Hydrophilic, oleophilic and switchable Janus mixed matrix membranes for oily wastewater treatment: A review

Purification of oily wastewater holds significant importance due to its detrimental environmental and human health implications. Mixed matrix membranes (MMMs) have gained substantial traction as an efficacious approach for treating oily wastewater, surpassing conventional techniques in terms of performance. To improve the properties of polymeric membranes, scientists have blended them with other polymers or nanomaterials and used various techniques such as phase inversion and electrospinning to prepare MMMs. This review focuses on recent advances in hydrophilic, hydrophobic, and Janus MMMs for oily wastewater treatment. While hydrophilic membranes have exhibited commendable oil rejection capabilities, their susceptibility to fouling remains an issue. Hydrophobic membranes exhibit high fouling resistance but low oil rejection performance. Nonetheless, they demonstrate an excellent ability to separate water-in-oil emulsions. Janus MMMs, which have both hydrophilic and hydrophobic properties, have shown promising results for oily wastewater treatment due to their high oil rejection and fouling resistance. Membrane fouling and recyclability are still the main challenges facing MMMs. To address these challenges, researchers are investigating the use of sustainable and biodegradable polymers in MMMs, which could lead to more environmentally friendly and cost-effective solutions for oily wastewater treatment.