Sustainable and green membranes for chemical separations: A review

Chemical separation technologies such as water purification, gas separation, and solvent recovery have increasingly adopted membrane-based methods for their efficiency and adaptability. However, the cost and environmental consequences of traditional membrane synthesis, including the use of fossil-based polymers and toxic solvents are hindering their scaleup and large-scale adoption. Recognizing this, efforts to replace polymers with sustainable biopolymers and recycle/upcycle waste polymers are underway. Furthermore, the need to replace toxic solvents, such as hexane, with green alternatives, like deep eutectic solvents (DES), is being realized. Although the efficacy of using sustainable alternatives to membrane materials are reviewed in some studies, a comprehensive review that unifies these approaches has been lacking. This review aims to fill this gap by presenting a detailed analysis of sustainable membrane technologies, examining the use of bio-based polymers, green solvents, recycled waste materials, and natural additives. The work emphasizes the vast application potential of these environmentally responsible alternatives across various separation processes and highlights innovative techniques for waste valorization in membrane synthesis. While showcasing prospects, the review also identifies persistent challenges, particularly the dependency on fossil-based inputs. By presenting an integrated perspective on the development and implementation of green membranes, this study is expected to guide future research in the field and contribute to promoting the circular economy and achieving sustainable development goals (SDGs).