Effect of Aqueous Ammonia on Freeze Drying of Frozen Droplets Difficult to Sublimate

Abstract

Freeze dry processing of certain salt solutions is difficult because of their tendency to melt during drying operation. In this paper, the use of aqueous ammonia was investigated for making freeze-dried particles from such a solution of iron (III) sulfate, which forms frozen droplets difficult to sublimate. Aqueous ammonia promoted the phase separation by making cluster ions and prevented the formation of glassy state in the frozen droplets. By an optimum addition of aqueous ammonia, perfect dried particles were obtained.