Development of a PDMS-grafted alumina membrane and its evaluation as solvent resistant nanofiltration membrane

•A method is described to tune the pore size and the surface chemistry of ceramic membranes.•A hydrophobic solvent resistant membrane is developed by grafting a PDMS layer on a ceramic γ-alumina membrane.•Reproducible and long-term stable flux values were obtained for toluene, n-hexane and iso-propyl alcohol.•Nanofiltration with Molecular Weight Cut Off (MWCO) values of 500 DA was achieved.

A new solvent resistant nanofiltration (SRNF) membrane is developed by grafting a PDMS polymer into the pores of a 5 nm γ-alumina ceramic membrane. These PDMS-grafted γ-alumina membranes were attained through a two-step synthesis. The linking agent, 3-aminopropyltriethoxysilane (APTES), was first applied on a ceramic membrane either by a vapor phase or a solution phase method, followed by grafting of an epoxy-terminated PDMS. Through this route it was possible to tune the pore size and to engineer the surface chemistry (e.g. hydrophobicity) of ceramic membranes in favor of non-polar organic solvent permeation. Reproducible results were obtained for filtration experiments with hexane, toluene and isopropanol (IPA). As expected, higher permeabilities were found for non-polar solvents than for more polar solvents (resp. 4.8±0.1 l m−2 h−1 bar−1 for hexane, 3.1±0.5 l m−2 h−1 bar−1 for toluene and 0.54±0.04 l m−2 h−1 bar−1 for IPA). A Molecular Weight Cut Off (MWCO) of 500±10 Da was determined. Stability tests in hexane, toluene and IPA have shown that these newly developed membranes were stable in all these solvents during testing periods of up to 170 days.