Industrial & Engineering Chemistry Research, Vol.52, No.43, 15041-15048, 2013
Effect of Ionic Surfactants and Alcohols on the Morphology of CuSO4 center dot 5H(2)O 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, leading to a change in the crystal morphology. This insight may help to predict the minimum required surfactant concentration for habit modification for an unknown system.