Comparative sorption properties of metal(III) phosphates

Sorption behavior of metal(III) phosphates toward Zn2+ was investigated usi ng different concentrations, pHs, and temperatures. Ion exchange between pr otons from the surface and metal cations from solutions was found to be res ponsible for metal sorption by metal(III) phosphates. Dissociation constant s of metal(III) phosphates and binding constants of the Zn2+ with metal(III ) phosphates were determined using Henderson-Hasselbach and modified Langmu ir equations, respectively. The sorption process in all the three metal pho sphates was found tc, be endothermic in nature while the dissociation proce ss was observed to be endothermic in AlPO4 and FePO4 and exothermic in CrPO 4. (C) 1999 Academic Press.