Crystallization Kinetics and Mechanisms of Calcium Sulfate Dihydrate: Experimental Investigation and Theoretical Analysis

In this work, four influencing factors including temperature, stirring speed, pH value, and polymer concentration were chosen to investigate crystallization kinetics of calcium sulfate dihydrate (CSD). At the same time, the chemical-potential-gradient models combined with the extended Debye-Huckel model were used to explore the growth mechanism of CSD and predict the crystal growth kinetics under different external conditions. The results indicated that temperature was the key influencing factor because of the sensitivity of the rate constant k(t) and driving force Delta mu to temperature changes. Moreover, the pH nearly has little effect on them, while the stirring speed and polymer concentration primarily affected k(t) and Delta mu, respectively. On the other hand, the theoretical models indicated that the crystallization mechanism of CSD belonged to the adhesive-type growth mechanism. Moreover, the CSD crystal growth kinetics was well predicted at different temperatures, pH values, and polymer concentrations. Unfortunately, the crystallization kinetics of CSD under different stirring speeds cannot be accurately predicted. The detailed information, such as the key influencing factor and the crystallization mechanism, could provide a reference for the removal of scale in industrial production.