Self-surface heating membrane distillation for sustainable production of freshwater: A state of the art overview

Shortage of freshwater is a global challenge related to population growth, changes in climate conditions and industrial and agricultural needs. Thus, sustainable freshwater production through desalination and wastewater treatment is essential for various human purposes. Membrane distillation (MD) is a recent thermal driven membrane based purification technology with capability to eliminate the limitations of traditional desalination technologies by a synergistic exploitation of the nexus between water and energy. Though MD is recognized as an ecofriendly technology, input heat energy utilization and its efficient management remains a challenge influencing the economic viability of the technology and hindering its realistic applications. To solve this problem, it requires an integrative approach involving materials chemistry, physical chemistry, polymer science, and materials engineering. In addition to the use of robust wetting and fouling resistant membranes, employing the newly developed self-surface heating membranes such as photothermal, joule heating and induction heating membranes have not only minimized energy requirement and fouling issues of MD technology but also enabled it to be considered as potential and economically viable approach for producing high-quality freshwater with negligible carbon footprint. Specifically, recent studies on self-surface heating membranes, utilizing nanomaterials with photothermal, conductive, and magnetic properties, have revealed new possibilities for renewable energy utilization in MD technology. Through direct irradiation or photovoltaic energy conversion, nanomaterial-integrated membranes significantly enhance MD's energy efficiency and productivity without compromising cost-effectiveness, opening avenues for sustainable desalination and water purification technologies. Here, we furnish a comprehensive state of the art overview on (1) the progress of conventional antifouling MD membranes and (2) the opportunities, challenges and limitations of the emerging field of self-surface heated MD (i.e., photothermal MD (PMD), Joule-heating MD and Induction heated MD). We also discuss the exceptional physicochemical properties, antifouling properties, fabrication and scalability of self-surface heating membranes, as well as the strategies for their deployment into MD modules enabling localization of heat at the membrane surface for direct feed heating, thereby leading to sustainable freshwater production.