The precipitation of ferric phosphate on porous polymer

Abstract

Polymers with high porosity may be appropriate substrates for the deposition of inorganic salts. Thus the commercially available Porapak N was found to be an appropriate substrate for the deposition of an acidic iron phosphate crystalline phase at 25°C and pH 2.00. The stoichiometry of this acidic ferric phosphate polymorph according to the chemical analysis and spectroscopic results was found to be Fe 2(HPO 4) 3 and its thermodynamic solubility product was found to be 8.6×10 −41 at 25°C. In all cases, a well-defined induction period preceded the onset of acidic ferric phosphate overgrowth, reflecting the time required for the formation of the critical nucleus. The induction times were inversely proportional to the solution supersaturation while the rates of the concomitant crystal growth increased with supersaturation with an apparent order of 1.