Zwitterionic M-PhA modified GO nanocomposite membranes for enhanced organic solvent nanofiltration and wastewater treatment with antifouling performance

Graphene oxide (GO) has recently been used for wastewater treatment and organic solvent nanofiltration (OSN) applications due to its unparalleled combination of atomic-level thickness, tunable pore size, and high surface area, which enable efficient molecular sieving and selective transport for many solvents. However, its practical wastewater treatment and OSN separation performance are limited owing to small d-spacing and trade-off between permeability and selectivity owing to the swelling effects in harsh environments. To address these challenges, we have developed novel zwitterionic M-PhA complex-modified GO nanocomposite membranes. Notably, GO-M-PhA nanocomposite membranes achieved superior separation, effectively removing herbicides and dyes from wastewater and organic solvents, with higher solvent permeance than pristine GO membranes. The optimized GO-M-PhA-30 membrane achieved high rejection rates of 99.96 % for cationic methyl green (MG) dye with an ethanol permeance of 13.98 L m⁻² h⁻¹ bar⁻¹, 99.97 % for anionic Congo red (CR) dye with an ethanol permeance of 13.23 L m⁻² h⁻¹ bar⁻¹, and 99.43 % for pendimethalin (PM) pesticide, while maintaining a water permeance of 18.98 L m⁻² h⁻¹ bar⁻¹. The optimized nanocomposite membrane effectively rejected CR (≥98 %) in various organic solvents. Furthermore, the GO-M-PhA membrane exhibited outstanding durability during pressure-driven separation of MG in ethanol, maintaining stable nanofiltration performance over a continuous period of three days. Throughout this duration, the rejection rates for MG remained nearly constant, highlighting the membrane's superior mechanical strength and chemical stability. Additionally, the optimum GO-M-PhA-30 nanocomposite membrane exhibited a strong resistance to fouling compared to the pristine GO membrane. Compared to other GO-based nanocomposite membranes, these findings underscore the remarkable potential of the GO-M-PhA membrane for practical wastewater treatment and OSN applications.