Molecular separation using poly (styrene-co-maleic anhydride) grafted to γ-alumina

Abstract

Here, we report the covalent coupling of poly (styrene-co-maleic anhydride) onto γ-alumina to develop high-performance organic solvent nanofiltration (OSN) membranes. A high molecular weight (M
_w
) alternating copolymer of maleic anhydride (MA) and styrene (St) was synthesized and directly grafted to the γ-alumina membrane, while commercially available low M
_w
random copolymers of St and MA were also investigated. We show that solute rejection and membrane permeability strongly depend on the nature of the applied copolymer. In particular, the M
_w
of the copolymer applied is potentially the key for improving the membrane performance. When a high M
_w
copolymer was applied, the grafted layer covered the surface of the membrane. This results in membranes with significantly improved rejection, while maintaining a high permeability. In contrast, we observed pore grafting by applying low M
_w
copolymers, which resulted in membranes with slightly higher rejection and dramatically lower permeability compared to unmodified membrane. The best results were obtained by grafting γ-alumina with a high M
_w
alternating copolymer. These membranes showed a solute rejection of 98% for Sudan Black B (457 g mol
⁻¹
) in toluene, while the permeability remained high at 2.9 L m
⁻²
h
⁻¹
bar
⁻¹
.