Recovery of phenolic compounds from wastewaters through micellar enhanced ultrafiltration

In this research work, the efficiency of Micellar Enhanced Ultrafiltration (MEUF) was evaluated for recovery of polyphenols from aqueous solution, using three surfactants, namely Esterquat, Dodecylbenzenesulfonic acid sodium (DBSS) and Lutensol AO 7 (cationic, anionic and non-ionic surfactants, respectively). Firstly, the critical micellar concentration (CMC) was experimentally determined for each surfactant. CMC values of DBSS was almost 4 orders of magnitude higher than Esterquat and around 200 orders higher than Lutensol A07, indicating the high efficiency of micellization for Esterquat and Lutensol A07. On the other hand, the effect on the polyphenols retention percentage of several factors in the practical application of MEUF was investigated including transmembrane pressure, nature of surfactant, feed surfactant concentration, mole fraction of non-ionic surfactant as well as initial pH value. Results showed that the permeate flux increased with increasing transmembrane pressure. It was concluded that the highest retention efficiency was obtained for the cationic surfactant during the first filtration minutes (higher than 90%). Moreover, the surfactant concentration of 5 CMC gives the best rejection percentage. There was no significant improvement with addition of non-ionic surfactant. Regarding the influence of initial pH, polyphenols rejection percentage slightly increased with an increase in the pH up to a value equal to 3 (from 93 to 95%), but higher pH values resulted in lower polyphenols retention percentage. The results demonstrate the high efficiency of MEUF system under optimal conditions for the treatment of polyphenols-contaminated wastewaters and for the concentration and recovery of these phenolic compounds.