Double-Hydrophilic Block Copolymers as Precipitation Inhibitors for Calcium Phosphate and Iron(III)

Abstract

Novel double-hydrophilic block copolymers, maleic anhydride (MA)−allylpolyethoxy carboxylate (APEC) and maleic anhydride (MA)−ammonium allylpolyethoxy sulfate (APES), were specially designed and synthesized from allyloxy polyethoxy ether (APEO) to inhibit the precipitation of calcium phosphate and iron (III). Structures of APEO, APEC, MA−APEC, APES, and MA−APES were characterized by FT-IR. The study shows that both MA−APEC and MA−APES have significant ability to inhibit the precipitation of calcium phosphate at the dosage of 6 mg/L, approximately showing 99 and 90% inhibition, respectively. The data of the light transmittance of ferrous solutions show that, compared to MA−APES, MA−APEC has superior ability to stabilize iron (III) in solutions. The light transmittance of ferrous solutions is about 23% in the presence of MA−APEC when the dosage is 6 mg/L, whereas in the presence of MA−APES, it is about 31% at a dosage of 12 mg/L. Scanning electron microscopy (SEM) shows that the copolymers influence the morphology of calcium phosphate crystallites. Transmission electron microscopy (TEM) indicates the excellent inhibition results from the formation of core−shell structure. Double-hydrophilic block copolymers of MA−APEC and MA−APES have also been proven to be effective inhibitors of calcium phosphate and iron (III) even at elevated solution temperature, pH, and Ca2+ and Fe2+ concentration.