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Polymeric membranes are important in advanced separation technologies because of their high efficiency and low environmental impact. However, procedures for membrane production are far from sustainable and environmentally friendly. This work presents a life cycle assessment of the environmental impact of fabricating 1000 m2 of hollow fiber polymeric membranes. Membrane materials considered include the most popular fossil- and bio-based polymers in current use, i.e., polysulfones, polyvinylidene fluoride, and cellulose acetate. Solvents considered for use in polymer dope solution included polar aprotic solvents (N-Methyl-2-pyrrolidone, N, N-dimethylacetamide, and dimethylformamide) that are widely used in industry and an alternative green solvent (ethylene carbonate). The impacts of membrane production on global warming, marine ecotoxicity, human carcinogenic and non-carcinogenic toxicity, land use potential, and fossil resource scarcity were analyzed. Additionally, the impact on the sustainability and environmental cost of membrane production resulting from replacing fossil-based polymers with bio-based polymers or substituting toxic solvents with a green alternative was investigated. Hot spots in the membrane production process were identified, and measures to reduce the environmental impact of membrane production were proposed.

The use of highly toxic solvents presents significant risks to both the environment and human health. Therefore, the adoption of green solvents will be crucial for achieving sustainable membrane production. This work reports the use of inexpensive environmentally friendly biobased and biodegradable cyclic carbonate solvents, namely ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), to fabricate polyvinylidene fluoride (PVDF) membranes. The solvent dependence of the phase inversion mechanisms, morphology, crystalline structures, and polymorphism of the prepared PVDF membranes were investigated. Polymorph analysis revealed that membrane fabrication in EC or PC yielded exclusively the β-phase product, whereas PVDF membrane fabrication in BC yielded a mixture of α and β phase material. The mechanism of β-phase formation was investigated using molecular dynamics simulation and shown to depend on the extent of hydrogen bonding at the polymer–solvent interface. The PVDF membrane formed in EC exhibited the highest porosity and pure water permeability, and was therefore tested in direct contact membrane distillation (DCMD), exhibiting promising results in terms of permeate flux and salt rejection. These results suggest that large-scale production of piezoelectric PVDF membranes using green solvents should be practically feasible.

Deep eutectic solvents (DES) have recently emerged as a new class of inexpensive biodegradable solvents and additives with diverse applications. In this study, a new family of non-ionic deep eutectic solvents (NIDES) is proposed for the first time for membrane preparation. Three types of NIDES, N-methylacetamide-acetamide (DES-1), N-methyl acetamide-N-methyl urea (DES-2), and N-methyl acetamide-N,N′-dimethyl urea (DES-3) were synthesized and used to dissolve polyvinylidene fluoride (PVDF) polymer. The effects of the additive polyvinylpyrrolidone (PVP) and the type of NIDES on the PVDF membrane characteristics, water permeability and bovine serum albumin (BSA) separation were studied. The membranes prepared with DES-1 and 2 wt% PVP exhibited a good water permeate flux (96.82 L/m2.h) and a high BSA separation factor (96.32%). High performance PVDF membranes can thus be efficiently prepared using biodegradable inexpensive NIDES.

Solvent toxicity is a major barrier to sustainable fabrication of polymeric membranes. This study introduces three dibasic esters (DBEs) as alternative membrane fabrication solvents that are biodegradable, non-carcinogenic, non-corrosive, and non-hazardous. The use of DBEs in fabrication processes shifts the monotectic point in the phase diagram of PVDF/solvent systems towards higher polymer concentrations, enabling membrane formation by liquid–liquid phase inversion to produce a bicontinuous structure that confers outstanding performance. The best-performing membrane prepared in this way had an exceptional flux of 42.40 kg m⁻² h⁻¹ and a high rejection rate (>99%) in the decontamination of synthetic nuclear wastewater. Compared to membranes prepared previously using toxic and non-toxic solvents, membranes fabricated in DBEs exhibited superior mechanical performance due to their bicontinuous structure, which effectively distributes external forces throughout the membrane. Moreover, DBEs are cheaper than toxic conventional solvents and are readily available in bulk, making them attractive options for industrial-scale membrane production.