6Bri
8Bra6
and
(TBA)2Mo6Bri
8Bra
6 (TBA = tetrabutylammonium) were immobilized on graphene oxide (GO)
nanosheets by taking advantage of the high lability of the apical bromide ions with
oxygen-functionalities of GO nanosheets. The loading of Mo6 clusters on GO nanosheets
was probed by Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron
spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and elemental
mapping analyses. The developed GO-Cs2Mo6Bri
8Bra
x and GO-(TBA)2Mo6Bri
8Bra
x
composites were then used as heterogeneous photocatalysts for the reduction of CO2 under
visible light irradiation. After 24 h visible light illumination, the yield of methanol was
found to be 1644 and 1294 lmol g1 cat for GO-Cs2Mo6Bri
8Bra
x and GO-(TBA)2Mo6Bri
8Bra
x,
respectively. The quantum yields of methanol by using GO-Cs2Mo6Bri
8Bra
x and
GO-(TBA)2Mo6Bri
8Bra
x as catalysts with reference to Mo6 cluster units presented in 0.1 g
amount of catalyst were found to be 0.015 and 0.011, respectively. The role of immobilized
Mo6 clusters-based compounds on GO nanosheets is discussed to understand the
photocatalytic mechanism of CO2 reduction into methanol.
Hexamolybdenum clusters supported on graphene oxide: Visible-light induced ph...Pawan Kumar
This document summarizes a study on immobilizing hexamolybdenum clusters on graphene oxide nanosheets for photocatalytic reduction of carbon dioxide into methanol. Specifically, Cs2Mo6Bri8Bra6 and (TBA)2Mo6Bri8Bra6 clusters were immobilized on graphene oxide through replacement of apical bromide ions with oxygen functional groups on the graphene oxide surface. The developed GO-Cs2Mo6Bri8Brax and GO-(TBA)2Mo6Bri8Brax composites were then used as heterogeneous photocatalysts for CO2 reduction under visible light, producing methanol yields of 1644 and 1294 μmol g−1cat, respectively
Single Atom Catalysts for Selective Methane Oxidation to OxygenatesPawan Kumar
Direct conversion of methane (CH4) to C1–2 liquid oxygenates is a captivating approach to lock carbons in transportable value-added chemicals, while reducing global warming. Existing approaches utilizing the transformation of CH4 to liquid fuel via tandemized steam methane reforming and the Fischer–Tropsch synthesis are energy and capital intensive. Chemocatalytic partial oxidation of methane remains challenging due to the negligible electron affinity, poor C–H bond polarizability, and high activation energy barrier. Transition-metal and stoichiometric catalysts utilizing harsh oxidants and reaction conditions perform poorly with randomized product distribution. Paradoxically, the catalysts which are active enough to break C–H also promote overoxidation, resulting in CO2 generation and reduced carbon balance. Developing catalysts which can break C–H bonds of methane to selectively make useful chemicals at mild conditions is vital to commercialization. Single atom catalysts (SACs) with specifically coordinated metal centers on active support have displayed intrigued reactivity and selectivity for methane oxidation. SACs can significantly reduce the activation energy due to induced electrostatic polarization of the C–H bond to facilitate the accelerated reaction rate at the low reaction temperature. The distinct metal–support interaction can stabilize the intermediate and prevent the overoxidation of the reaction products. The present review accounts for recent progress in the field of SACs for the selective oxidation of CH4 to C1–2 oxygenates. The chemical nature of catalytic sites, effects of metal–support interaction, and stabilization of intermediate species on catalysts to minimize overoxidation are thoroughly discussed with a forward-looking perspective to improve the catalytic performance.
nano catalysis as a prospectus of green chemistry Ankit Grover
Nanocatalysis and green chemistry prospects.
Nanocatalysts have higher activity, selectivity, and efficiency than traditional catalysts due to their high surface area to volume ratio. They can be designed for sustainability by having properties like recyclability, durability, and cost-effectiveness. Examples discussed include gold nanoparticle catalysts for oxidation reactions and magnetically separable nanoparticle catalysts. Nanocatalyst applications highlighted are water splitting for hydrogen production and storage, and fuel cells.
This document describes a hydrometallurgical process for recovering rare earth elements from spent nickel-metal hydride batteries. The process involves three steps:
1) Leaching electrode materials from the batteries in sulfuric acid solutions using ozone as the oxidant, which achieved over 90% recovery of lanthanum, cerium, and neodymium.
2) Separating cobalt and part of the nickel from the leach solution using electrodeposition in an electrochemical reactor.
3) Precipitating the remaining rare earth elements along with the rest of the nickel by adjusting the pH of the solution.
This document summarizes a project studying the use of red mud and pure metal oxides as potential catalysts for hydrothermal liquefaction (HTL) of food waste. The goal is to find a cheaper alternative to the commercial Ceria Zirconia catalyst. HTL converts biomass into liquid biofuel using water at high pressure and temperature. Previous studies show Ceria Zirconia improves biooil yield but is costly to reuse. Red mud, a low-cost byproduct, contains metal oxides that could achieve the desired base chemistry. The project will compare the impact of red mud and pure metal oxide catalysts to Ceria Zirconia on biooil production from food waste.
Similar to Dry Grinding - Carbonated Ultrasound-Assisted Water Leaching of Carbothermally Reduced Lithium-Ion Battery Black Mass Towards Enhanced Selective Extraction of Lithium and Recovery of High-Value Metals.pdf (20)
Harnessing WebAssembly for Real-time Stateless Streaming PipelinesChristina Lin
Traditionally, dealing with real-time data pipelines has involved significant overhead, even for straightforward tasks like data transformation or masking. However, in this talk, we’ll venture into the dynamic realm of WebAssembly (WASM) and discover how it can revolutionize the creation of stateless streaming pipelines within a Kafka (Redpanda) broker. These pipelines are adept at managing low-latency, high-data-volume scenarios.
A SYSTEMATIC RISK ASSESSMENT APPROACH FOR SECURING THE SMART IRRIGATION SYSTEMSIJNSA Journal
The smart irrigation system represents an innovative approach to optimize water usage in agricultural and landscaping practices. The integration of cutting-edge technologies, including sensors, actuators, and data analysis, empowers this system to provide accurate monitoring and control of irrigation processes by leveraging real-time environmental conditions. The main objective of a smart irrigation system is to optimize water efficiency, minimize expenses, and foster the adoption of sustainable water management methods. This paper conducts a systematic risk assessment by exploring the key components/assets and their functionalities in the smart irrigation system. The crucial role of sensors in gathering data on soil moisture, weather patterns, and plant well-being is emphasized in this system. These sensors enable intelligent decision-making in irrigation scheduling and water distribution, leading to enhanced water efficiency and sustainable water management practices. Actuators enable automated control of irrigation devices, ensuring precise and targeted water delivery to plants. Additionally, the paper addresses the potential threat and vulnerabilities associated with smart irrigation systems. It discusses limitations of the system, such as power constraints and computational capabilities, and calculates the potential security risks. The paper suggests possible risk treatment methods for effective secure system operation. In conclusion, the paper emphasizes the significant benefits of implementing smart irrigation systems, including improved water conservation, increased crop yield, and reduced environmental impact. Additionally, based on the security analysis conducted, the paper recommends the implementation of countermeasures and security approaches to address vulnerabilities and ensure the integrity and reliability of the system. By incorporating these measures, smart irrigation technology can revolutionize water management practices in agriculture, promoting sustainability, resource efficiency, and safeguarding against potential security threats.
International Conference on NLP, Artificial Intelligence, Machine Learning an...gerogepatton
International Conference on NLP, Artificial Intelligence, Machine Learning and Applications (NLAIM 2024) offers a premier global platform for exchanging insights and findings in the theory, methodology, and applications of NLP, Artificial Intelligence, Machine Learning, and their applications. The conference seeks substantial contributions across all key domains of NLP, Artificial Intelligence, Machine Learning, and their practical applications, aiming to foster both theoretical advancements and real-world implementations. With a focus on facilitating collaboration between researchers and practitioners from academia and industry, the conference serves as a nexus for sharing the latest developments in the field.
Low power architecture of logic gates using adiabatic techniquesnooriasukmaningtyas
The growing significance of portable systems to limit power consumption in ultra-large-scale-integration chips of very high density, has recently led to rapid and inventive progresses in low-power design. The most effective technique is adiabatic logic circuit design in energy-efficient hardware. This paper presents two adiabatic approaches for the design of low power circuits, modified positive feedback adiabatic logic (modified PFAL) and the other is direct current diode based positive feedback adiabatic logic (DC-DB PFAL). Logic gates are the preliminary components in any digital circuit design. By improving the performance of basic gates, one can improvise the whole system performance. In this paper proposed circuit design of the low power architecture of OR/NOR, AND/NAND, and XOR/XNOR gates are presented using the said approaches and their results are analyzed for powerdissipation, delay, power-delay-product and rise time and compared with the other adiabatic techniques along with the conventional complementary metal oxide semiconductor (CMOS) designs reported in the literature. It has been found that the designs with DC-DB PFAL technique outperform with the percentage improvement of 65% for NOR gate and 7% for NAND gate and 34% for XNOR gate over the modified PFAL techniques at 10 MHz respectively.
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Embedded machine learning-based road conditions and driving behavior monitoringIJECEIAES
Car accident rates have increased in recent years, resulting in losses in human lives, properties, and other financial costs. An embedded machine learning-based system is developed to address this critical issue. The system can monitor road conditions, detect driving patterns, and identify aggressive driving behaviors. The system is based on neural networks trained on a comprehensive dataset of driving events, driving styles, and road conditions. The system effectively detects potential risks and helps mitigate the frequency and impact of accidents. The primary goal is to ensure the safety of drivers and vehicles. Collecting data involved gathering information on three key road events: normal street and normal drive, speed bumps, circular yellow speed bumps, and three aggressive driving actions: sudden start, sudden stop, and sudden entry. The gathered data is processed and analyzed using a machine learning system designed for limited power and memory devices. The developed system resulted in 91.9% accuracy, 93.6% precision, and 92% recall. The achieved inference time on an Arduino Nano 33 BLE Sense with a 32-bit CPU running at 64 MHz is 34 ms and requires 2.6 kB peak RAM and 139.9 kB program flash memory, making it suitable for resource-constrained embedded systems.
KuberTENes Birthday Bash Guadalajara - K8sGPT first impressionsVictor Morales
K8sGPT is a tool that analyzes and diagnoses Kubernetes clusters. This presentation was used to share the requirements and dependencies to deploy K8sGPT in a local environment.
A review on techniques and modelling methodologies used for checking electrom...nooriasukmaningtyas
The proper function of the integrated circuit (IC) in an inhibiting electromagnetic environment has always been a serious concern throughout the decades of revolution in the world of electronics, from disjunct devices to today’s integrated circuit technology, where billions of transistors are combined on a single chip. The automotive industry and smart vehicles in particular, are confronting design issues such as being prone to electromagnetic interference (EMI). Electronic control devices calculate incorrect outputs because of EMI and sensors give misleading values which can prove fatal in case of automotives. In this paper, the authors have non exhaustively tried to review research work concerned with the investigation of EMI in ICs and prediction of this EMI using various modelling methodologies and measurement setups.
A review on techniques and modelling methodologies used for checking electrom...
Dry Grinding - Carbonated Ultrasound-Assisted Water Leaching of Carbothermally Reduced Lithium-Ion Battery Black Mass Towards Enhanced Selective Extraction of Lithium and Recovery of High-Value Metals.pdf
2. Resources, Conservation & Recycling 174 (2021) 105784
2
and recovery techniques such as selective precipitation, ion exchange,
and solvent extraction to extract the valuable metals (Meshram et al.,
2020; Shi et al., 2019). Some hydrometallurgical processes have draw
backs of relatively long leaching time and low leaching efficiency
because of the high valence state of the active cathode material and the
strong binding force of the organic binders (Makuza et al., 2021).
Moreover, the vast consumption of concentrated acid and reductants
(Di et al., 2020; Shi et al., 2019; Zheng et al., 2018) and the multiple
process steps generate significant effluent, which can exacerbate sec
ondary pollution from the discharge of acidic wastewater and gas during
the leaching processes (Makuza et al., 2021). Li is also dispersed
amongst these separation and refining stages, leading to a low lithium
recovery (Di et al., 2020; Lv et al., 2018; Peng et al., 2019). Alterna
tively, pyrometallurgical treatments can be used to extract and purify
metals (Lv et al., 2018). The pyrometallurgical recycling options possess
the advantages of a high rate of chemical reactions, allowing large
treatment capacity (Jie et al., 2020; Ren et al., 2017), being relatively
flexible in the feed material, simple operation, and the dross has negli
gible environmental impacts (Zheng et al., 2018).
It is noteworthy that much emphasis, especially on the industrial
scale, has been placed on the extraction of heavy metals: cobalt and
nickel, because of the high economic value associated with these metals
(Makuza et al., 2021). Dwelling only on the recovery of these heavy
metals has a couple of drawbacks. Firstly, lithium constitutes a signifi
cant proportion of the LIB. The lithium mineral reserves are gradually
depleting; hence there is a need to recover Li from spent LIBs, which is a
meaningful way to secure its availability. Secondly, battery manufac
turers’ transition to less costly cathode material combinations has
adverse impacts on recycling methods that are material-specific, as it
will deem those processes not economically favorable (Sonoc et al.,
2015). Moreover, Li concentration from spent LIBs is also much higher
than that from primary natural ores and brines, and the separation is
much easier to attain than that from the primary resources (Xiao et al.,
2019). The overall Li demand is skyrocketing, and a plausible way to
increase Li production is by enhancing its recovery from recycling spent
LIBs (Chen and Shen, 2017; Di et al., 2020; Kwon and Sohn, 2020)
(Kamran et al., 2021), which is still low using current processing tech
nologies requiring further improvement.
Past researchers have developed novel combined pyro-
hydrometallurgy recycling processes to extract high-value metals from
the spent LIBs and reduce Li loss. Georgi-Maschler et al. (2012) used a
reduction smelting method to recover valuable metals from spent LIBs.
These valuable metals, including Co, Ni, and Mn, were converted to
alloys. Lithium entered the slag or dust fraction during the process
(Georgi-Maschler et al., 2012). Träger et al. (2015) also proposed a
high-temperature process that entailed vacuum and selective carrier gas
evaporation to evaporate Li from the spent LIBs. However, the temper
ature applied during the process was higher than 1400 ◦
C, which inev
itably led to increased energy consumption (Träger et al., 2015).
Considering the shortcoming of the processes mentioned above, Shi
et al. (2019) used sulfation roasting on LiCoO2 cathode material to
produce water-soluble LiSO4 and CoSO4. However, a maximum con
version rate of 44% was achieved even after 240 min of roasting time.
The implication was that CoO was produced during the reaction; hence
it did not serve the purpose (Shi et al., 2019). NaHSO4•H2O has been
used for sulfation roasting; however, this method requires a sizeable
amount of NaHSO4•H2O, leading to high reagent cost and the recovery
effect of Li in the spent LIBs is not clear (Di et al., 2020).
Lately, carbothermic reduction (CTR) roasting has found application
as a pyrometallurgical option for recycling spent LIBs to curb the
excessive high-temperature requirements and loss of Li in the slag dur
ing pyrometallurgical recycling (Makuza et al., 2021). For instance, Li
et al. (2016) and co-workers roasted LiCoO2 and graphite at 1000 ◦
C for
30 min under nitrogen purge gas. The roasting products underwent
water leaching to recover lithium carbonate (Li2CO3), and subsequent
magnetic separation recovered cobalt (Co), and the filter residue was
entirely carbon (C). However, the concentration of the Li-rich solution
was only 337.4 mg/L, making it challenging to recover Li2CO3 and
exacerbate the evaporative crystallization cost, which restricts industrial
application (W. Wang et al., 2019).
In this study, the effect of CTR roasting on the selective extraction of
Li2CO3 using dry grinding followed by carbonated ultrasound-assisted
water leaching (CUAWL) is investigated. Recycling LIBs active cathode
materials using the proposed method can potentially shorten the recy
cling process steps as it eliminates the need to separate the anode and
cathode material in the pretreatment process. The anode and cathode
separation process after automated crushing, which has significantly
dominated the LIB pretreatment process because of its high throughput
(Zhang et al., 2013), has significant technical hurdles due to the great
variation and complexity of the LIB packs, which makes it time-intensive
and intricate (Gaines, 2018; Zhang et al., 2019). The similarity of the
active cathode material and anode material (graphite) in terms of
morphology complicates the separation process further (Kepler et al.,
2015). The proposed method aims to treat a combination of various
types of active cathode material, which represents the actual situation in
industrial LIB recycling plants. Furthermore, the selective recovery of
Li2CO3 results in decreased process steps in separating the roasted
products for regeneration and minimizes the Li losses (Peng et al., 2019).
Direct acid leaching methods have been associated with a low Li2CO3
recovery attributed to the fact that Li losses occur at numerous points
within the complicated LIBs recycling flowsheet from acid leaching
followed by Co, Ni extraction to evaporation and Li2CO3 precipitation
(Peng et al., 2019).
The solubility of Li2CO3 and the recovery of the high-value metals in
the proposed method can be enhanced by grinding, sonication, and
carbonation. Intensive grinding improves the leaching reaction because
of an increased specific surface area, enhanced surface reactivity, and
crystalline structure changes. Since the calcine comprises a significant
amount of graphite, it is susceptible to absorb the lithium ions, inhib
iting the selective recovery of Li2CO3 from the water leaching solution
(Lombardo et al., 2020; Makuza et al., 2021). Yue et al. (2018) also
reported the difficulty of completely separating Co from Li2CO3 and
graphite from sintered agglomeration products using physical methods.
Sonication is adopted to cause ultrasonic cavitation effects in the
leaching solution, which leads to chemical impacts and mechanical ac
tion between solid and liquid interfaces, thereby facilitating desorption
(Jiang et al., 2018; Zhou et al., 2021). The carbonation process involves
injecting CO2(g) into the leaching solution to transform the lowly soluble
Li2CO3 (13.3 g/L at 20 ◦
C (Hu et al., 2017) into more soluble LiHCO3
(55.0 g/L at 20 ◦
C (Yi et al., 2011).
2. Materials and methods
2.1. Materials
This work was conducted on a black mass (mixture of cathode and
anode material) made up of different cathode material combinations
and anode (graphite) of spent lithium-ion batteries provided by a Chi
nese LIB recycling facility. The X-ray diffractogram of the black mass
before roasting is illustrated in Fig. 1, and Figure S1 shows the SEM and
elemental mapping images. The spatial distribution of the metals Ni, Co,
and Mn in the raw material shows that they are positioned in different
particles. Considering these conspicuous features and using XRD con
firmations (Fig. 1), the principal cathode materials in the black mass are
LiCoO2 (LCO), LiMn2O4 (LMO), and LiNiO2 (LNO). Particle size analysis
shows 90% below 34.026 μm, with a major portion in the 9–40 μm range
(Figure S2). The chemical composition of the black mass used in the
experiment is represented in Table 1.
2.2. Experimental
The recycling of the mixture of the anode and various cathode
B. Makuza et al.
3. Resources, Conservation & Recycling 174 (2021) 105784
3
materials (LiCoO2, LiMn2O4, and LiNiO2) by carbothermic reduction
roasting and the method of enhanced selective recovery of Li2CO3 was
studied as follows (as depicted in Fig. 2), and the material balance is
illustrated in Table S1.
The black mass of spent lithium-ion batteries was dried at 110 ◦
C for
6 h in an oven (WGL-125, Taisite). The dried powder was mixed using a
roller mixer (RM100 Miulab, Hangzhou, China) at 80 rpm for 30 min to
obtain a homogeneously mixed powder. After which, a sample of 5 ±
0.005 g was placed in an alumina crucible for each roasting experiment,
as illustrated in Fig. 3.
The alumina crucible with the sample was adjacently attached to the
tip of a K-type thermocouple and placed into a horizontal tube furnace
(OTF-1200X-VF, HF-Kejing, China) on the cool zone. A vacuum pump
(RS-2, Haoyu, China) was then used to remove air from the quartz tube
before purging with Ar gas. Ar gas flow rate was maintained at 300 mL/
min using a mass flow controller (Omega, FMA-A2404), and the heating
rate was 30 ◦
C/min. The temperature was recorded by an HH806W
wireless multi-logger (accuracy of ± 0.05%, Omega, Inc., Norwalk,
USA). After attaining the target temperature, the alumina crucible
containing the sample was slowly pushed into the hot zone using the
thermocouple to prevent air ingress and also minimize the reactions
taking place during heating up. During heating, the cathode powder was
Fig. 1. X-ray diffractogram of an untreated sample containing black mass
(mixture of cathodes and anode materials).
Table 1
Elemental composition of the black mass of spent Li-ion batteries used in this study (wt.%).
Composition C Li Ni Co Mn Al Cu Fe O
Content wt.% 40.90 3.61 2.38 19.80 5.98 1.82 0.95 0.09 Balance
Fig. 2. Flowsheet of carbothermic reduction process of the spent lithium-ion battery black mass and the proposed dry grinding – CUAWL process for selective
extraction of lithium and maximized recovery of the high-value metals by acid leaching. (For interpretation of the references to colour in this figure legend, the reader
is referred to the web version of this article.)
B. Makuza et al.
4. Resources, Conservation & Recycling 174 (2021) 105784
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reduced by the graphitic anode powder present in the mixture. Once the
pre-determined roasting time elapsed, the sample was slowly pulled
back to the cool zone using the thermocouple to allow fast cooling.
Some factors that may influence the reduction roasting experiment
were investigated, such as roasting temperature (500–1000 ◦
C) and
roasting time (15–120 min).
The roasted product was weighed to determine the relative weight
loss, and a sample of 1 ± 0.005 g was leached with ultra-pure water
(UPW) in a water bath (leaching temperature 50 ◦
C, liquid-solid ratio 50
mL/g, magnetic stirring speed 100 rpm, leaching time 3 h). The effect of
grinding (grinding speed 3000 rpm, grinding time 1–10 min), sonication
(ultrasound frequency 40 kHz), and carbonation (CO2 flow rate 25–100
mL/min) on the leaching efficiency of Li were also studied. After water
leaching, the solid residue from water leaching was digested using a
sulphuric acid solution (leaching temperature 80 ◦
C, liquid-solid ratio
20 mL/g, acid concentration 4 M, magnetic stirring speed 100 rpm,
leaching time 3 h). The residue from sulphuric acid leaching was further
digested completely using aqua regia to determine the percentage of
undissolved high-value metals (leaching temperature 95 ◦
C, acid volume
20 mL, magnetic stirring speed 100 rpm, leaching time 4 h).
The leaching efficiency of metals was mainly used to evaluate the
efficiency/performance of the roasting process, and the leaching effi
ciency is calculated as follows;
ηw =
[
Cw Vw
CwVw + CsVs + CaVa
]
× 100% (1)
ηs =
[
Cs Vs
CwVw + CsVs + CaVa
]
× 100% (2)
ηa =
[
CaVa
CwVw + CsVs + CaVa
]
× 100% (3)
where ηw (%), ηs (%) and ηa (%) represents the water, sulphuric acid, and
aqua regia leaching efficiency respectively of element “i”; Cw (g/L), Cs
(g/L), and Ca (g/L) represents the concentration of element “i” in water,
sulphuric acid, and aqua regia leaching solution, respectively, and Vw
(L), Vs (L), and Va (L) represent the volume of leaching solution of
element “i” in water, sulphuric acid, and aqua regia leaching solution,
respectively.
2.3. Measurement and characterization
Simultaneous thermogravimetric analysis and differential thermal
analysis (TG-DTA, HCT-4, Henven, China) were used to investigate the
thermal decomposition behaviors of the black mass at a heating rate of
10 ◦
C/min under an argon atmosphere. For the TG-DTA measurements,
the temperature range was from room temperature to 1500 ◦
C. The
concentrations of the gaseous reduction product CO and CO2 were
continuously measured using a gas analyzer (Gasboard-3000Plus, Cubic-
Ruiyi, China). The concentrations of all metals in the leachate were
determined by inductively coupled plasma-optical emission spectrom
etry (ICP-OES, PerkinElmer’s-Avio 500). The particle size distribution of
powders was performed using a laser diffraction particle size analyzer
(Malvern Mastersizer MS2000) with the Hydro S dispersion unit (ca
pacity 800–900 mL). Reduced products from the experiments were
mounted into epoxy, ground, and polished to observe their elemental
distribution and morphology using a scanning electron microscope
(SEM; TESCAN–Mira3 h, Czech Republic), complemented by an EDS
detector (Oxford X MAX20, UK). Phase identification in the reduced
samples was conducted using an X-ray powder diffractometer (XRD, D/
Max-2500/PC, Rigaku, Japan) using Cu-Kα radiation for their qualita
tive mineralogical composition. X-ray photoelectron spectroscopy (XPS)
analysis was performed using a Thermo Scientific K-Alpha instrument
equipped with Al Kα monochromatized radiation at constant analysis
energy (CAE) of 50 eV to determine the distribution density and binding
energy of the elements in the materials.
3. Results and discussion
3.1. Theoretical feasibility and thermal analysis of carbothermic
reduction
As reported by Mao et al. (2018) and other numerous researchers,
the active cathode material (LiCoO2, LiMn2O4, and LiNiO2) is not
reduced directly by the graphite (Liu et al., 2019; Mao et al., 2018;
Massarotti et al., 2002; Vieceli et al., 2021). Instead, the active cathode
material decomposes first, as depicted by the elementary reactions
(4–6).
(i) Thermal decomposition
4LiCoO2 = 2Li2O + 4CoO + O2(g) (4)
2.4LiMn2O4 = 1.6Mn3O4 + 1.2Li2O + O2(g) (5)
4LiNiO2 = 2Li2O + 4NiO + O2(g) (6)
After thermal decomposition, the resultant metal oxides are reduced by
graphite (anode material), and the possible chemical reactions corre
sponding to the reaction between the thermally decomposed cathode
material and graphite are depicted by reactions (7–14). The standard
Gibbs free energy change (ΔG) of the carbothermic reduction of the
decomposed cathode materials calculated using HSC 6.2 (Roine, 2018)
and the TG-DTA analysis on the decomposition and carbothermic
reduction of the black mass along with the off-gas CO and CO2 analysis is
illustrated in Fig. 4a,b. Thermodynamic computations were only
considered for the CTR reactions of the decomposed cathode material.
The active cathode material decomposition temperatures were taken
from reference works (Massarotti et al., 2002; Toma et al., 2020; Yue
et al., 2018).
(ii) Carbothermic reduction of decomposed cathode material
Fig. 3. Experimental setup for carbothermic
reduction of the black mass. 1. Pressure gauge;
2. Mass flow controller; 3. Valve; 4. Crucible
with the sample; 5. Thermocouple tip attached
to crucible; 6. Thermal insulation block; 7.
Thermocouple handle for pushing and pulling
the sample in the quartz tube; 8. Temperature
data logger; 9. Vacuum inlet; 10. Off gas outlet
to gas analyzer; 11. Gas analyzer off-gas outlet;
12. Off-gas readings; 13. Temperature readings.
(For interpretation of the references to colour in
this figure legend, the reader is referred to the
web version of this article.)
B. Makuza et al.
5. Resources, Conservation & Recycling 174 (2021) 105784
5
2CoO + C = 2Co + CO2(g)ΔGo
= − 0.144T + 36.18 ( − 50.2kJ / mol at 600o
C) (7)
CoO + CO(g) = Co + CO2(g) ΔGo
= 0.0164T − 43.98 ( − 34.1 kJ / mol at 600o
C) (8)
2Mn3O4 + C = 6MnO + CO2(g) ΔGo
= − 0.251T − 0.139 ( − 150.7 kJ / mol at 600o
C) (9)
Mn3O4 + CO(g) = 3MnO + CO2(g) ΔGo
= − 0.0368T − 62.13 ( − 84.2 kJ / mol at 600o
C) (10)
2MnO + C = 2Mn + CO2(g) ΔGo
= − 0.149T + 334.79 (245.4 kJ / mol at 600o
C) (11)
MnO + CO(g) = Mn + CO2(g)ΔGo
= 0.0141T + 105.33 (113.8 kJ / mol at 600o
C) (12)
2NiO + C = 2Ni + CO2(g) ΔGo
= − 0.179T + 31.93 ( − 75.5 kJ / mol at 600o
C) (13)
NiO + CO(g) = Ni + CO2(g) ΔGo
= − 0.0012T − 46.1 ( − 46.8 kJ / mol at 600o
C) (14)
(iii) Oxidation reactions
C + O2(g) = CO2(g) ΔGo
= − 0.0018T − 394.47( − 395.6 kJ / mol at 600o
C) (15)
2C + O2(g) = 2CO(g)ΔGo
= − 0.179T − 270.34 ( − 377.7 kJ / mol at 600o
C) (16)
(iv) Boudouard reaction
C + CO2(g) = 2CO(g) ΔGo
= − 0.177T + 124.13 (17.9 kJ / mol at 600o
C) (17)
Regarding the oxidation reactions of carbon (reactions 15–17), as
envisaged in the thermodynamic calculations (Fig. 4a), reaction (15) is
favored at temperatures lower than 700 ◦
C, whereas reaction (16) is
expected to dominate at 700 ◦
C and above, which aligns with the TG-
DTA result (Fig. 4b) as significant CO(g) evolution occurred from 700
◦
C onwards.
Roasting is essential to facilitate the carbothermic reduction of the
decomposed cathode material as the ΔG values of reactions (7), (9–11),
and (13) become more negative with increasing temperature. The
resultant metal oxides from the decomposition of the active cathode
material can be reduced by C and CO(g). NiO and CoO can be fully
reduced by C and CO(g) to form Ni and Co respectively, Mn3O4 is reduced
to form MnO, which cannot be reduced further to Mn within the tem
perature range plotted, and the decomposition product Li2O reacts with
CO2(g) to form Li2CO3. However, reaction (18) shows an increase in ΔG
with increasing temperature, which implies that increasing the roasting
temperature further might not benefit the generation of Li2CO3 and
above 962 ◦
C, the formed Li2CO3 can be reduced by graphite forming
Li2O (reaction 19).
(v) Formation of lithium carbonate
Li2O + CO2(g) = Li2CO3 ΔGo
= 0.134T − 174.80 ( − 94.4 kJ / mol at 600o
C) (18)
(vi) Carbothermic reduction of lithium carbonate
Li2CO3 + C = Li2O + 2CO(g) ΔGo
= − 0.311T + 299 (112.4 kJ / mol at 600o
C) (19)
The decomposition profile and the carbothermic reduction of the
decomposed cathode material can be split into 3 distinct regions
(Fig. 4b). There is no mass loss in Region I, and the off-gas results show
no traces of gas evolution. Mass loss started in Region II at around 190
◦
C, resulting in the evolution of CO2. As reported by Toma et al. (2020),
the decomposition of LiNiO2 starts around 200–220 ◦
C (reaction 6),
generating O2 gas. Thus the CO2 evolution around 190 ◦
C (Fig. 4b) is
presumably from the oxidation of graphite by O2 gas generated from
reaction 6. The total absence of mass loss in the TG-DTA results by Yue
et al. (2018) depicted that LiCoO2 material was not decomposed at a
temperature below 650 ◦
C. According to Massarotti et al. (2002), the
decomposition of LiMn2O4 commences around 600 ◦
C, and the decom
position product after 800 ◦
C is reduced completely into Mn3O4 and
MnO. Thus the mass loss in the temperature range of 600–900 ◦
C and its
corresponding CO and CO2 evolution are likely associated with the
decomposition of LiCoO2 and LiMn2O4 (reactions 4 and 5) and subse
quent oxidation of graphite by the resultant O2 gas (reactions 15 and
Fig. 4. a) Plot of the relationship between ΔG◦
(kJ/mol) and temperature ( ◦
C) for reactions (7–19), b) TG-DTA analysis of the mixture of the anode and cathode
material (Heating rate = 10 ◦
C/min; Argon flow rate = 50 mL/min).
B. Makuza et al.
6. Resources, Conservation & Recycling 174 (2021) 105784
6
16). The endothermic peak at 830 ◦
C is a significant carbothermic
reduction process as it takes place simultaneously with the highest in
tensity of CO(g) evolution and abrupt mass loss (6.64%). Based on the
analysis, the influence of carbothermic reduction roasting temperature
in the range of 500–1000 ◦
C was investigated, aiming to attain
maximum selective recovery of Li2CO3.
3.2. Effect of roasting temperature
The effect of roasting temperature on the leaching efficiency of Li, Ni,
Mn, Co, Cu, Al, and Fe was investigated under the following roasting
conditions: roasting temperature of 500− 1000 ◦
C at 100 ◦
C intervals
and 60 min roasting time. The temperature profile during the roasting
process and the corresponding CO and CO2 concentrations in the off-gas,
the particle size distribution, and the x-ray diffractogram of the roasted
product for the range 500–1000 ◦
C are illustrated in Fig. 5a-d.
The temperature profile illustrates that the fast heating and the rapid
cooling mechanism was achieved (Fig. 5a) and, intense CO2 and CO
peaks appeared shortly after the target temperature was reached
(Fig. 5b). The peaks were attributed to the interaction of the thermally
decomposed cathode material with graphite, represented by Eqs. (7-
17). At 700 ◦
C and 800 ◦
C, the CO peaks show a surge, which could
result from multiple consecutive and parallel reactions coinciding. CO2
is the most dominant gas product at temperatures below 800 ◦
C, as seen
in Fig. 5b, and it also conforms with the thermodynamic computation
and TG-DTA result (Fig. 4b). Thus, stronger reducing conditions are
produced at higher reaction temperatures, while lower temperatures
result in less reducing conditions and slower kinetics (Barker et al.,
2003).
With increasing roasting temperature, the particle size increased
attributed to particle agglomeration (Fig. 5c and Figure S3) (Chen et al.,
2010). For instance, the particle size distribution (PSD) shows 50%
passing 14.845 µm after CTR at 600 ◦
C (Figure S3b), and it rises to
23.341 µm after CTR at 1000 ◦
C for 60 min (Figure S3f), which proves
particle agglomeration. Since there is more reduction with increasing
temperature, at lower temperatures, we are prone to attain metal oxides,
and at high temperatures, we obtain alloy(s) as depicted by the transi
tion from metal oxide to metallic form in Figure S4a-f. Moreover, the
different distribution of elements before and after roasting shows that
the heavy metals in the untreated cathode material were transformed to
alloy form with increasing temperature, as illustrated in Figure S4a-f.
The heavy metals distribution after reduction roasting transitioned from
random distribution (Figure S1) to a uniform distribution (Figure S4),
which confirms the transition from lithiated metal oxide to alloy as
depicted by the positioning of the metals in the same region
(Figure S4a-f).
Fig. 5. Carbothermic reduction roasting of the black mass for the temperature range 500–1000 ◦
C for 60 min: a) temperature profile, b) the corresponding CO(g) and
CO2(g) concentration in the off-gas, c) particle size distribution, and d) X-ray diffractogram and corresponding mass loss change at each temperature: d1) 500 ◦
C, d2)
600 ◦
C, d3) 700 ◦
C, d4) 800 ◦
C, d5) 900 ◦
C, and d6) 1000 ◦
C. (For interpretation of the references to colour in this figure legend, the reader is referred to the web
version of this article.)
B. Makuza et al.
7. Resources, Conservation & Recycling 174 (2021) 105784
7
According to Fig. 5d, the roasting temperature significantly in
fluences the weight loss of the roasted material (Liu et al., 2019). The
differences in the weight loss (Δwt%) of the roasted samples depict that
the weight loss increases with increasing roasting temperature. At 1000
◦
C, there is a weight loss of approximately 30%, almost triple the weight
loss at 500 ◦
C. The cumulative CO formation with increasing roasting
temperature reduced the decomposed metal oxides further, which also
contributed to increased weight loss with increasing roasting tempera
ture (Fig. 5d). The off-gas peaks are gradually getting broader with
increasing temperature, and this corresponds to the increasing weight
loss with increasing temperature illustrated in Fig. 5d.
The XRD peaks of the active cathode material before roasting are
indexed to be LiCoO2, LiMn2O4, and LiNiO2 (Fig. 1), and they disappear
after reduction roasting in the temperature range 500− 1000 ◦
C. Instead,
some diffraction peaks of Li2CO3, Ni, Co, CoO, and MnO are observed
(Fig. 5d). These significant phases of the cathode materials observed
after reduction roasting are consistent with the XRD analysis results by
Liu et al. (2019) and Lombardo et al. (2019). The results depict that
lower temperatures were associated with less reduction as significant
CoO peaks were observed at 500 ◦
C and 600 ◦
C. At 600 ◦
C, the CoO
peaks gradually reduced and finally disappeared afterward. The XRD
peak intensity for graphite in the roasted mixture is relatively large, and
this was expected because of the excessive amount of graphite present in
the mixture; hence, the graphite would not be wholly consumed. How
ever, the high graphite content in the reduced product is susceptible to
deter maximum selective extraction of Li2CO3 as it gets absorbed by the
graphite (Lombardo et al., 2020; Makuza et al., 2021).
Fig. 6a,b shows the water leaching efficiency of Li and acid leaching
efficiency of the target metals after roasting. The leaching efficiency in
the temperature range of 500–1000 ◦
C remained above 77% (Fig. 6a)
because the active cathode material had been entirely decomposed, as
seen from the absence of peaks ascribed to the cathode material in the
XRD patterns (Fig. 5d).
Maximum recovery of Li (84.08% Li) was attained at 600 ◦
C, after
which a steady and slow decrease in the leaching efficiency with
increasing roasting temperature was observed. By utilizing thermody
namic calculations (reaction 18), higher roasting temperatures deter
the formation of Li2CO3, which is augmented by the decrease in the
Li2CO3 peaks with increasing roasting temperature and ultimately the
absence of Li2CO3 peaks at 900 ◦
C and 1000 ◦
C (Fig. 5d). At 400 ◦
C, the
Li leaching efficiency was a mere 30% because the active cathode ma
terial had not been wholly decomposed, clarified by the presence of
peaks ascribed to LiCoO2 and LiMn2O4 in the XRD pattern (Figure S5).
On the contrary, higher roasting temperatures have adverse effects
on the extent of sulphuric acid dissolution reactions (Liu et al., 2019).
Fig. 6b shows that an increase in the roasting temperature deters the
acid leaching efficiency of the target metals significantly. The acid
leaching efficiency of the high-value metals was greater than 99% at 500
◦
C but dropped sharply with a continuous increase in the roasting
temperature (Fig. 6b). For instance, the acid leaching efficiency of the
high-value metals Ni, Co, and Mn dropped to 19.98%, 45.76%, and
96.56%, respectively, after roasting at 800 ◦
C and further dropped to
18.33%, 25.98%, and 24.10%, respectively after roasting at 1000 ◦
C.
The drop in the leaching efficiency of the target metals can be partially
attributed to calcine agglomeration with increasing temperature
(Fig. 5c) (Chen et al., 2010). Furthermore, the transition to alloy form is
possibly another important reason for the drop in the leaching efficiency
(Figure S4).
Considering energy conservation, enhanced selective recovery of
Li2CO3, and the maximized recovery of the high-value metals (Fig. 6),
the optimum roasting temperature was fixed at 600 ◦
C for the following
experiments.
3.3. Development of dry grinding and CUAWL process for enhanced
recovery of high-value metals
The roasted product was ground for 1 min at 3000 rpm and subjected
to ultrasonic-assisted water leaching under a continuous bubbling of
carbon dioxide gas to investigate the influence of dry grinding and
CUAWL method on the selective recovery of Li and the maximized acid
recovery of the high-value metals. The results are shown in Fig. 7.
The water leaching efficiency of Li in the absence of dry grinding and
CUAWL was 84.08%, and it increased to 85.60% after grinding for 1 min
at 3000 rpm. The combination of grinding and sonication further
increased the Li leaching efficiency to 87.14%. A positive effect was also
noted from the combination of grinding, sonication, and carbonation as
the leaching efficiency further increased to 89.13% under the same
leaching conditions.
In order to further analyze the products of carbothermic reduction
roasting and dry grinding - CUAWL, XPS analysis was performed on the
roasted black mass before and after dry grinding - CUAWL (Fig. 8).
Fig. 8a-f shows the appearance of relevant peaks corresponding to
Li2CO3, Ni, MnO, CoO, and graphite. The C 1 s spectrum before dry
grinding - CUAWL showed peaks at 283.90 eV and 288.63 eV. The
283.90 eV peak was attributed to graphite present in the mixture, and
the 288.63 eV peak was Li2CO3. There are only two peaks of O 1 s, which
are 528.98 eV and 531.36 eV, respectively. By utilizing confirmations by
Verdier et al. (2007), we can ascertain that the peak near 531.36 eV
corresponds to Li2CO3, and the peak near 528.98 eV is the characteristic
peak of metal oxide, resulting from the reduced active cathode
Fig. 6. Leaching efficiency of the black mass roasted at 500–1000 ◦
C for 60 min: a) water leaching efficiency of the roasted black mass in the absence of dry grinding
- CUAWL as a function of the roasting temperature, b) acid leaching efficiency of the metals in the water leaching residue (leaching temperature 80 ◦
C, acid
concentration 4 M, leaching time 3 h).
B. Makuza et al.
8. Resources, Conservation & Recycling 174 (2021) 105784
8
materials. After dry grinding and CUAWL, the peak shape of the Li 1 s
(54.93 eV) became narrow (peak area reduced to about 25%), and the
peak intensity became much weaker, which shows that the majority of Li
had been leached out. The detectable O–C bond in C 1 s (~285 eV) after
dry grinding and CUAWL is attributed to adventitious carbon contami
nation from grinding and exposure to the atmosphere.
The Co 2p core peak before dry grinding and CUAWL is divided into
Co 2p1/2 and Co 2p3/2 as the split spin-orbit components (Δmetal =
16.68 eV), each of which has a satellite peak. In the Co2p spectra,
802.36 eV, 795.79 eV, 784.32 eV, 779.93 eV correspond to the average
oxidation states of Co2+
observable from the apparent satellite features
and 778.20 eV represents cobalt. The CoO had not been completely
reduced as there was still a vast amount of Co2+
. The Mn 2p core peak is
divided into Mn 2p1/2, and Mn 2p3/2 as the split spin-orbit components
(Δmetal=11.16 eV), and it has a satellite peak (~647 eV) that is not
present for either Mn2O3 or MnO2, and thus it should represent MnO.
The Ni 2p3/2 peak (852.6 eV) is attributed to metallic nickel, and the Ni
2p peaks of the reduced LiNiO2 after dry grinding and CUAWL has a
complex structure that is a combination of core-level and satellite
features.
The XPS spectra of Ni 2p, Mn 2p, Co 2p, and O 1 s after dry grinding
and CUAWL increase in peak width and reveal a shift in their peak po
sitions towards the higher binding energy side attributed to a decrease in
particle size after grinding. This effect is well known in XPS, giving rise
to size-dependent binding energy (BE) shifts relative to the BE for bulk
metal. The binding energy of core orbitals is strongly size-dependent due
to size effects on screening and relaxation in the XPS core-hole final state
(Dai et al., 2017).
3.3.1. Effect of roasting time
The effect of roasting time on the leaching efficiency of Li, Ni, Mn,
Co, Cu, Al, and Fe was investigated under the following roasting con
ditions: roasting time of 15–120 min and roasting temperature of 600 ◦
C.
Fig. 9a-d shows the water leaching efficiency of Li, the acid leaching
efficiency of the target metals, CO and CO2 off-gas concentrations during
CTR, and the x-ray diffractogram of the roasted product.
The Li water leaching efficiency gradually decreased with an in
crease in roasting time. As observed in Fig. 9a, the maximum recovery of
Li (91.68% Li) could be attained after 15 min of roasting, which implies
that the CTR rate was rapid. With the holding time increased to 30 min,
the lithium leaching efficiency was stagnated at 91.66%. A continuous
increase in the holding time to 60 and 120 min resulted in a further
decrease in Li leaching efficiency to 89.14%.
A decrease in the acid leaching efficiency of the high-value metals
with prolonged roasting time was also observed in Fig. 9b, which could
be attributed to the resultant formation of metallic phases after CTR. An
increase in particle size with prolonged heating was also noted as the
particle size analysis shows 50% passing 14.731 µm after roasting for 30
min (Figure S6a), and it rose to 14.845 µm after roasting for 60 min
(Figure S3b). The CO2 and CO peaks were alike (roughly 5.25% CO2 and
1.25% CO) for 15, 30, 60, and 120 min of roasting (Fig. 9c), contributing
Fig. 7. The effect of grinding, sonication, and carbonation on the selective
recovery of lithium (roasting temperature = 600 ◦
C, roasting time = 60 min,
grinding time = 1 min, grinding speed = 3000 rpm, leaching time = 3 h, CO2
flow rate = 100 mL/min, ultrasound frequency = 40 kHz).
Fig. 8. XPS spectra of a) Li 1 s, b) C 1 s, c) O 1 s, d) Ni 2p, e) Mn 2p, and f) Co 2p core peaks of the black mass after roasting and after dry grinding - CUAWL (roasting
temperature = 600 ◦
C, roasting time = 60 min, grinding time = 1 min, grinding speed = 3000 rpm, leaching time = 3 h, CO2 flow rate = 100 mL/min).
B. Makuza et al.
9. Resources, Conservation & Recycling 174 (2021) 105784
9
to the insignificant weight loss change (Δwt%) and microstructural
changes with prolonged roasting time (Fig. 9d).
Considering energy conservation, enhanced selective recovery of
Li2CO3, and the maximized recovery of the high-value metals (Fig. 9),
the optimum roasting time was fixed at 30 min for the following
experiments.
3.3.2. Effect of leaching duration
The effect of dry grinding and CUAWL time on the leaching effi
ciency of Li is illustrated in Fig. 10, which shows that dry grinding and
CUAWL improved the leaching efficiency of Li, especially in the initial
stages.
A rapid recovery rate of Li was observed within the first 30 min of the
leaching process, with 85.59% of Li being leached within the first 30
min, which is higher than the Li recovery achieved after 3 h in the
absence of dry grinding and CUAWL. After that, the recovery rate of Li
increases steadily. The faster leaching rate for dry grinding and CUAWL
could be attributed to the reduced particle size, ultrasonic cavitation,
and enhanced Li2CO3 solubility.
3.3.3. Effect of milling
The effect of milling on the water leaching efficiency of Li and the
recovery rate of high-value metals is illustrated in Fig. 11a-c.
An increase in the leaching efficiency with decreasing particle size
Fig. 9. Analysis of the black mass after roasting at 600 ◦
C for 15–120 min: a) dry grinding and CUAWL efficiency as a function of the roasting time (grinding time =
1 min, grinding speed = 3000 rpm, CO2 flow rate = 100 mL/min, ultrasound frequency= 40 kHz), b) acid leaching efficiency of metals in the water leaching residue
(leaching temperature 80 ◦
C, acid concentration 4 M, leaching time 3 h), c) corresponding CO and CO2 off-gas concentrations during roasting and d) X-ray dif
fractogram and weight loss after roasting: d1)15, d2) 30, d3) 60, and d4)120 min.
Fig. 10. Effect of leaching duration on the selective recovery of lithium by dry
grinding and CUAWL (roasting temperature = 600 ◦
C, roasting time = 60 min,
grinding time = 1 min, grinding speed = 3000 rpm, CO2 flow rate = 100 mL/
min, ultrasound frequency = 40 kHz).
B. Makuza et al.
10. Resources, Conservation & Recycling 174 (2021) 105784
10
was observed, which conforms with the theory (TaysserLashen et al.,
2016). Before grinding, the particle size distribution was 50% passing
14.8 µm, and dropped to 14.1 µm and ultimately 13.4 µm after 1 and 2.5
min of grinding, respectively (Figure S6a-c). The Li water leaching ef
ficiency increased accordingly from 88.91% before grinding to 91.68%,
92.25%, and 92.60% after 1, 2.5, and 10 min of grinding, respectively
(Fig. 11a). As the metal particle size decreased, the total surface area of
particles and the active spots of the reaction increased, which sped up
the reaction. However, after 10 min of grinding, the particle size dis
tribution increased to 50% passing 18.3 µm (Figure S6d), attributed to
strong inter-particle aggregation promoted by intensive grinding
(negative milling)(Guzzo et al., 2015). A similar aggregation
phenomenon has been reported during the synthesis of LiFePO4 cathode
material after prolonged milling time (Zhang et al., 2010).
The positive effect of grinding on the recovery of high-value metals
could be further extended to the black mass roasted at 1000 ◦
C. Before
grinding, the roasted material had limited solubility in sulphuric acid.
However, after grinding for 1 and 2.5 min, the particle size decreased
from 23.3 µm before grinding to 16.1 µm and 14.8 µm respectively, after
grinding (Figure S7a-c). The leaching efficiency of the high-value
metals increased sharply after l minute of grinding and progressed
with a steady increase from 2.5 min onwards (Fig. 11c). The leaching
efficiency of Mn, Ni, and Co increased from 24.10%, 18.33%, and
25.98% before grinding to 75.53%, 56.22%, and 80.68% after 10 min of
grinding at 3000 rpm, respectively. Since grinding is an energy-intensive
process, especially for extremely fine material (used in this study),
therefore, 2.5 min was chosen as the optimum grinding time for further
experiments.
3.3.4. Effect of water leaching temperature
The effect of water leaching temperature on the leaching efficiency
of Li and target metals is illustrated in Fig. 12a,b. Fig. 12a shows that
high temperatures are more favorable for the dissolution of Li2CO3 in the
water leaching solution because of the increased kinetics. A maximum
recovery of Li (92.25% Li) was attained at 50 ◦
C, and the Li recovery rate
gradually decreased with a decrease in leaching temperature up to a
recovery rate of 85.54% at 20 ◦
C (Fig. 12a).
The solubility of CO2(g) in water increases with a decrease in tem
perature (Wiebe and Gaddy, 1940), and Eqs. (20-23) illustrate the
carbonation mechanism.
CO2(g) + H2O = CO2(aq) + H2O (20)
CO2(aq) + H2O = H2CO3 (21)
Li2CO3 + H2CO3 = 2LiHCO3 (22)
H2CO3⇄ HCO−
3 + H+
⇄CO2−
3 + 2H+
(23)
When the temperature was lowered from 50 ◦
C, the concentration of
CO2(aq) increased, forcing reaction 23 to the right, which lowered the
pH of the water leaching solution and ultimately led to the dissolution of
heavy metals (Fig. 12a). The recovery of heavy metals in the water
leaching solution leached at 50 ◦
C was minimum, and a gradual increase
was observed with a continuous decrease in leaching temperature. At 50
◦
C the leaching efficiencies for Ni, Mn, Co, Cu, Al, and Fe was 0.43%,
0.52%, 0.49%, 0.04%, 0.11%, and 0.29%, respectively, and it increased
to 1.43%, 6.61%, 0.87%, 13.95%, 11.07%, and 3.39%, respectively,
after water leaching at 20 ◦
C which showed the negative effect of lower
leaching temperatures on the selective recovery of Li2CO3 (Fig. 12a). By
fixing the water leaching temperature at 50 ◦
C, high purity Li2CO3 could
be obtained.
3.3.5. Effect of CO2 flow rate
The effect of CO2 flow rate on the leaching efficiency of Li and re
covery of target metals is illustrated in Fig. 13a,b. As shown in Fig. 13a,
the increase of the CO2 flow rate enhanced the dissolution of Li2CO3. The
increase in the leaching efficiency with increasing CO2 flow rate could
be attributed to the increase of the volumetric mass transfer coefficient
of the liquid to solid phases (Wang and Hu, 2020; Yi et al., 2011). The
recovery efficiency of the high-value metals hardly shows any change, as
the CO2(g) flow rate does not affect the leaching efficiency, given that
water leaching temperature is fixed above 50 ◦
C (Fig. 13b).
3.3.6. Further separation and refining
After dry grinding and CUAWL, the recovered filtrate was subjected
to evaporative crystallization at 95 ◦
C to obtain Li2CO3. High-purity
Li2CO3 was attained (99.2%) without any prior purification process,
Fig. 11. Effect of milling time on the: a) selective recovery of lithium by dry
grinding and CUAWL (roasting temperature = 600 ◦
C, roasting time = 30 min,
grinding speed = 3000 rpm, CO2 flow rate = 100 mL/min, ultrasound fre
quency = 40 kHz, leaching time = 3 h), b) acid leaching efficiency of metals in
the water leaching residue for the black mass roasted at 600 ◦
C and, c) acid
leaching efficiency of metals in the water leaching residue for the black mass
roasted at 1000 ◦
C (leaching temperature 80 ◦
C, acid concentration 4 M,
leaching time 3 h).
B. Makuza et al.
11. Resources, Conservation & Recycling 174 (2021) 105784
11
which was much higher than the other reported methods with a purity of
90.0% (Yang et al., 2016), 93.8% (Torres et al., 2020), and 95% (Guzolu
et al., 2017). Fig. 14 shows the x-ray diffractogram and SEM micrograph
of the recovered Li2CO3 and the acid leaching residue.
The x-ray diffractogram of the Li2CO3 recovered after evaporative
crystallization of the LiHCO3 solution is consistent with the standard
PDF card of Li2CO3 (JCPDS Card No. 22–1141), indicating that the ob
tained Li2CO3 has well-crystallized particles (Yan Wang et al., 2019).
The SEM micrograph shows that the Li2CO3 produced has small particles
with a compact cauliflower-like spherulite morphology made of
plate-like facets. The fine Li2CO3 particle size (about 1–5 µm)(Fig. 14b)
promotes the interfacial reaction during cathode regeneration (Liu et al.,
2014). Furthermore, the spherulite product is favorable for the pro
duction of battery-grade lithium carbonate as it improves the flowability
and compressibility of the Li2CO3 product (Yang et al., 2019), and such
spherical and uniform morphology when retained in the cathode ma
terial after regeneration results in promising electrochemical property
(Sa and Sisson, 2015).
The high-value metals remaining in the water leaching residue were
recovered by sulphuric acid leaching (leaching temperature 80 ◦
C, acid
concentration 4 M, leaching time 3 h). The as-obtained filtrate is rich in
high-value metals (Ni 1.93 g/L, Co 14.9 g/L, Mn 4.29 g/L), and it can be
further treated using separation technologies such as precipitation
(Dutta et al., 2018), solvent extraction, and ion exchange (Nguyen and
Lee, 2018) according to the preferred cathode material regeneration
method (Makuza et al., 2021). According to Fig. 14c, the x-ray dif
fractogram of the acid leaching residue shows the absence of peaks
attributed to metal oxides. Instead, a major graphite characteristic peak
at 2θ = 26.4◦
is observed and perfectly matches the graphite pattern
(JCPDS No. 41–1487). SEM image shows that the graphite particles have
an irregularly shaped micrometer size flake-like morphology with a
smooth surface. The EDS results depict that most metals were digested
and contain a scanty amount of trace metal elements (Ni 0.04%, Co
0.05%, Mn 0.00%, Al 0.75%, Cu 0.05%, and Fe 0.05%). The market for
recycled graphite material has expanded, and this graphite residue can
be recycled back into products such as brake linings and thermal insu
lation (U.S. Geological Survey, 2019).
4. Conclusions
This paper proposed a rationale for the controllable carbothermic
reduction method for enhanced selective recovery of Li2CO3 and maxi
mized acid recovery of high-value metals. The developed method in
corporates carbothermic reduction roasting, dry grinding - carbonated
ultrasound-assisted water leaching (CUAWL), and sulfuric acid leaching.
1 The microstructural analysis results depict that the black mass
(mixture of anode and cathode materials) after roasting under opti
mum conditions of 600 ◦
C for 30 min was primarily transformed into
Li2CO3, Ni, Co, CoO, and MnO.
Fig. 12. Effect of leaching temperature on the a) selective recovery of lithium by dry grinding and CUAWL (roasting temperature = 600 ◦
C, roasting time = 30 min,
grinding time = 2.5 min, CO2 flow rate = 100 mL/min, ultrasound frequency = 40 kHz, leaching time = 3 h), b) acid leaching efficiency of the metals in the water
leaching residue (leaching temperature 80 ◦
C, acid concentration 4 M, leaching time 3 h).
Fig. 13. Effect of CO2 flow rate on the a) selective recovery of lithium by dry grinding and CUAWL (roasting temperature = 600 ◦
C, roasting time = 30 min, grinding
time = 10 min, grinding speed =1800 rpm, ultrasound frequency= 40 kHz, leaching time = 3 h), b) acid leaching efficiency of the metals in the water leaching
residue (leaching temperature 80 ◦
C, acid concentration 4 M, leaching time 3 h).
B. Makuza et al.
12. Resources, Conservation & Recycling 174 (2021) 105784
12
2 High-speed grinding enhanced the selective recovery of Li2CO3 and
maximized the acid recovery of high-value metals.
3 The ultrasonic cavitation effects induced by sonication (frequency
40 kHz) enhanced the Li leaching efficiency attributed to the
chemical impacts and mechanical action between solid and liquid
interfaces, thereby facilitating desorption and separation of the
roasted products.
4 Carbonation transformed the lowly soluble Li2CO3 into more soluble
LiHCO3 (CO2 flow rate 100 mL/min, leaching time 3 h, leaching
temperature 50 ◦
C). The recovered leach solution (LiHCO3) is sub
jected to evaporative crystallization to attain high-purity Li2CO3
(99.2%). Subsequently, the water-leached residue was digested by 4
M H2SO4 at 80 ◦
C for 3 h. The optimized experimental results ach
ieved improved leaching efficiencies of up to 92.25% Li, and over
99% of the high-value metals Ni, Mn, and Co could be leached out
from the reduced active cathode materials without adding reductant.
The developed method demonstrated its flexibility in recycling spent
lithium-ion batteries as it was performed on a black mass of various
cathode material combinations (LiCoO2, LiMn2O4, and LiNiO2) and
anode material which is representative of the actual situation in the
industrial recycling facilities. Furthermore, the dry grinding and CUAWL
process is a self-sustaining, environmentally benign process that does
not require external additives.
CRediT authorship contribution statement
Brian Makuza: Investigation, Methodology, Software, Writing –
original draft. Dawei Yu: Conceptualization, Methodology, Resources,
Writing – review & editing, Supervision, Funding acquisition. Zhu
Huang: Visualization, Investigation. Qinghua Tian: Supervision,
Funding acquisition. Xueyi Guo: Supervision, Funding acquisition.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgments
This research was funded by the National Natural Science Founda
tion of China (Grant 51904350, 51922108, and 51874371), Hunan key
research and development program (Grant 2020SK2005), and the
Hunan Natural Science Foundation (Grant 2019JJ20031).
Supplementary materials
Supplementary material associated with this article can be found, in
the online version, at doi:10.1016/j.resconrec.2021.105784.
Fig. 14. a) X-ray diffractogram and b) SEM micrograph of the recovered Li2CO3 (roasting temperature = 600 ◦
C, roasting time = 30 min, grinding time = 2.5 min,
CO2 flow rate = 100 mL/min, ultrasound frequency = 40 kHz, leaching time = 3 h, evaporative crystallization temperature 95 ◦
C); c) X-ray diffractogram and d) SEM
micrograph of the acid leaching residue (leaching temperature 80 ◦
C, acid concentration 4 M, leaching time 3 h). (For interpretation of the references to colour in this
figure legend, the reader is referred to the web version of this article.)
B. Makuza et al.
13. Resources, Conservation & Recycling 174 (2021) 105784
13
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