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TIME‐DEPENDENT SORPTION OF PHOSPHATE BY SOILS AND HYDROUS FERRIC OXIDES
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.tb02266.x
Subject(s) - sorption , goethite , chemistry , inorganic chemistry , ferric , phosphate , soil water , hydrous ferric oxides , dithionite , bicarbonate , hematite , mineralogy , adsorption , geology , organic chemistry , soil science , enzyme
Summary The sorption of inorganic phosphate (P) by soils and hydrous ferric oxides was studied at times up to 192h. An initially rapid decrease in solution P concentration was followed by a much slower decrease between 48 and 192h with soils, Fe gel. and natural goethite, whereas synthetic goethite gave a well‐defined equilibrium condition after only 48h. Resolution of the sorption isotherms showed that the increase in P sorption with time involved an appreciable shift of P from a more‐physically sorbed form to a chemisorbed form. This was supported by chemical fractionation which showed that NaOH‐extractable P was fairly constant with increasing sorption time, whereas the additional sorbed P was extracted by citrate‐dithionite‐bicarbonate from soils, and by HC1 from Fe gel and natural goethite. These sorbents contained short‐range (amorphous) material, whereas synthetic goethite, from which all sorbed P was NaOH –extractable. did not. It is proposed that the time‐dependent sorption of P and the associated shift of P to chemisorbed forms, involves the diffusion of P into “structurally porous”, short‐range order material.