Ferric phosphate precipitation in aqueous media

The precipitation and dissolution processes of the iron phosphate system ma y be of particular interest for the mechanism of phosphorus binding in the soils. The system of Fe(NO3)(3)-H-3 PO4-H2O was investigated at pH 2.00 and 25 degrees C. At high supersaturations a crystalline phase of the Formula Fe(H2PO4)(HPO4) . xH(2)O forms spontaneously at rates strongly dependent on the solution supersaturation. The solubility product of the spontaneously precipitating phase was found. Seeding of stable supersaturated solutions w ith the spontaneously precipitating solid resulted in ferric phosphate dihy drate overgrowth, with a second-order dependence of the rate on the relativ e solution supersaturation, suggesting a surface diffusion - controlled mec hanism. (C) 2000 Elsevier Science B.V. All rights reserved.