Critical review on membrane designs for enhanced flux performance in membrane distillation

Membrane distillation (MD) is a hybrid of thermal and membrane processes that utilizes a hydrophobic mem-brane to separate volatile solutes from feed solution at fairly high temperatures. This process is known to be capable of achieving excellent separation efficiency at low pressure. However, the commercialization of MD has been hampered by low flux performance. To date, different membrane designs have been introduced to ameliorate the flux performance of MD membranes. This article aims to review four key membrane innovations that could enhance the flux performance of MD including the phase inversion-based asymmetric membrane structures, hydrophobic/hydrophilic membrane structures, electrospun nanofibrous membranes (ENMs), and the incorporation of carbon materials. The state-of-the-art of these developments and their recent research trends have been extensively discussed. An update-to-date review of high-flux MD membrane innovations have also been provided. The economic potential of MD membranes is addressed in the final part of this article.