Membrane distillation technology for molecular separation: A review on the fouling, wetting and transport phenomena

Membrane distillation (MD) is a thermally-driven membrane-based separation technique, which has shown great potential of use for molecular separation in different processes like wastewater treatment and desalination. This technology applies a microporous hydrophobic membrane (MHM) to remove dissolved molecules from a liquid flow. Despite brilliant advantages, use of MD process in industries has been restricted due to the non-existence of sufficient information about membrane types, modules specifications and techno-economic data at full scale. This paper aims to present a comprehensive overview of the advantages of MD process compared to other conventional membrane-based techniques and major operational challenges towards the application of this technique for industrial purposes. Fouling and wetting of membranes are noteworthy challenges, which may prevent the widespread use of the MD process in various industrial approaches such as wastewater treatment. Inappropriate management of both fouling and wetting can eventuate in membrane damage and as a result, decrement of separation efficiency. The prominent objective of this review is to interpret the transport phenomena, different fouling/wetting mechanisms and their suitable mitigation procedures in MD system accompanying with recommending promising strategies that may be beneficial in perceiving and minimizing the fouling/wetting problem.