Process efficacy and novelty of titania membrane prepared by polymeric sol–gel method in removal of chromium(VI) by surfactant enhanced microfiltration

Abstract

Micellar enhanced microfiltration (MEMF), a surfactant-based separation process, is promising in removing multivalent metal ions from aqueous solutions. The choice of the membrane is very important in this process. MEMF of chromium(VI) from aqueous solution was studied using cetylpyridinium chloride (CPC) as the cationic surfactant. A simple preparation method for the porous ceramic membrane was developed from nanocrystalline titania (TiO₂) powder using polymeric sol–gel process. Further the titania membrane from the powder was sintered at 450 °C for 1 h to obtain a stable structure. The membrane morphology and the crystal structure were analyzed by SEM and XRD. The effect of calcination temperature on membrane porosity was also investigated using mercury porosimetry. The mean pore size, porosity and pure water permeability of membrane were 0.58 μm, 0.32 and 1049 l/(m² h bar), respectively. These membranes were used in a batch microfiltration system for removal of hexavalent chromium from aqueous solution. Effects of various parameters such as pH, pressure and surfactant to chromate ratio (CPC/Cr) on microfiltration performance were studied. The removal of chromium(VI) was found to be highly dependent on pH of the feed solution. The surfactant to chromate ratio (CPC/Cr) of 2.5 which was below the CMC was found to be ideal for 99% removal of chromium(VI) at initial chromate concentration 100 mg/l. Titania membranes can be effectively used for treatment of chromium containing wastewaters as an alternative. The membrane synthesis and its use in chromate removal are new findings. Other ions can be effectively removed by titania membranes through proper synthetic processes.