Water and wastewater treatment by micellar enhanced ultrafiltration – A critical review

Micellar-enhanced ultrafiltration (MEUF) is a surfactant-based method used to remove low concentrations of contaminants from water and wastewater streams. The process consists of adding surfactant above the critical micelle concentration (CMC) in the contaminated water to solubilize the contaminant in micelles or to retain ionic contaminants via electro-static interaction with ionic micelles. The micelles size should be enough to be retained in a membrane with larger pore size than the one needed for the retention of the contaminant only. This approach allows the increase of the permeate flux. The parameters that influence MEUF, such as surfactant types, membranes, transmembrane pressure, pH, temperature and ionic strength, are summarized in this work. The literature review is focused on the different uses of MEUF in function of the compound to be removed and a comparison of the different methodologies was elaborated. The recent patents linked to MEUF are also presented. A critical analysis of the reviewed data indicated the most frequent gaps in MEUF studies such as the lack of information regarding important parameters including pH, temperature and permeate flux. It was also observed that inaccurate conclusions are commonly associated with imprecise measurements of CMC. The main challenge for future industrial-scale applications of MEUF is to develop studies from the present simple synthetic wastewater in laboratory-scale to industrial wastewater on a MEUF pilot scale. However, this review article shows the versatility of MEUF as a promising method to remove different types of contaminants from water and wastewater streams, and the future challenges to overcome.