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Competitive Coefficients for the Adsorption of Arsenate, Molybdate, and Phosphate Mixtures by Soils
Author(s) -
Roy W. R.,
Hassett J. J.,
Griffin R. A.
Publication year - 1986
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/sssaj1986.03615995005000050017x
Subject(s) - arsenate , molybdate , adsorption , chemistry , phosphate , inorganic chemistry , loam , soil water , arsenic , geology , organic chemistry , soil science
The adsorption behavior of anionic mixtures (binary‐solute combinations of arsenate, molybdate, and phosphate) by three soils (Cecil clay [Typic Hapludults], EPA‐14 [Ultisol], and Catlin silt loam [Typic Argiudolls]) was investigated using the Sheindorf‐Rebhun‐Sheintuch (SRS) equation. The SRS equation is a multicomponent Freundlich‐type adsorption equation. Most of the isotherm data were found to conform to linear SRS expressions, making it possible to derive competitive coefficients on a concentration basis for each binary‐solute system. The adsorption of arsenate and molybdate by all three soils were significantly reduced by the presence of phosphate, which was attributed to competitive interactions. In each solute‐soil system, the adsorption of phosphate was not greatly suppressed by either arsenate or molybdate. The adsorption of arsenate by Cecil clay and EPA‐14 was reduced in the presence of molybdate, whereas arsenate did not compete strongly with molybdate adsorption. In contrast, the adsorption of arsenate by Catlin appeared to be independent of molybdate, while the presence of arsenate lowered molybdate adsorption. In general, the associated competitive coefficient for each solute‐soil system appeared to be consistent with qualitative observations, and was viewed as a single‐valued term indicative of the relative affinity of each soil for a given anion with respect to a competing anion from a binary‐solute mixture.