Specific surface area

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title: "Specific surface area" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["porous-media", "surface-science", "mass-specific-quantities"] description: "Total surface of a finely divided solid per unit of mass" topic_path: "general/porous-media" source: "https://en.wikipedia.org/wiki/Specific_surface_area" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Total surface of a finely divided solid per unit of mass ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/f/fe/Surface_specifique_et_rayures.svg" caption="Scratches, represented by triangular-shaped grooves, make the surface area greater."] ::

Specific surface area (SSA) is a property of solids defined as the total surface area (SA) of a material per unit mass, (with units of m2/kg or m2/g). Alternatively, it may be defined as SA per solid or bulk volume (units of m2/m3 or m−1).

It is a physical value that can be used to determine the type and properties of a material (e.g. soil or snow). It has a particular importance for adsorption, heterogeneous catalysis, and reactions on surfaces.

Measurement

::figure[src="https://upload.wikimedia.org/wikipedia/commons/4/4e/RaschigRings005.JPG" caption="Ceramic [[Raschig rings]]..."] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/97/Bialecki_rings.jpg" caption="...and plastic Białecki rings of increased SSA"] ::

Values obtained for specific surface area depend on 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.{{cite journal| last1=Hanaor| first1=D.A.H.| last2=Ghadiri| first2=M. | last3=Chrzanowski| first3=W.| last4=Gan| first4=Y.| title= Scalable Surface Area Characterization by Electrokinetic Analysis of Complex Anion Adsorption| journal= Langmuir| year=2014| volume=30| issue=50| pages=15143–15152 | url=http://drgan.org/wp-content/uploads/2015/05/025_Langmuir_2014.pdf| doi=10.1021/la503581e| pmid=25495551| arxiv=2106.03411| s2cid=4697498}} 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, electrokinetic analysis of complex-ion adsorption and a Protein Retention (PR) method. A number of international standards exist for the measurement of specific surface area, including ISO standard 9277.

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. The BET theory has inherent limitations but has the advantage to be simple and to yield adequate relative answers when the solids are chemically similar. In relatively rare cases, more complicated models based on thermodynamic approaches, or even quantum chemistry, may be applied to improve the consistency of the results, but at the cost of much more complex calculations requiring advanced knowledge and a good understanding from the operator.

Gas permeability

Main article: Air permeability specific surface

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.

::data[format=table title="Selected Materials with High Surface Areas"]

Typical surface area (m2/g)	Material	Application
7140	Metal–organic framework	gas absorption
900	Faujasite	catalyst
500–3000	activated carbon	gas and solute absorption
200	alumina	catalyst support
::

References

References

1. "specific surface area".
2. "Surface Area".
3. "Characterization of porous silicon integrated in liquid chromatography chips".
4. (1 September 2002). "Determination of surface area of fine-grained soils by the ethylene glycol monoethyl ether (EGME) method". Geotechnical Testing Journal.
5. (1 July 2013). "A Protein-Retention Method for Specific Surface Area Determination in Swelling Clays". [[ASTM]].
6. "ISO 9277:2010(en) Determination of the specific surface area of solids by gas adsorption — BET method".
7. Condon, James. (2020). "Surface Area and Porosity Determinations by Physisorption, 2nd edition". Elsevier.
8. (2018). "Balancing Mechanical Stability and Ultrahigh Porosity in Crystalline Framework Materials". Angewandte Chemie International Edition.
9. (2018). "Specific Surface Area Determination for Microporous/Mesoporous Materials: The Case of Mesoporous FAU-Y Zeolites". Langmuir.
10. (1950). "Alumina Surface Area Measurements". Industrial & Engineering Chemistry.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::