Removal of phenol and substituted phenols by newly developed emulsion liquid membrane process

Emulsion liquid membrane (ELM) stabilized by non-Newtonian conversion of the liquid membrane phase and dispersed in a Taylor–Couette flow was applied to treat model industrial wastewaters containing phenols and selected substituted phenols (hydroquinone, three chlorophenols and two nitrophenols) at relatively high concentrations. Under optimized operating conditions, all the compounds except hydroquinone were extracted with the maximum extraction efficiency of over 96% and the time to reach maximum extraction ranged from 2 to 30 min. For 2-chlorophenol, 2,4-dichlorophenol, and 2-nitrophenol, maximum extraction efficiency of over 99% was reached in less than 2 min of contact time. Extraction of these compounds from the mixture was also highly efficient. Factors that affected the overall extraction efficiency such as acid-base speciation of the target compounds and the affinity between the target compounds and the membrane phase were determined. This study suggested that the newly developed ELM process might provide a promising alternative technology to treat industrial wastewaters containing high concentrations of phenolic compounds.