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Fixation Kinetics in Potassium–Iron—Orthophosphate Systems
Author(s) -
Kim Y. K.,
Gurney E. L.,
Hatfield J. D.
Publication year - 1983
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/sssaj1983.03615995004700030012x
Subject(s) - potassium , chemistry , reaction rate constant , kinetics , precipitation , phosphate , nuclear chemistry , analytical chemistry (journal) , inorganic chemistry , chromatography , organic chemistry , physics , quantum mechanics , meteorology
The rate of removal of phosphate and potassium from solution was studied by contacting an iron‐impregnated, cation exchange resin with solutions of monopotassium orthophosphate in concentrations of 0.05 to 0.25 M and with atomic ratios Fe:P from 0.25 to 4.0. The removal of both P and K from solution followed first‐order reaction models for all experimental conditions, the K being removed faster than the P. The rate constants, k 1 and k 2 , for P and K removal, respectively, increased with the ratio Fe:P and were affected to a lesser extent by the initial concentration of KH 2 PO 4 . The concentration of Fe with time agreed with a consecutive first‐order reaction mechanism involving liberation, k 3 , and precipitation, k 4 , of Fe. The rate constants were evaluated by nonlinear regression analysis, and the reaction model represents the data well. The rate constants, k 3 and k 4 , increased with the ratio Fe:P, whereas increasing the initial concentration of KH 2 PO 4 caused k 3 to increase and k 4 to decrease. The precipitate was prepared in 1 M KH 2 PO 4 solution and identified as potassium iron phosphate, K[Fe(OH) 1.33 ] 3 ·(H 2 PO 4 ) 6 ·2H 2 O, by chemical and x‐ray analysis.