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Effect of iron oxide on phosphate sorption by calcite and calcareous soils
Author(s) -
HAMAD M. E.,
RIMMER D. L.,
SYERS J. K.
Publication year - 1992
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.1365-2389.1992.tb00135.x
Subject(s) - calcite , sorption , carbonate , oxide , iron oxide , carbonate minerals , calcium carbonate , calcareous , chemistry , soil water , phosphate , calcareous soils , inorganic chemistry , mineralogy , environmental chemistry , geology , adsorption , soil science , paleontology , organic chemistry
SUMMARY Pure calcite (AR grade CaCO 3 ) was treated with ferrous perchlorate solution to give a surface coating of iron (Fe) oxide. Maximum sorption ( x m ) of phosphate (P) by the calcite increased from 18.2 to 160 mg P kg −1 as the amount of coating increased from 0.00 to 16.0 g Fe 2 O 3 , kg −1 CaCO 3 . Evidence for Fe oxide coatings on carbonate minerals in two Sudanese soils was obtained by optical microscopy and electron‐probe microanalysis. The relative contributions of carbonate and Fe oxide minerals, and Fe oxide coatings to P sorption in these soils were calculated, based on an assumed model of oxide distribution. Separate‐phase Fe oxide was the major contributor (30–40%) to P sorption in the soils; the Fe oxide coatings on carbonate minerals were only minor contributors (< 6%), and the contribution of uncoated carbonate minerals was found to be negligible (<1 %). These results suggest a very minor role for carbonate minerals, even when coated with Fe oxide, in the sorption of P by these calcareous, Sudanese soils.