Applications of electrically conductive membranes in water treatment via membrane distillation: Joule heating, membrane fouling/scaling/wetting mitigation and monitoring

Membrane distillation (MD) is a thermally driven separation process that is driven by phase change. The core of this technology is the hydrophobic microporous membrane that prevents mass transfer of the liquid while allowing the vapor phase to pass through the membrane's pores. Currently, MD is challenged by its high energy consumption and membrane degradation due to fouling, scaling and wetting. The use of electrically conductive membranes (ECMs) is a promising alternative method to overcome these challenges by inducing localized Joule heating, as well as mitigating and monitoring membrane fouling/scaling/wetting. The objective of this review is to consolidate recent advances in ECMs from the standpoint of conductive materials, membrane fabrication methodologies, and applications in MD processes. First, the mechanisms of ECMs-based MD processes are reviewed. Then the current trends in conductive materials and membrane fabrication methods are discussed. Thereafter, a comprehensive review of ECMs in MD applications is presented in terms of the different processes using Joule heating and various works related to membrane fouling, scaling, and wetting control and monitoring. Key insights in terms of energy consumption, economic viability and scalability are furnished to provide readers with a holistic perspective of the ECMs potential to achieve better performances and higher efficiencies in MD. Finally, we illustrate our perspectives on the innovative methods to address current challenges and provide insights for advancing new ECMs designs. Overall, this review sums up the current status of ECMs, looking at the wide range of conductive materials and array of fabrication methods used thus far, and putting into perspective strategies to deliver a more competitive ECMs-based MD process in water treatment.