Recent Progress, Challenges, and Opportunities of Membrane Distillation for Heavy Metals Removal.

Water is essential for the presence of life on this earth. However, water contamination due to the presence of heavy/toxic metals is one of the serious environmental issues for living beings. Several methods have been devoted to separating or removing those heavy metals from wastewater. Among them, membrane distillation (MD) has become one of the most attractive approaches due to its higher rejection rate than processes driven by pressure, lower energy consumption than traditional distillation processes. MD has gained significant attention for removing heavy metals than other techniques like ion exchange and adsorption in the last two decades. This review provides insight knowledge to the reader and focuses on how heavy metals impact humans and the environment, sources of heavy metals, current and especially removal methods using the MD method. Moreover, recent studies, challenges, and opportunities on MD membrane modules and heavy metal removal systems are discussed. More importantly, in this review, we have identified the gaps and opportunities that are required for enhancing the MD approach and its practical suitability for heavy metal removals. MD module and system showed high performance, proving their possible applications to remove heavy metal ions in water/wastewater treatment.