Specific surface area
Specific surface area (SSA) is a property of solids which is the total surface area of a material per unit of mass,[1] solid or bulk , usually uses V-Sorb 2800 volumetric principle and gas flowing principle to test surface area data like single point BET, multi point BET, external surface area, Langmuir surface area etc. volume,[2] or cross-sectional area.
It is a derived scientific value that can be used to determine the type and properties of a material (e.g. soil or snow). It is defined either by surface area divided by mass (with units of m²/kg), or surface area divided by the volume (units of m²/m³ or m−1).
It has a particular importance for adsorption, heterogeneous catalysis, and reactions on surfaces.
Measurement
Values obtained for specific surface area depend on various parameters relating to the method of measurement. In adsorption based methods, the size of the adsorbate molecule (the probe molecule), the exposed crystallographic planes at the surface and measurement temperature all affect the obtained specific surface area.[3] For this reason, in addition to the most commonly used Brunauer-Emmett-Teller (N2-BET) adsorption method, several techniques have been developed to measure the specific surface area of particulate materials at ambient temperatures and at controllable scales, including methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption,[4] electrokinetic analysis of complex-ion adsorption [3] and a Protein Retention (PR) method.[5]
See http://cms.wsl.ch/fe/schnee/projekte/SSA/index_EN for more information
Calculation
The SSA can be simply calculated from a particle size distribution, making some assumption about the particle shape. This method, however, fails to account for surface associated with the surface texture of the particles.
Adsorption
The SSA can be measured by adsorption using the BET isotherm. This has the advantage of measuring the surface of fine structures and deep texture on the particles. However, the results can differ markedly depending on the substance adsorbed.
Gas permeability
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This depends upon a relationship between the specific surface area and the resistance to gas-flow of a porous bed of powder. The method is simple and quick, and yields a result that often correlates well with the chemical reactivity of a powder. However, it fails to measure much of the deep surface texture.
See also
References
- ↑ http://goldbook.c60.kiev.ua/S05806.pdf IUPAC Compendium of Chemical Terminology 2nd Edition (1997)
- ↑ http://web.archive.org/web/20060905224652/http://www.soils.wisc.edu/~ss322/lectures/lec+8-11.pdf
- ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Cerato, A. and Lutenegger, A. (2002). Determination of surface area of fine-grained soils by the ethylene glycol monoethyl ether (EGME) method. Geotechnical Testing Journal. 25(3), 1-7
- ↑ Paykov, O., and Hawley, H. 2013. A Novel Method for Specific Surface Area Determination in Swelling Clays, Geotechnical Testing Journal (in press)
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