Large-scale membrane technology has been widely implemented and rapidly growing for roughly 40 years. However, considering its entire life cycle, there are aspects being characterized by low sustainability, and this industry certainly cannot be defined as green. In the membrane manufacturing process, raw materials mainly rely on nonbiodegradable petroleum-based polymers and hazardous solvents. These materials are thus associated with the energy crisis and with disposal burdens at the end of their lifetime, and they pose risks to workers and the environment. Therefore, biobased polymers and green solvents should be employed within the membrane preparation process and replace traditional ones. Moreover, the wastewater generated from membrane fabrication processes contains an important amount of organic solvents and should be efficiently treated or recycled before discharge. The application of artificial intelligence in membrane manufacturing and use processes can also improve efficiency significantly. Finally, a large number of spent membrane elements should also be reused and recovered, rather than landfilled. This review critically evaluates the recent advances in methods to improve the sustainability of membrane technology, specifically emphasizing the progresses made, with regard to the above aspects. This review thus analyzes the needs for membrane industry transformations in the light of circular economy.

Traditional solvents are harmful to human health and the environment. Here, we use a green solvent, dimethyl sulfoxide (DMSO), to replace traditional solvents partly as well as improve membrane performance. The amphiphilic copolymer poly­(vinyl chloride)-graft-poly­(ethylene glycol) methyl ether methacrylate (PVC-g-PEGMA) is blended with PVC to improve the membrane performance. PVC cannot dissolve in DMSO, so based on the Hansen solubility parameter calculation, we investigated the mixture solvents of traditional solvents and DMSO. We found that membranes fabricated by solvent 1-methyl-2-pyrrolidinone (NMP)/N,N-dimethylacetamide (DMAc)/DMSO = 4/3/3 had the highest pure water flux of 891.54 ± 64.41 L m–2 h–1 bar–1 and the highest sodium alginate (SA) rejection of 94.7 ± 1.3%. Other studies have rarely reported modified PVC membranes with such good performance. This membrane was a successful attempt to use a green solvent in membrane fabrication, meeting the challenges of sustainability in chemical enterprises.

Large-scale membrane fabrication currently relies on the use of traditional solvents, such as N,Ndimethylacetamide, 1-methyl-2-pyrrolidinone, and dimethylformamide. These solvents are toxic, slowly biodegradable, and combustible, posing risks to human health and the environment, and requiring careful safety procedures. Replacing traditional solvents with green solvents while maintaining or improving the membrane performance is a challenging task at the forefront of research and development in the field of membrane technology. We employed a novel green solvent, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv PolarClean), to prepare high-performance poly(vinyl chloride) ultrafiltration membranes. This green solvent was used to completely replace toxic solvents during membrane fabrication, for the first time. The effects of polymer concentration, addition of amphiphilic copolymer poly(vinyl chloride)-graf t-poly(ethylene glycol) methyl ether methacrylate concentration, and use of a nonwoven polyethylene terephthalate fabric as support layer were investigated systematically. The membrane fabricated with 8% PVC, 5% PVC-g-PEGMA, and nonwoven PET fabrics as support layer showed the best overall performance, presenting small and narrowly distributed membrane pores, high surface porosity, smooth surface, ultrahigh pure water permeability coefficients of >5000 L m −2 h −1 bar −1 , high sodium alginate rejection of nearly 98%, and flux recovery ratio of 57%. This study demonstrates the feasibility of using green solvent to increase the sustainability and effectiveness of membrane processes.

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