Application of vacuum membrane distillation for concentration of organic solutions

Vacuum membrane distillation was used to concentrate organic solutions containing mainly 1,3-propanediol, ethanol and carboxylic acids. The studied solutions were permeates obtained from nanofiltration process applied for the separation of broths from the fermentation of glycerol with the Citrobacter freundii bacteria. The presence of organic solutes decreased the surface tension of permeates to the value of 47 mN m(-1). However, the pores inside the used polypropylene membranes were not wetted by the post-fermentation solutions, and they were concentrated to over five-fold. It was shown that vacuum membrane distillation has over twice higher thermal efficiency compared to that obtained by direct contact membrane distillation. (C) 2016 Institute of Chemistry, Slovak Academy of Sciences