Toward a green organic phase: Replacing fossil solvents with vegetable oil in interfacial polymerization

Fossil solvent is replaced with edible vegetable oil in interfacial polymerization. • Soya-bean oil is optimal due to its well film-forming ability and low viscosity. • Soya-bean oil-based NF membrane exhibits thick PA layer with high salt rejection. • Soya-bean oil can act as green substitute for greener TFC membrane production. Despite the prevalent use as organic phase in interfacial polymerization (IP), conventional fossil solvents such as n-hexane are toxic, volatile and flammable, raising growing concerns about their safety. Regarding this issue, hereon we employ edible vegetable oils as a green organic phase to replace fossil solvents for the preparation of thin film composite (TFC) nanofiltration (NF) membranes. Five candidates including soya-bean oil, peanut oil, corn oil, flaxseed oil and olive oil were selected for exploration. Characterization demonstrates that soya-bean oil is the optimal selection, which can be attributed to its superior film-forming ability, low viscosity and facile removability. The selectivity of the soya-bean oil-based TFC NF membrane can be further improved by regulating IP parameters. Compared to the membranes fabricated with n-hexane and Isopar G, the soya-bean oil-based NF membrane exhibits a much thicker polyamide (PA) layer with thickness around 161 nm. This structural characteristic enables excellent desalination performance, with salt rejection exceeding 98% for MgSO 4 and 99% for Na 2 SO 4 . However, the increased thickness also results in a relatively lower water permeability of about 3.5 L m −2  h −1  bar −1 . Our study demonstrates the feasibility of using soya-bean oil as a substitute for conventional fossil solvents in IP reaction. It thereby offers a promising alternative for enabling greener production processes in TFC NF membrane manufacturing. Download: Download high-res image (180KB) Download: Download full-size image