Simultaneous removal of organic and inorganic contaminants by micellar enhanced ultrafiltration with mixed surfactants

Abstract

Micellar-enhanced ultrafiltration (MEUF) is a promising technology to separate organic and inorganic contaminants simultaneously under mild conditions. Above a critical micelle concentration (CMC), surfactants form a micelle which is a spherical aggregate of 50-150 surfactant molecules. Organic compounds are solubilized into the core of micelle and inorganic pollutants can be bound on the surface of oppositely charged micelle. Trichloroethylene (TCE) and chromate were selected as organic and inorganic contaminants, respectively. In this study, the mixed surfactants were used to minimize the permeate surfactant concentration and enhance solubilization capacity. Cetylpyridinium chloride (CPC) as a cationic surfactant and Tween 80 as a nonionic surfactant were used to form surfactant mixed micelles. The selection of appropriate surfactant and the effective ratio of concentration between surfactant and target pollutant were essential factors in MEUF system. A batch solubilization test was carried out to select the nonionic surfactant as a solubilizing agent. The solubilization of TCE was influenced by the surfactant structure, i.e. hydrophile-lipophile balance and carbon chain number. The optimum surfactant concentration for TCE solubilization was also investigated. In the removal of chromate, the electrostatic binding efficiency with CPC (cationic surfactant) was observed through the MEUF test with various surfactant concentrations to find out the optimum CPC concentration. The MEUF process for removal of single pollutant with the mixed surfactant solution was performed to investigate the effect of the mixed surfactant system. The CPC rejection was enhanced by addition of Tween 80, which is mainly attributed to the decrease in CMC. The removal efficiency of chromate was also lower than that of single CPC system. These results were ensured from the decrease of zeta potential in the mixed surfactant system compared to single CPC system, occurring due to the reduct...