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Macroscopic Experimental and Modeling Evaluation of Selenite and Selenate Adsorption Mechanisms on Gibbsite
Author(s) -
Goldberg Sabine
Publication year - 2014
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/sssaj2013.06.0249
Subject(s) - selenate , gibbsite , ionic strength , point of zero charge , chemistry , adsorption , selenium , arsenate , inorganic chemistry , inner sphere electron transfer , surface charge , phosphate , ionic bonding , ion , mineralogy , aqueous solution , arsenic , kaolinite , organic chemistry
Selenite Se(IV) and selenate Se(VI) adsorption behavior was investigated on gibbsite as a function of solution pH and solution ionic strength. Adsorption of both Se redox states decreased with increasing solution pH. Electrophoretic mobility measurements showed downward shifts in point of zero charge (PZC) indicative of the formation of inner‐sphere Se(IV) and Se(VI) surface complexes. However, the downward shift was less than for strongly adsorbing anions such as phosphate and arsenate, suggesting that outer‐sphere surface complexes are also present. The triple layer model, a chemical surface complexation model, was well able to describe Se(IV) and Se(VI) adsorption as a function of solution pH and solution ionic strength by simultaneously optimizing both inner‐sphere and outer‐sphere surface complexation constants. Direct spectroscopic investigations of selenite surface configuration are needed to corroborate the species suggested by the macroscopic experiments and obtained from the triple layer model optimizations.