Removal of phenolic compounds by micellar enhanced ultrafiltration using an anionic surfactant

Micellar Enhanced Ultrafiltration (MEUF) of different phenolic derivatives including para-coumaric acid, vanillic acid, and tyrosol, in aqueous solutions has been studied. The MEUF experiments were conducted using an anionic surfactant, namely, Sodium Dodecyl Sulfate (SDS). Two polyethersulfone membranes with different molecular weight cut-off (20 kDa and 50 kDa) were used. Experiments were conducted in a stirred batch cell. The effects of surfactant and solutes concentrations on the permeate flux and on the observed retention have been investigated. The MEUF efficiency was compared to the nanofiltration in terms of flux and rejection. Monovalent and divalent electrolytes were tested for precipitation and recovery of the dodecyl sulfate anion from the retentate stream. The retention of solutes without using any surfactant varies from 1.2 to 6.8% only, whereas, under the same operating conditions, retention increases to about 30 to 67% depending on the nature of solute, the surfactant concentration and the molecular weight cut-off of the membrane. The rise of the surfactant concentration from 5 CMC to 10 CMC increases the phenolic compounds rejection by 15 to 30% only. Our tests demonstrated that the SDS can be removed easily from the retentate by precipitation using CaCl2. The MEUF appears as a promising process for the treatment and valorization of phenolic effluents since it allows higher rejection and reasonable fluxes compared to the nanofiltration which showed a maximum rejection of 40% for vanillic acid and 13% for tyrosol.