Use of Micellar-Enhanced Ultrafiltration to Remove Dissolved Organics from Aqueous Streams

Abstract

Abstract Traditional ultrafiltration is ineffective at removing dissolved low molecular weight organics from water. In micellar-enhanced ultrafiltration (MEUF), surfactant is added to the water at concentrations well above the critical micelle concentration. Almost all of the organic originally dissolved (the solute) solubilizes in the micelles formed by the surfactant. The solution then passes through an ultrafiltration membrane with pores small enough to block micelle passage. The permeate contains (at most) only the unsolubilized solute and the surfactant monomer, both at very low concentrations. In this work, the criteria for selecting a surfactant are considered and MEUF is tested on an aqueous stream containing 4-tert-butyl-phenol with hexadecylpyridinium chloride as the surfactant. At high surfactant concentrations (0.25 M) in the retentate, rejections decrease, probably owing to the formation of n-mers (e.g., dimers, trimers, etc.) which are able to pass through the pores along with some solubilized solute. Also under these conditions, the viscosity increases while fluxes decline sharply. So long as these high surfactant concentrations are avoided, MEUF is an extremely effective separation technique, resulting in an average solute rejection of 99.7%, a permeate/feed ratio of 87%, and good fluxes under the conditions studied.