Gas adsorption technique
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This document discusses the gas adsorption technique for determining surface area of solids. It works based on the BET theory of gas molecules physically adsorbing onto surfaces. The technique involves pretreating a solid sample under heat and vacuum to remove contaminants, then exposing it to incremental doses of an adsorptive gas like nitrogen at cryogenic temperatures. By measuring the quantity of gas adsorbed at each pressure, an adsorption isotherm can be generated to determine the monolayer capacity and calculate the surface area based on the area each adsorbed gas molecule covers. The gas adsorption technique can measure pores between 0.4-50nm and is an established, easy method for surface area analysis.
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adorbation -air pollution - environment engineering - mechanical engineering
General methods to control gaseous pollutants
The document discusses methods for controlling gaseous pollutants, including absorption, adsorption, and combustion. Absorption involves passing polluted gases through liquid absorbents like in a packed tower, plate tower, or spray tower. Adsorption uses solid adsorbents like activated carbon to concentrate pollutants on surfaces. Combustion destroys pollutants through direct flame, thermal incineration using a residence chamber, or catalytic combustion using catalysts to aid oxidation. Overall, the document outlines common industrial processes for removing gaseous pollutants from emission streams.
BET Analysis.pptx
The BET method is used to accurately measure the total surface area of porous samples based on gas absorption on their surface. It was developed in 1938 by Brunauer, Emmett and Teller to measure the specific surface area of finely divided and porous solids. The BET method operates by measuring the amount of nitrogen gas absorbed and desorbed by a material at liquid nitrogen temperature while gradually increasing and decreasing gas pressure. It uses an equation to calculate the specific surface area based on the absorbed gas volume. While widely used, the BET method has limitations including only measuring accessible surface area and being time-consuming.
Adsorption
Adsorption is the accumulation of atoms, molecules, or ions onto a surface. There are two main types: physical adsorption, which occurs via weak van der Waals forces, and chemical adsorption, which involves chemical bond formation. Factors that affect adsorption include temperature, pressure, and surface area of the adsorbent. Common adsorbents used are silica gel and activated carbon. Adsorption isotherms describe the relationship between amount adsorbed and pressure at constant temperature. Adsorption has applications in air and water purification.
oxygen generation techniques
This document discusses three main techniques for generating oxygen: cryogenic separation, pressure swing absorption (PSA), and membrane technology. Cryogenic separation involves cooling air until its components separate based on their boiling points. PSA uses zeolites in two columns to selectively adsorb nitrogen while allowing oxygen to pass. Membrane technology uses permeable materials to selectively filter oxygen from air faster than nitrogen and argon. Each method can produce 99% pure oxygen at various volumes and costs. Cryogenic separation is most effective for high purity and volume needs, while PSA and membranes are suited for medium-scale production.
Adsorption
Adsorption is the process where gas, liquid, or dissolved molecules accumulate on the surface of a solid or liquid. It is different from absorption, where the substance diffuses into another. Adsorption occurs in natural and industrial systems due to surface energy, and can be described through isotherms relating amount adsorbed to pressure or concentration. Common adsorbents used are activated carbon, silica gel, zeolites, and their characteristics, such as surface area, determine their applications such as purification.
Dust measurement and sampling opk
There are several methods for measuring and sampling dust in foundries where workers are exposed. The most accurate method is the thermal precipitator, which uses an electrically heated wire to deposit dust particles from air onto glass slides that are then examined under a microscope. However, this process is tedious. The Owan's jet counter and Konimeter provide samples but have limitations such as small sample size or inconsistent results between operators. The Hexhlet sampler draws air through stages to collect coarse and fine particles on a paper filter that is weighed to determine dust concentration. Visual methods like the Tyndall beam or smoke generation can also be used to see dust levels. Key dust generation points in foundries include furnace work, sand preparation, core
Atmospheric structure
The document discusses the structure and composition of Earth's atmosphere. It can be summarized as follows:
1) Earth's atmosphere consists of several layers identified by temperature changes with height. It is composed primarily of nitrogen and oxygen, as well as variable amounts of water vapor, carbon dioxide, and other gases.
2) Atmospheric aerosols exist in different sizes ranging from ultrafine to accumulation to coarse modes, which are produced and removed through various natural and human-influenced processes over timescales from minutes to days.
3) The composition and concentrations of atmospheric constituents vary significantly by location from urban to rural to remote areas, and between soluble and insoluble particle types that impact climate and air quality.
Gas Chromatography.pdf
This document summarizes gas chromatography (GC), a common type of chromatography used in analytical chemistry to separate and analyze compounds that can be vaporized without decomposition. It discusses the basic components of a GC system including the carrier gas, sample injection systems, separation columns, detectors, and applications. The key components are the stationary and mobile phases that interact to separate sample compounds based on properties like volatility and polarity. Common detectors discussed are the thermal conductivity detector, flame ionization detector, and mass spectrometer for identifying separated compounds. Applications include analyzing samples from pharmaceuticals, foods, environmental sources, and petrochemicals.
Adsorption separation
Adsorption separation in food processing is discussed in this presentation. Different types of adsorbent generally used are studied. Adsorption types resulting from Vander waal's forces (physisorption) and chemical forces (chemisorption) is highlighted alongwith the different adsorption isotherms- Freundlich, Langmuir and BET isotherms, as well as factors affecting adsorption like temperature, pressure and surface area.
GC.pptx
1. Gas chromatography is a technique used to separate mixtures by injecting a sample into a carrier gas and passing it through a column with a stationary phase. Components are separated based on their interactions and affinity for the stationary and mobile phases.
2. The sample is vaporized and carried by the mobile gas through the column where separation occurs. Components elute at different times depending on their partitioning between the phases.
3. A detector measures the eluting components and outputs signals to show separation as peaks on a chromatogram.
Adam Clegg - An alternative method for modelling flare emissions - DMUG17
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Methane
Methane (CH4) is commonly known as firedamp in coal mines. There are three primary reasons for giving special attention to methane: 1) it is the gas most commonly found in underground coal mines, 2) it has caused more explosions and loss of life than any other cause in mining history, and 3) continued development of methane drainage technology. Methane is formed during the coalification process from decaying organic material and becomes trapped within coal seams. When coal is mined, methane can be released through gradual exudation, gas blowers, or violent outbursts. Due to its light weight, methane also has a tendency to form layers near mine ceilings, which can become explosive if ignition occurs.
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2nd Lecture on Adsorption and Colloids | Chemistry Part II | 11th Std
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Gas adsorption technique
- 4. Gas adsorption • This technique is based on BET theory which aims to explain physical adsorption of gas molecules on solid surface. • Adsorption is a consequence of surface energy
- 10. Langmuir Provides a means of determining surface area based on manolayer coverage of the solid surface by the adsorptive BET The method of Brunauer–Emmett–Teller is employed to determine Surface area on a model of adsorption which incorporates multilayer coverage.
- 15. Gas Adsorption Can measure only open pores Pore size : 0.4 nm – 50 nm Easy Established technique
- 16. Method • Solid pretreated by applying heat, vacuum or flowing gas to remove adsorbed contaminants (water, CO2) • Then solid cooled under vacuum usually to cryogenic temperature(77k or -195 deg C) • Specific dose of adsorptive gas( such as nitrogen, argon, CO2 etc.) is passed on solid surface on regular increments.
- 18. • After each dose of adsorbate , pressure is allowed to equilibrate & quantity adsorbed is calculated. • The quantity adsorbed at each pressure defines adsorption/sorption isotherm
- 20. • From this isotherm quantity of gas required for monolayer formation is determined • Then area covered by each adsorbed gas molecule is known • Finally surface area is determined. • Using gas adsorption technique porosity and pore size can also be calculated.