Membrane surface zwitterionization for an efficient microalgal harvesting: A review

Membrane technology has emerged as a possible solution to the challenge of biomass recovery facing microalgal industry. However, fouling phenomenon hinders the development of membrane processes. In this regard, different fouling mitigation strategies have been developed, among which membrane surface modification is one of the most promising approaches to enhance fouling resistance. Among the surface-active materials that have been explored for membrane antifouling surface modification, zwitterionic materials show superior antifouling properties. This review discusses the unique structural features of zwitterionic materials giving rise to several outstanding properties such as high polarity, anti-polyelectrolyte effect, molecular self-association and super surface hydration which act synergistically to deal with an array of foulants in feed solutions. The foulant dynamics and fouling mechanism in microalgal culture processing are also highlighted and the anti-fouling mechanisms of zwitterionic materials such as physical and steric hindrances are discussed. Membrane zwitterionization approaches are critically outlined and their potential application for effective microalgal culture dewatering is discussed.