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This article in SSSAJ

  1. Vol. 47 No. 3, p. 448-454
    Received: June 25, 1982
    Accepted: Dec 15, 1982

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Fixation Kinetics in Potassium-Aluminum-Orthophosphate Systems1

  1. Y. K. Kim2,
  2. E. L. Gurney3 and
  3. J. D. Hatfield3



The rate of removal of phosphate and potassium from solution was studied by contacting an aluminum-impregnated, cation exchange resin with solutions of monopotassium phosphate in concentrations of 0.05 to 0.25M and with atomic ratios Al:P from 0.25 to 4.0. The removal of both K and P from solution followed first-order reaction models for all experimental conditions, the K being removed faster than the P. The rate constants for K and P removal increased as the ratio Al:P increased, but were affected to a lesser extent by the initial concentration of KH2PO4. The concentration of Al with time agreed with a consecutive first-order reaction model involving cation exchange and precipitation. The rate constants for each experimental condition were evaluated by nonlinear regression analysis, and the reaction model represents the data well. The precipitate (prepared in 0.25 or 1M KH2PO4 solution) was identified as potassium aluminum taranakite by chemical and x-ray analysis. The phosphate retained in the resin was negligibly small and perhaps was occluded in the beads. Phosphate was removed from solution by the precipitation of taranakite. The taranakite precipitation rate constant, k4, varied directly with the atomic ratio Al:P and inversely with the initial KH2PO4 concentration, Co, by the correlation k4 = 1.09 (Al:P)1.066 (Co)-0.401.

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