Treatment of the Wastewater Containing Cd2+ Using Micellar Enhanced Ultrafiltration Combined with Foam Fractionation

Micellar-enhanced ultrafiltration (MEUF) is a potential tool for the removal of heavy metal ions from wastewater. Permeate of MEUF contains surfactant and small amounts of metal ions which cannot be retained by the membrane. This will raise substantial expense for separation because surfactant cost accounts for a large portion of operational costs, and surfactant makes the effluent from the process environmentally unacceptable. The purpose of this study was to adopt the combined technique of MEUF and foam fractionation (FF) to treat the wastewater contaminated with cadmium (Cd2+) by using anionic surfactant sodium dodecyl sulfate (SDS) at low critical micelle concentrations (CMC) (0.2xCMC-0.9xCMC), and to investigate the influence of MEUF-FF on separation efficiency. The results showed that MEUF combined with FF could enhance the separation efficiency of Cd2+ markedly and decrease the concentration of SDS in the effluent. Compared with the single-MEUF, the combined technique of MEUF-FF could reduce the amount of SDS consumption significantly. The concentration of Cd2+ in the effluent of MEUF-FF was lower than 0.1 mg/L at SDS concentrations of 0.25xCMC, 0.3xCMC, 0.45xCMC, 0.65xCMC, 0.9xCMC, and initial Cd2+ concentrations of 50, 75, 100, 125, and 150 mg/L, respectively. The combined technique of MEUF-FF could be widely used to treat wastewater containing heavy metal ions.