New frontiers in sustainable membrane preparation: Cyrene(TM) as green bioderived solvent

In this work, Cyrene(TM) was employed for the first time as solvent for polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) membrane preparation via phase inversion. The two selected polymers are among the most required materials in the industrial membrane field. PES and PVDF membranes were prepared by coupling Vapour Induced- and Non-solvent Induced Phase Separation (VIPS and NIPS, respectively) with the aim to study the influence of the adopted operational conditions on the final membrane structure and properties. By changing the exposure time to fixed atmospheric relative humidity (55%) and temperature (25 °C) in the range between 0 and 5 min, membranes with different features, pore size and pure water permeability (PWP) could be tailored. The experimental data were discussed with respect to the casting solution viscosity, ternary phase diagram, membrane morphology, thickness, porosity, contact angle, pore size and PWP. In the case of PVDF, additional differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis were performed for evaluating the polymorphism and crystallinity change of the material, which influences the membrane properties too. By working in complete absence of additives and at room temperature, the combinations PES/Cyrene(TM) and PVDF/Cyrene(TM) allowed to develop a new sustainable approach of producing membranes for potential application in water treatment.