Green solvents in membrane separation: progress, challenges, and future perspectives for sustainable industrial applications

Green chemistry and engineering play a vital role in sustainable separation and technology developments. Over the past decade, significant progress has been made in applying green solvents to separation processes, with a focus on reducing the reliance on conventional toxic solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc). Green solvents offer a promising alternative due to their biodegradability, low environmental impact, and minimal health hazards. Nevertheless, most existing studies focus on individual solvents or specific applications, leaving gaps in understanding regarding solvent–polymer compatibility, scalability, and trade-offs between sustainability and separation efficiency, particularly for liquid and gas separations in membrane technology. This review addresses these gaps by categorizing recent advancements in the use of green solvents for membrane fabrication over the past decade. The solvents are grouped into the categories esters, polar aprotic, dipolar aprotic, polar protic, non-polar aprotic, organic salts, and oils. These green solvents include γ-valerolactone (GVL), Cyrene™, Tamisolve® NxG, Rhodiasolv® PolarClean, ionic liquids (ILs), deep eutectic solvents (DESs), and plant-derived oils. This review also evaluates the interactions between these solvents and commonly used polymers using the Hansen solubility parameter (HSP), alongside the CO₂ capture and water purification performance of the resulting membranes. Additionally, current applications of artificial intelligence (AI) tools in solvent selection are discussed, highlighting their potential to predict polymer–solvent compatibility and optimize membrane fabrication formulations. By summarizing recent advancements, evaluating industrial applicability, and identifying unresolved challenges, this review provides a roadmap for the adoption of green solvents in next-generation membrane technologies, urging researchers and industry stakeholders to accelerate the transition toward sustainable solvent-based processes.