Removal of Organic Acids from Effluent via Freeze Crystallization

Freeze crystallization is an efficient separation process that can potentially be used in any application. Freeze crystallization is a high energy efficiency separation process that can be applied to a wide variety of industrial requirements. Although the vapor-liquid equilibrium is generally employed to separate the components of a solution, use of solid-liquid equilibrium should be considered ? it may be cheaper. This paper describes a case study of recovery of acetic acid from effluent via freeze crystallization. Complete recovery of acetic acid from acetic acid-water solution by ordinary distillation is nearly impossible, because relative volatility of this mixture in the range of 1-30% of acetic acid in water is very close to one. Also, recovery of formic acid from its effluent stream by distillation is not economical viable as effluent stream of formic acid contains only 1-2% of formic acid. But the same separations are possible by freeze separation technique and it is found experimentally that large amount of acetic acid (about 70%) and formic acid (about 90%) can be recovered via freeze separation technique. Also it is found that the energy required for recovery of acetic acid is much lower (about 24 times) than that of distillation.