Hexavalent chromium ion removal through micellar enhanced ultrafiltration

Micellar enhanced ultrafiltration (MEUF) experiments were carried out in an unstirred batch cell using cetyl pyridinium chloride (CPC) as the surfactant to analyze the adsorption of chromate ions on the surfaces of the surfactant micelles. The influence of independent variables was studied on the retention of the surfactant and chromate ions as well as on permeating flux. The flux, for a particular pressure, remained constant against constant bulk concentration of CPC, suggesting negligible concentration polarization in the range of feed surfactant concentrations considered herein. There was distinct evidence of adsorption of Cr(VI) ions during MEUF. The Langmuir adsorption equilibrium constant (Kads) for chromate ions was found out with the help of MEUF results. It was observed that at high feed concentration, the percent retention of chromate ions increases. However, the flux declined over a varying range of feed concentration (CPC and chromate ions). Further, at a much higher surfactant concentration (60 mM), the retention of chromate ions slightly decreased. The exclusive experimental runs with chromium ion solution showed an initial rapid decline of retention from 10 to 2.3% with increase in pressure.