Premium
Adsorption of Orthophosphate to Humic‐Fe‐Complexes and to Amorphous Fe‐Oxide
Author(s) -
Gerke Jörg,
Hermann Reinhold
Publication year - 1992
Publication title -
zeitschrift für pflanzenernährung und bodenkunde
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 0044-3263
DOI - 10.1002/jpln.19921550313
Subject(s) - adsorption , chemistry , humic acid , amorphous solid , inorganic chemistry , oxide , metal , hydrous ferric oxides , molar ratio , nuclear chemistry , organic chemistry , sorption , catalysis , fertilizer
The adsorption of orthophosphate to humic surfaces was studied in a model experiment. The adsorption maximum of humic substances greatly increased with higher concentrations of organically complexed Fe (III), indicating that orthophosphate was bound to humic surfaces via metal bridges. The molar ratio P adsorbed /Fe was nearly 1 for Fe freshly complexed to humic substances, whereas the ratio for amorphous Fe‐oxide was a tenfold lower. An increase in pH from 5.2 to 6.2 lead to an increase of P‐adsorption of about 30% in the case of humic‐Fe‐surfaces, which could be explained by an increased accessibility of adsorption sites at pH 6.2. The addition of a 0.01 M CaCl 2 ‐matrix increased orthophosphate adsorption at pH 6.2 but not at pH 5.2. This could be explained by electrostatic interactions caused by the Ca ++ ion.