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MECHANISMS OF PHOSPHATE SORPTION BY SOILS AND HYDROUS FERRIC OXIDE GEL
Author(s) -
RYDEN J. C.,
McLAUGHLIN J. R.,
SYERS J. K.
Publication year - 1977
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1977.tb02297.x
Subject(s) - sorption , chemisorption , inorganic chemistry , chemistry , oxide , sorbent , langmuir , langmuir adsorption model , soil water , phosphate , adsorption , geology , soil science , organic chemistry
Summary Data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (Δ G ) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions. Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more‐physical sorption of P as a potential‐determining ion.