Preparation of calcium sulfate whiskers using waste calcium chloride by reactive crystallization

Calcium sulfate whiskers, owing to its good thermal stability, chemical resistance and good compatibility with rubber and plastics, has a strong potential in the application of polymer reinforcing composite materials. This work deals with the preparation of calcium chloride whiskers by reactive crystallization process with sulfuric acid and calcium chloride discharged from Solvay process. Firstly, the orthogonal experiments were carried out using both CaCl2 and H2SO4 in analytic grade as feedstock, and the reactive crystallization conditions were optimized, which included reaction temperature, reactant concentration, reaction time and stirring speed. Based on the optimized reactive crystallization conditions, the new process for the preparation of calcium chloride whiskers was studied using the reactive crystallization process with sulfuric acid and calcium chloride discharged from Solvay process, and the effects of impurity ions in the waste solutions on the growth of whiskers were evaluated. It was found that calcium sulfate whiskers with stable and structured fine crystals (its aspect ratio up to 190) can be prepared using waste CaCl2 in Solvay process. The experimental results will provide the valuable information for the reasonable disposal of waste CaCl2 solution from Solvay process. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim