Adsorption

Not to be confused with Absorption.
See also: Physisorption, Chemisorption, and Segregation (materials science)
Brunauer, Emmett and Teller's model of multilayer adsorption is a random distribution of molecules on the material surface.

Adsorption is the adhesion[1] of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface.[2] This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid (the absorbate) is dissolved by or permeates a liquid or solid (the absorbent).[3] While adsorption does often precede absorption, which involves the transfer of the absorbate into the volume of the absorbent material, alternatively, adsorption is distinctly a surface phenomenon, wherein the adsorbate does not penetrate through the material surface and into the bulk of the adsorbent.[4] The term sorption encompasses both adsorption and absorption, and desorption is the reverse of sorption.

IUPAC definition

adsorption: An increase in the concentration of a dissolved substance at the interface of a condensed and a liquid phase due to the operation of surface forces. Adsorption can also occur at the interface of a condensed and a gaseous phase. [5]

Like surface tension, adsorption is a consequence of surface energy. In a bulk material, all the bonding requirements (be they ionic, covalent or metallic) of the constituent atoms of the material are fulfilled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms and therefore can attract adsorbates. The exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption (characteristic of weak van der Waals forces) or chemisorption (characteristic of covalent bonding). It may also occur due to electrostatic attraction.[6][7] The nature of the adsorption can affect the structure of the adsorbed species. For example, polymer physisorption from solution can result in squashed structures on a surface.[8]

Adsorption is present in many natural, physical, biological and chemical systems and is widely used in industrial applications such as heterogeneous catalysts,[9][10] activated charcoal, capturing and using waste heat to provide cold water for air conditioning and other process requirements (adsorption chillers), synthetic resins, increasing storage capacity of carbide-derived carbons and water purification.[11] Adsorption, ion exchange and chromatography are sorption processes in which certain adsorbates are selectively transferred from the fluid phase to the surface of insoluble, rigid particles suspended in a vessel or packed in a column. Pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts thereof,[citation needed] are lesser known.

The word "adsorption" was coined in 1881 by German physicist Heinrich Kayser (1853–1940).[12]

  1. ^ Guruge, Amila Ruwan (2021-02-17). "Absorption Vs Adsorption". Chemical and Process Engineering. Retrieved 2023-11-26.
  2. ^ "Glossary". The Brownfields and Land Revitalization Technology Support Center. Archived from the original on 2008-02-18. Retrieved 2009-12-21.
  3. ^ "absorption (chemistry)". Memidex (WordNet) Dictionary/Thesaurus. Archived from the original on 2018-10-05. Retrieved 2010-11-02.
  4. ^ Atkins, P. W.; De Paula, Julio; Keeler, James (2018). Atkins' Physical chemistry (Eleventh ed.). Oxford, United Kingdom. ISBN 978-0-19-876986-6. OCLC 1020028162.{{cite book}}: CS1 maint: location missing publisher (link)[page needed]
  5. ^ "adsorption". Gold Book. IUPAC. 2014. doi:10.1351/goldbook.A00155. Retrieved 1 April 2024.
  6. ^ Ferrari, L.; Kaufmann, J.; Winnefeld, F.; Plank, J. (2010). "Interaction of cement model systems with superplasticizers investigated by atomic force microscopy, zeta potential, and adsorption measurements". J. Colloid Interface Sci. 347 (1): 15–24. Bibcode:2010JCIS..347...15F. doi:10.1016/j.jcis.2010.03.005. PMID 20356605.
  7. ^ Khosrowshahi, Mobin Safarzadeh; Abdol, Mohammad Ali; Mashhadimoslem, Hossein; Khakpour, Elnaz; Emrooz, Hosein Banna Motejadded; Sadeghzadeh, Sadegh; Ghaemi, Ahad (26 May 2022). "The role of surface chemistry on CO2 adsorption in biomass-derived porous carbons by experimental results and molecular dynamics simulations". Scientific Reports. 12 (1): 8917. Bibcode:2022NatSR..12.8917K. doi:10.1038/s41598-022-12596-5. PMC 9135713. PMID 35618757. S2CID 249096513.
  8. ^ Carroll, Gregory T.; Jongejan, Mahthild G. M.; Pijper, Dirk; Feringa, Ben L. (2010). "Spontaneous generation and patterning of chiral polymeric surface toroids". Chemical Science. 1 (4): 469. doi:10.1039/c0sc00159g. ISSN 2041-6520. S2CID 96957407.
  9. ^ Czelej, K.; Cwieka, K.; Kurzydlowski, K.J. (May 2016). "CO2 stability on the Ni low-index surfaces: Van der Waals corrected DFT analysis". Catalysis Communications. 80 (5): 33–38. doi:10.1016/j.catcom.2016.03.017.
  10. ^ Czelej, K.; Cwieka, K.; Colmenares, J.C.; Kurzydlowski, K.J. (2016). "Insight on the Interaction of Methanol-Selective Oxidation Intermediates with Au- or/and Pd-Containing Monometallic and Bimetallic Core@Shell Catalysts". Langmuir. 32 (30): 7493–7502. doi:10.1021/acs.langmuir.6b01906. PMID 27373791.
  11. ^ Ali, Shimaa M.; Ashour, Basma; Farahat, Mohamed G.; El-Sherif, Rabab M. (September 2024). "Biomass-based perovskite/graphene oxide composite for the removal of organic pollutants from wastewater". Ceramics International. doi:10.1016/j.ceramint.2024.09.249.
  12. ^ Kayser, Heinrich (1881). "Über die Verdichtung von Gasen an Oberflächen in ihrer Abhängigkeit von Druck und Temperatur". Annalen der Physik und Chemie. 248 (4): 526–537. Bibcode:1881AnP...248..526K. doi:10.1002/andp.18812480404.. In this study of the adsorption of gases by charcoal, the first use of the word "adsorption" appears on page 527: "Schon Saussure kannte die beiden für die Grösse der Adsorption massgebenden Factoren, den Druck und die Temperatur, da er Erniedrigung des Druckes oder Erhöhung der Temperatur zur Befreiung der porösen Körper von Gasen benutzte." ("Saussaure already knew the two factors that determine the quantity of adsorption – [namely,] the pressure and temperature – since he used the lowering of the pressure or the raising of the temperature to free the porous substances of gases.")