ACS Symposium: Findings and Opportunities from the 2012 NSF SusCheM Workshop
Ensuring the Sustainability of Critical Materials and Alternatives: Addressing the Fundamental Challenges in Separation Science and Engineering 244th ACS National Meeting, Philadelphia, August 21, 2012 Findings and opportunities fromthe 2012 NSF SusChEM workshop Chair: Susannah ScottDepartment of Chemistry & Biochemistry; Department of Chemical Engineering University of California, Santa Barbara Co-chair: Jim McGuffin-Cawley Department of Materials Science and Engineering Case Western Reserve University Disclaimer: The views herein represent the author’s, and are not necessarily those of the NSF.
SusChEM Sustainable Chemistry, Engineering, and Materials• Systems-level thinking is required: “There are no sustainable parts of unsustainable wholes.” Franzi Poldy, CSIRO• More fundamental research should be use-inspired.• Green is not synonymous with sustainable.• Efficiency is necessary but not sufficient, due to the rebound effect• Sustainability research and education is multidisciplinary and collaborative.
Workshop topics• Discovering new chemistry and materials that will replace rare, expensive and/or toxic chemicals with earth-abundant, inexpensive and benign minerals and chemicals,• Discovering new processes to economically recycle chemicals and materials that cannot easily be replaced, such as phosphorus and the REE’s,• Discovering new chemistry to convert non-petroleum based sources of organics to feedstock chemicals,• Discovering new environmentally-friendly chemical reactions and material processes that use less energy, water, and organic solvents than current practice,• Incorporate sustainability into the curriculum; have earth, physical and social scientists and engineers take common courses; and promote entrepreneurship.
Many separations-relevant issues• Mineral processing and element recycling (including urban mining) – Rare earths – Precious metals – Phosphorus• Chemical process intensification – Integrated reaction/separation in microflow reactors – Improved separation designs in conventional chemical processing• Membranes – Scaleable polymer-inorganic composites – Highly selective metal-organic frameworks (MOFs)/porous coordination polymers (PCPs)• Simplifying complex product streams from biomass-derived sources
Uses of rare earths Light rare earths (LREEs) Heavy rare earths (LREEs) LREEs HREEs catalysts catalysts Ce Nd La Pr X. Du, T. E. Graedel, “Global In-Use Stocks of the RareEarth Elements: A First Estimate”, Environ. Sci. Technol., 2011, 45, 4096. Dy Y Gd Sm Tb Eu
Concentration of supply "There is oil in the Middle East; there is rare earth in China…" Deng Xiaoping, 1992 China now produces almost all of the world’s supply of REEs. Light REEs: from Bastnäsite-containing ores in Inner Mongolia Heavy REEs: adsorbed on laterites (clays) in Southern ChinaX. Du, T. E. Graedel, “Global In-Use Stocks of the Rare Earth Elements: A First Estimate”, Environ. Sci. Technol., 2011, 45, 4096.
Environmental and social costs Bayan Obo LREE open pit mine, Acid tanks and run-off ponds at HREE mining Baotou, Inner Mongolia, China facility near Ganzhou, Jiangxi Province, ChinaEach ton of rare metals mined releases:• 10 – 12 x 103 m3 of waste gas (dust, HF, SO2, H2SO4);• 75 m3 acidic wastewater;• 1 ton radioactive waste residue (Chinese Society of Rare Earths) Photos by Adam Dean. The Telegraph, 19 March, 2011.
“Green” technologies A Toyota Prius contains 30 kg RE: NiMH battery (La, Ce) electric motor/generator (Nd, Pr, Dy, Tb) LCD screen (Eu, Ce)A single compactfluorescent lightbulbcontains 1.5 g RE:phosphor (principally Eu,with smaller quantities of A 3 MW wind turbine contains 600 kg RE:La, Dy, Ce, Pr and Gd) permanent magnets (Nd, Pr, Dy, Tb)
Rare earth export quotas • In 2010, China cut REE export quotas dramatically. • In late 2012, China announced separate export quotas for LREEs and HREEs. Prices in US $/kg, FOB ChinaChinese export quotas, kT REO 2009 2010 2011 8/2012 La 5 22 104 20 Ce 4 22 102 21 Nd 19 50 234 105 Pr 18 48 197 110 Sa 3 14 103 70 www.bloomberg.com Dy 116 232 1450 950 Eu 493 560 2843 2020 Tb 362 558 2334 2000China’s rationales: http://www.lynascorp.com• Rare earths are strategic resources.• Manufacturing high value finished products is preferred over export as low value raw materials.• Need to consolidate and regulate REE production, to better control pollution.
Solvent extractionMixer-settlers used for continuous, counter-current liquid-liquid extraction of RE ions, in ademonstration plant in Australia. Ln3+ ions partition into a non-polar organic solvent containing a ligand such as R2P(O)OH or R3PO. About 600 mixer-settler boxes are required for an integrated separation facility, due to low per- stage efficiency (typically, < 3). R. Wormsbecher, Grace
Rare earth recoveryRecycling of REEs is almost non-existent, due to the high cost of separation.“Distribution entropy” affects recovery prospects:• Nd has a high distribution entropy. – Hard drives, DC motors, permanent magnets, headphones• La has a lower distribution entropy. – Metal hydride battery cathodes, hybrid cars, fluid catalytic cracking (FCC) catalyst • Active component in FCC catalyst is La- exchanged USY • An FCC unit processing 75,000 barrels/day contains 56,000 tons catalyst with ca. 1,000 tons RE • Catalyst lifetime is ca. 1 month • World consumption is ca. 2,300 tons catalyst/day (10% of all RE use) • Spent catalyst contaminated with other metals (Ni, V) is landfilled or used for construction aggregate R. Wormsbecher, Grace
Challenges for RE separation and recoveryAim to reduce energy-, water- and chemical-intensity.Make recycling economically viable.1. Design new chelating agents for highly selective solvent extraction Peterman et al., Separ. Sci. Technol. 2010, 45, 17112. Replace low efficiency mixer-settlers by high efficiency centrifugal contactors3. Explore new solvent systems (e.g., RTIL, scf)4. Develop high affinity ion-exchange resins5. Develop rare earth-selective membranes E. Peterson, Idaho National Lab R. Wormsbecher, Grace
Global food security Sir William Crookes Guano mining in the Central Chincha Islands (Peru), mid-19th centurywarned of impending global famine in address to the British Acad. Sciences (1898) The Atacama Desert (Chile), with the Andes visible inthe background. The remains of a nitrate plant (late 19th century) and its tailings pile can be seen in the middle. P. Marr, “Ghosts of the Atacama: The abandonment of nitrate mining inthe Tarapacá region of Chile”, Middle States Geographer, 2007, 40, 22.
The N-revolutionFritz Haber Alwin Mittasch Carl Bosch J. W. Erisman, M. A. Sutton, J. Galloway, Z. Klimont, W. Winiwarter, “How a century of ammonia synthesis changed the world”, Nature GeoSci. 2008, 1, 636.
Phosphorus in agriculture There is no P-analog of the Haber-Bosch process. “There are no substitutes for phosphorus in agriculture.” USGSLarge pile of bison skulls to be ground into fertilizer, Brazilian corn plants grown on P-treated soil areca. 1870. much taller than control plants like those in the foreground, which did not receive adequatePhoto courtesy of Burton Historical Collection, Detroit Public Library. additional phosphorus. UNEP Year Book 2011.
P = essential macronutrientP is required in:hydroxyapatite, amino acids, nucleic acids, O 43 kgphospholipids, ATP, creatine phosphateAdults must ingest 0.7 g P/day in their food.Children, adolescents, and pregnant women shouldconsume 1.25 g/day.Symptoms of P deficiency (hypophosphatemia):loss of appetite, muscle weakness, bone pain, Crickets, fragile bones, increased susceptibility to 16 kginfection, numbness and tingling of the extremities,difficulty walking H 7 kgSevere hypophosphatemia results in death. N, 1.8 kg Ca, 1.0 kg P, 0.8 kg other, 0.4 kg
World phosphorus supply 0.5 Bt phosphate rock has been extracted over the past half-century. Current global extraction rate is 20 Mt/year. Production is increasing at 2.5 % / year.K. Ashley, D. Cordell, D. Mavinic, “A brief history of phosphorus: From the philosopher’s stone to nutrient recovery and reuse”, Chemosphere, 2011, 84, 737.
Mining phosphate rock Phosphorite, a sedimentary rock 15-20 % phosphate, as Ca5(PO4)3X (X = F, OH) Open-cast mining of phosphate rockTogo Florida Phillippe Diederich for The New York Tim Florida mines pump 100,000 gallons water/min. Rock may contain elevated levels of toxic metals (Cr, Cd, Pb, Hg). Each ton of mined rock generates 5 tons radioactive (U, Th) phosphogypsum.
Phosphate use efficiencyP recoveries from phosphaterock can be as low as 40%. Only 20% of mined phosphate ends up in the food we consume.
Peak phosphorus?Peak phosphorus curve derived from US Geological Survey and industry data, indicating peak production ca. 2035. Cordell, D.; Drangert, J.-O.; White, S. The story of phosphorus: Global food security and food for thought. Glob. Environ. Change 2009, 19, 292.
Global phosphate reservesLargest current producers: China (38%), US (15%), Morocco (14%), Russia (6%)
Future P-rock needs Estimated reserves will last 300-400 years at current production rates. Growing world population, food equity, and changing dietary preferences (increased protein consumption) could reduce this to 50-100 years.D. Cordell and S. White, “Peak Phosphorus: Clarifying the Key Issues of a Vigorous Debate about Long-Term Phosphorus Security”, Sustainability 2011, 3, 2027
Supply/price instability • Prices shot up in 2007–2008, due to increasing demand driven by more meat- and dairy-rich diets, especially in China and India, and to expansion of the biofuels industry. • In 2008, China imposed a 135 % tariff on phosphate rock, effectively eliminating exports. It was lifted in 2009, but new peak season tariffs were introduced in 2011 and remain in effect. • Phosphate recovery becomes economically viable at $100/t.“Failure to take a systems approach could result in investment in costly and energy-intensive phosphorus recovery technologies that do not address the whole system andhence do not provide the greatest outcome for sustainability, or at worst, conflict with otherrelated services (such as energy supply).” Cordell, 2011
P-recovery from citiesHumans excrete 3 Mt P annually (0.4 kg/person/yr).Some forms struvite, MgNH4PO4.6H2O (MAP).Potential use as slow-release fertilizer.Conventional precipitation-sedimentation- Pipe clogged with struvite, due to increase infiltration is energy-intensive, and product has phosphate concentration during biologicalhigh water content (60-80 %). wastewater treatment.In 2012, a municipal Nutrient Recovery Facilityopened in Hillsboro, Oregon. It will produce 1200tons/yr of CrystalGreen fertilizer.Ostara reports seven times less energy requiredto create Crystal Green than conventionalfertilizer. www.ostara.com
Crystallization in liquid Crystalactor® fluidized bed• MgNH4PO4.6H2O is obtained by mixing feed with MgCl2 and (if necessary) NaOH• Difficult separation of fine crystals • fluidized bed crystallizer uses seed (sand or minerals) to induce pellet formation • product discharged continuously at bottom • high purity pellets with low water content (< 5%) www.dhv.comPhosphate recovery plant in Westerbork, The NetherlandsOther potential P-recovery approaches: adsorption, ion-exchange, nanofiltration.
Closing the P-cycle1. Improve recovery of phosphate from phosphate rock, while mitigating impact of waste.2. Replace as much primary input as possible by secondary input (recycled P) • Devise efficient ways to recycle P from animal waste • Recycle P from other phosphorus uses (e.g., phosphines and phosphine oxides used in chemical processing, phosphors used in lighting) • Capture P from diffuse sources (detergents in graywater, farm runoff) K. Lammertsma, Amsterdam
Extracting by-products mining Cu ore British Geological Survey 1 1 ppm Re crushing, milling, flotation 2 concentrates Mo molybdenite 100 ppm Re Re metal during roasting, Re2O7 3 sublimes in flue gas 500 ppm Re Re2O7 is dissolved in 4 weak acid solutionRe annual production 50 tons; supply is inelastic. 1000 ppm ReUsed in gas turbines and jet turbines, where fuel efficiency organic solvent extraction 5increases with operating temperature. In some super-alloys, 2% ReRe is unsubstitutable. ion-exchange then 6 crystallization as Projected need for 30,000 new, fuel-efficient passenger NH4ReO4, 69% Re planes by 2030. Supply > demand; Re price $12,000/kg in 8/2008. reduction by H2 to metal• Need to increase extraction efficiency from ores 7 > 99.9% Re• Reduce dependence on strong acid solutions during processing• Develop methods to extract Re from alloys for recycleM. Carducci, D. Honecker, Climax Molybdenum
Process intensification Replace batch reactors with continuous microflow reactors - superior mixing and heat transfer properties - safer handling of hazardous intermediates - possibility of using short-lived reactants - easy to ‘number-up’ Need to couple with appropriately scaled separations systemsK. Jensen et al., Angew. Chem. Int. Ed. 2007, 46, 5704 K. Jensen et al., Angew. Chem. Int. Ed. 2010, 49, 899
New membrane materials Inorganic-organic hybrid membranes combine the separating ability of the porous inorganic component with the processibility and scaleability of the organic component. Nanodispersion of the inorganic filler increases discrimination between molecules of different sizes. Potential uses in CO2 and H2S capture. AMH-33D porous layered silicate surface functionalized dispersed in cellulose with organosilane acetate (CA) S. Nair, Georgia Tech
Chemicals from renewables A = Hydrolysis B = Isomerization C = Dehydration D = Rehydration E= Hydrogenation F = Hydrogenolysis N. Cardona-Martínez, UPRM-Mayagüez
Educational needs• Prepare a qualified, knowledgeable workforce to thinkabout how its actions affect the sustainability of theprocess/product/company/etc.- Train students in systems-level thinking, economic and safety analyses using case studies- Ask students to conduct life cycle and material flow analyses- Expose students to industrial research and design with constraints- Have students reflect on scaleability, materials availability, desired lifetime and recyclability- Cultivate communication skills with stakeholders, including the public • Emphasize multidisciplinary teamwork (physical scientists/engineers/social scientists) • Make sustainability training part of professional accreditation requirements (ACS, ABET, AIChE, TMS, ACerS, MRS) • Empower students to create change through innovation training and experiences
AcknowledgementsSusChEM Co-chair Jim McGuffin-Cawley (Case Western Reserve)NSF Division Directors Matt Platz (CHE), Jim McGrath (CBET), and Ian Robertson (DMR)Many NSF Program Officer observers, especially Kathy Covert, Tingyu Li, and Lynnette MadsenAll SusChEM workshop participants, from academia, industry, and government, especially our grad students
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