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Adsorption of Aluminum by a Smectite: II. An Al 3+ ‐Ca 2+ Exchange Model
Author(s) -
McBride M. B.,
Bloom P. R.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100060011x
Subject(s) - adsorption , chemistry , ion exchange , langmuir adsorption model , montmorillonite , inorganic chemistry , clay minerals , precipitation , ion , mineralogy , physics , organic chemistry , meteorology
The adsorption of Al by Ca 2+ ‐montmorillonite has been found to be described by a Langmuir‐type equation in which the activity of Al 3+ in solution is a function of the coverage of the mineral surfaces by Al. The classical mass‐action equations were inadequate in describing the exchange reaction where the Ca 2+ activity was allowed to vary, weighting the effect of the Ca 2+ ion activity on the equilibrium too heavily. The model suggests the relative solutionlike nature of adsorbed Ca 2+ compared to the much more strongly adsorbed Al 3+ . Hydrolysis and precipitation reactions of Al 3+ at higher pH complicated the exchange model by introducing significant quantities of adsorbed hydroxyl‐Al into the system.