The synergistic effect of orthophosphate and polymer on the precipitation of calcium carbonate

The inhibition properties of polymer acrylic acid/2-acrylamido-2-methylpropanesulfonic acid/2-hydroxypropyl acrylate (AA/AMPS/HPA) and orthophosphate on calcium carbonate precipitation were studied by measuring the induction period and inhibition efficiency. Employing the classical homogeneous nucleation theory, the interfacial tension between calcium carbonate and supersaturated solutions was estimated in the absence and presence of orthophosphate and AA/AMPS/HPA. It was observed that the induction period increased with increasing orthophosphate concentrations up to 5 × 10−5 M and then decreased slightly. The length of induction period increased with increasing AA/AMPS/HPA concentrations up to 20 mg L−1. Good synergistic effects between orthophosphate and AA/AMPS/HPA polymer were obtained. It is therefore possible to assume that orthophosphate and AA/AMPS/HPA are adsorbed on the calcium carbonate crystal and thus yield an obviously elevation of interfacial tension.