Crystal formation of BaCl2 and NH4Cl using a supercritical fluid antisolvent

The supercritical antisolvent (SAS) process has been used to produce crystals of barium chloride (BaCl2) and ammonium chloride (NH4Cl) from solutions of dimethyl sulfoxide (DMSO). Crystallization was performed by introducing carbon dioxide into the DMSO solutions at different injection rates. Variations in crystal properties such as particle size, crystal habit, and internal space lattice were observed in the SAS processed crystals. The average particle size of the crystals decreased with increasing carbon dioxide injection rate for both compounds. As the injection rate increased, the crystal habit of BaCl2 was modified from an equant to an acicular habit, and that of NH4Cl changed from an equant to a tabular habit. X-ray diffraction patterns showed the transition of the space lattice of BaCl2 from the orthorhombic to hexagonal crystal system. The use of the SAS process for the separation of BaCl2 and NH4Cl mixtures in DMSO was also investigated.