Editing Adsorption (section)

{{Short description|Phenomenon of surface adhesion}}
{{distinguish|text=[[Absorption (chemistry)|Absorption]]}}
{{See also|Physisorption|Chemisorption|Segregation (materials science)}}
[[Image:BET Multilayer Adsorption.svg|thumb|Brunauer, Emmett and Teller's [[#BET|model]] of multilayer adsorption is a random distribution of molecules on the material surface.]]

'''Adsorption''' is the [[adhesion]]<ref>{{Cite web |last=Guruge |first=Amila Ruwan |date=2021-02-17 |title=Absorption Vs Adsorption |url=https://www.arhse.com/absorption-vs-adsorption/ |access-date=2023-11-26 |website=Chemical and Process Engineering |language=en-US}}</ref> of [[atoms]], [[ion]]s or [[molecule]]s from a gas, liquid or dissolved solid to a [[Surface science|surface]].<ref>{{cite web |url=http://www.brownfieldstsc.org/glossary.cfm?q=1 |archive-url=https://web.archive.org/web/20080218094403/http://www.brownfieldstsc.org/glossary.cfm?q=1 |url-status=dead |archive-date=2008-02-18 |title=Glossary |publisher=The Brownfields and Land Revitalization Technology Support Center |access-date=2009-12-21 }}</ref> This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from [[absorption (chemistry)|absorption]], in which a [[fluid]] (the ''absorbate'') is [[Dissolution (chemistry)|dissolved]] by or [[permeation|permeates]] a liquid or solid (the ''absorbent'').<ref>{{cite web |url=http://www.memidex.com/absorption+chemistry |title=absorption (chemistry) |work=Memidex (WordNet) Dictionary/Thesaurus |access-date=2010-11-02 |archive-url=https://web.archive.org/web/20181005080455/http://www.memidex.com/absorption+chemistry |archive-date=2018-10-05 |url-status=dead }}</ref> 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.<ref>{{Cite book|last1=Atkins |first1=P. W. |last2=De Paula |first2=Julio |last3=Keeler |first3=James |title=Atkins' Physical chemistry |year=2018 |isbn=978-0-19-876986-6 |edition=Eleventh |location=Oxford, United Kingdom |oclc=1020028162}}{{page needed|date=June 2022}}</ref> The term ''[[sorption]]'' encompasses both adsorption and absorption, and ''[[desorption]]'' is the reverse of sorption.

{{Quote box|width = 35%
 |title = [[International Union of Pure and Applied Chemistry|IUPAC]] definition
 |quote = '''adsorption''': An increase in the concentration of a dissolved substance at the [https://doi.org/10.1351/goldbook.I03082 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. <ref name='Gold Book "adsorption"'>{{cite journal |title=adsorption |url=https://goldbook.iupac.org/terms/view/A00155 |website=Gold Book |date=2014 |publisher=IUPAC |access-date=1 April 2024 |ref=Gold Book A00155 |doi=10.1351/goldbook.A00155|doi-access=free }}</ref>
}}

Like [[surface tension]], adsorption is a consequence of [[surface energy]]. In a bulk material, all the bonding requirements (be they [[ionic bond|ionic]], [[covalent bond|covalent]] or [[metallic bond|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 force]]s) or [[chemisorption]] (characteristic of covalent bonding). It may also occur due to electrostatic attraction.<ref>{{cite journal |journal=[[Journal of Colloid and Interface Science|J. Colloid Interface Sci.]] |year=2010 |volume=347 |issue=1 |pages=15–24 |title=Interaction of cement model systems with superplasticizers investigated by atomic force microscopy, zeta potential, and adsorption measurements |last1=Ferrari |first1=L. |last2=Kaufmann |first2=J. |last3=Winnefeld |first3=F. |last4=Plank |first4=J. |doi=10.1016/j.jcis.2010.03.005 |pmid=20356605|bibcode=2010JCIS..347...15F }}</ref><ref>{{cite journal |last1=Khosrowshahi |first1=Mobin Safarzadeh |last2=Abdol |first2=Mohammad Ali |last3=Mashhadimoslem |first3=Hossein |last4=Khakpour |first4=Elnaz |last5=Emrooz |first5=Hosein Banna Motejadded |last6=Sadeghzadeh |first6=Sadegh |last7=Ghaemi |first7=Ahad |title=The role of surface chemistry on CO2 adsorption in biomass-derived porous carbons by experimental results and molecular dynamics simulations |journal=Scientific Reports |date=26 May 2022 |volume=12 |issue=1 |pages=8917 |doi=10.1038/s41598-022-12596-5 |pmid=35618757 |pmc=9135713 |bibcode=2022NatSR..12.8917K |s2cid=249096513 }}</ref> 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.<ref>{{Cite journal |last1=Carroll |first1=Gregory T. |last2=Jongejan |first2=Mahthild G. M. |last3=Pijper |first3=Dirk |last4=Feringa |first4=Ben L. |date=2010 |title=Spontaneous generation and patterning of chiral polymeric surface toroids |url=http://xlink.rsc.org/?DOI=c0sc00159g |journal=Chemical Science |language=en |volume=1 |issue=4 |pages=469 |doi=10.1039/c0sc00159g |s2cid=96957407 |issn=2041-6520}}</ref>

Adsorption is present in many natural, physical, biological and chemical systems and is widely used in industrial applications such as [[heterogeneous catalysts]],<ref>{{cite journal |last1=Czelej |first1=K. |last2=Cwieka |first2=K. |last3=Kurzydlowski |first3=K.J. |title=CO<sub>2</sub> stability on the Ni low-index surfaces: Van der Waals corrected DFT analysis|journal=Catalysis Communications |date=May 2016 |volume=80 |issue=5 |pages=33–38 |doi=10.1016/j.catcom.2016.03.017 }}</ref><ref>{{cite journal |last1=Czelej |first1=K. |last2=Cwieka |first2=K. |last3=Colmenares |first3=J.C. |last4=Kurzydlowski |first4=K.J. |title=Insight on the Interaction of Methanol-Selective Oxidation Intermediates with Au- or/and Pd-Containing Monometallic and Bimetallic Core@Shell Catalysts |journal=Langmuir |year=2016 |volume=32 |issue=30 |pages=7493–7502 |doi=10.1021/acs.langmuir.6b01906 |pmid=27373791 }}</ref> [[activated charcoal]], capturing and using [[waste heat]] to provide cold water for air conditioning and other process requirements ([[#Adsorption chillers|adsorption chillers]]), [[synthetic resins]], increasing storage capacity of [[Tunable nanoporous carbon|carbide-derived carbons]] and [[water purification]].<ref>{{Cite journal |last1=Ali |first1=Shimaa M. |last2=Ashour |first2=Basma |last3=Farahat |first3=Mohamed G. |last4=El-Sherif |first4=Rabab M. |date=September 2024 |title=Biomass-based perovskite/graphene oxide composite for the removal of organic pollutants from wastewater |url=https://linkinghub.elsevier.com/retrieve/pii/S0272884224042573 |journal=Ceramics International |volume=50 |issue=23 |pages=49085–49094 |language=en |doi=10.1016/j.ceramint.2024.09.249|url-access=subscription }}</ref> 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|date=November 2013}} are lesser known.

The word "adsorption" was coined in 1881 by German physicist [[Heinrich Kayser]] (1853–1940).<ref>
{{cite journal
 |last1=Kayser |first1=Heinrich
 |year=1881
 |title=Über die Verdichtung von Gasen an Oberflächen in ihrer Abhängigkeit von Druck und Temperatur
 |url=https://books.google.com/books?id=ZxVbAAAAYAAJ&pg=PA526
 |journal=Annalen der Physik und Chemie
 |volume=248 |issue=4 |pages=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: {{lang|de|"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.")</ref>