Effects of some parameters affecting the crystallization rate of calcium sulfate dihydrate in sodium chloride solution

Crystallization of calcium sulfate dihydrate (CaSO4.2H2O) in sodium chloride solutions at different supersaturation (δ = 1.2–2), pH =3, ionic strength (I = 0.5 M) and at 80°C was studied. The influence of aluminum and magnesium nitrates having very low concentrations (10 mol dm) on the rate of crystallization at different supersaturation was investigated. The rate of crystallization was found to be dependent of the stirring rate suggesting diffusion mechanism. The addition of Mg or Al retarded the rate of crystallization to an extent proportional to their amounts present. Furthermore, the retardation effect was enhanced as the supersaturation decreases. The results also revealed that the increase in both pH (3 −10) and crystallization temperature (20 −80 C) brought about an increase in calcium sulfate crystallization rate. [ N. S. Yehia, M. M. Ali, K. M. Kandil and M. M. El-Maadawy. Effects of some parameters affecting the crystallization rate of calcium sulfate dihydrate in sodium chloride solution. Journal of American Science. 2011;7(6):635-644]. (ISSN:1545-0740). http://www.americanscience.org