Just read a lot of textbooks and papers on this subject. It seems that sorption is so much more favored than desorption within specialized literature. The very definition of these concepts is of utmost importance not only for epistemological purposes, but also for methodological issues.
Here is the first paragraph of an article for an encyclopaedia on "Sorption phenonema".
The word “adsorption” is familiar to most of us. It simply
means that a substance is attached to the outside of a solid.
Or to use more formal language, the concentration of a substance
is greater at the surface of a phase than it is in the bulk.
However, sometimes it is not clear that the substance is really
restricted to the outside. Because it can be difficult to separate
the adsorbed material from the absorbed, the noncommittal
term “sorption” is often preferred. The term has a long scientific
history going back to 1909 (McBain, 1909). In soil science
it is used to indicate all processes that result in the transfer of
material from the soil solution to the solid phase. It therefore
includes adsorption.
From
Sorption phenomena. Pp 745-756 In Encyclopedia of Soil Science Ed Ward Chesworth. Springer, Dordrecht, the Netherlands.
Professor Lambers, thank you for your answer. What a lovely definition of sorption phenomena. Sposito and Tan agree with this paragraph in their text books. But what about the desorption phenomena? Can I just say that is a sorption back fowards?
To some extent you can indeed say that, Guilherme. However, the reality is more complicated. What is adsorbed onto soil particle,s can be desorbed relatively easily, but what actually enters deep into soil particles is much harder to desorb. Regards, Hans
Guilherme: Desorption is detachment of solute from soil into water. Thus, the rate of desorption depends on the state of solute in soil (e.g., how deep it move inside pores, whether it form specific bond on soil minerals etc). Whereas in sorption, solute is free in water and can move freely towards soil. Nevertheless, both sorption and desorption depend on chemical conditions of water (pH, ionic strength, solute concentration in both phases, co solute concentration). As you mentioned, books by Sposito or Tan cover a lot about sorption because it has more applications -- removal of contaminants from water.
I would like to know, does adsorption (e.g., chemical adsorption) also includes ion exchange? There are people how say "yes" and people, who say "no"!
It most certainly does, going back to the paper in 1909 referred to above. In soil science the non-committal term sorption is used to indicate all processes that result in the transfer of material from the soil solution to the solid phase.
The complete reference of the paper where the term "sorption" was coined is:
McBain JW 1909 The mechanism of the adsorption (“sorption”) of hydrogen by carbon. Philosophical Magazine Series 6 18:916-935.
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