The Effect of polymeric additives on calcium sulfate crystallization

ABSTRACT The control of crystal growth and change morphology of crystal is of considerable importance in industrial crystallization. Additives are often used in crystallization processes because they may increase the induction period and effect nucleation behaviour. In this study, the effects of additives on the crystallization of calcium sulfate dihydrate (CaS04.2H20, gypsum) have been investigated in aqueous solutions. Poly(propilen oxide)- block-poly(ethylene oxide) (i.e., PO-b-EO) and poly(methacrylic acid)-block- poly(ethylene oxide) (i.e., MAA-b-EO) copolymers with different molecular weight and acid contents have been used as additives. The effect of polymers on the rate of precipitation of CaSC>4 was determined by recording the decrease of solution conductivity as a function of time. The polymer achitecture, acid content and molecular weight of the polymers were found to be the most important parameters in inhibition of calcium sulfate dihydrate crystallization.