Effect of Ionic Surfactants and Alcohols on the Morphology of CuSO4·5H2O Crystals: Combined Use of Factors and Significance of Threshold Surfactant Concentration

Batch cooling and antisolvent crystallization of copper sulfate pentahydrate using surfactant additives is investigated to understand the effect of various factors on its morphology. It has been found that nonionic surfactants have a marginal effect on this ionic compound, whereas ionic surfactants are able to modify the morphology substantially. Alcoholic antisolvents are also found to be effective habit modifiers that produce elongated crystals. It has been shown that the effects of surfactants and antisolvents can be combined by using a surfactant–antisolvent pair. The effect of surfactant is observed after a certain threshold concentration. A detailed study of the critical micellar concentration (CMC) of sodium dodecyl sulfate in copper sulfate pentahydrate solution confirmed that this threshold concentration is close to the CMC of the surfactant in copper sulfate pentahydrate solution. Evidence suggests that a concentration higher than CMC is required to maintain a surfactant reservoir in the system,...