Influence of different solvent and time of pre-treatment on commercial polymeric ultrafiltration membranes applied to non-aqueous solvent permeation

Abstract Several pre-treatments and solvents were tested through permeation in commercial polymeric membranes (UH004, UP005, UP010 and UH050 – Microdyn-Nadir) with different molar mass cut-offs (4 kDa, 5 kDa, 10 kDa and 50 kDa, respectively), in order to evaluate their efficiency and stability through non-aqueous solvent permeation. After pre-treatments and permeations, membranes were characterised with contact angle, Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electronic Microscopy (FESEM) to evaluate structural integrity. The results of solvent permeation suggest that selectivity of the polymeric matrix depends not only on pore size, but also, in great extent, on the interaction between solvent and polymer. A strong relation can be noted between the conditioning length and permeability for ethanol pre-treatments. Permeability to n -hexane increased from 4 to 18 times after pre-treatment, depending on the time of exposure to ethanol and n -hexane. Characterisation analyses show no significant changes on the membranes surface. In some cases, discrepancies observed among permeate fluxes and contact angles might be an indicative of the occurrence of swelling and plasticisation. However, results suggest the feasibility in the use of these membranes for the recovery of solvents in the oil industry, if suitable process parameters are chosen.