A hydrophilic cellulose acetate-graft-(glycidylmethacrylate-g-polyethylene glycol) (CA-g-(GMA-g-PEG)) was synthesized and incorporated into acetylated methyl cellulose (AMC) to prepare antifouling ultrafiltration membranes. The successful synthesis of CA-g-(GMA-g-PEG) was confirmed by ¹H-NMR and X-ray photoelectron spectroscopy studies. The AMC blend membranes were characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and contact angle analysis to investigate the effect of CA-g-(GMA-g-PEG) on the properties of the membrane surface. The increase of CA-g-(GMA-g-PEG) content in the AMC matrix reduced the macrovoids and transformed to a sponge-like structure in the entire membrane cross section. Furthermore, the increase in the graft moiety enhanced the performance of the membranes. Surface free energy parameters calculated from the contact angle measurements indicate that the interfacial free energy of the blend membranes were lower than those of the pure AMC membranes. The modified membrane surface became more hydrophilic and more wettable because of the preferential orientation of these polar groups towards the membrane surface. The efficiency of these membranes in the separation of singlet foulants and multi foulants increased significantly, thus increasing the fouling resistance. These membranes would be useful for organic fouling prevention during water and wastewater treatment.

In this study, we present a facile surface modification method using green solvents for a commercial polyimide (PI) nanofiltration membrane to exhibit good acid stability. To enhance acid stability, the PI organic solvent nanofiltration membrane was modified using Fenton’s reaction, an oxidative cross-linking process, using environmentally friendly solvents: water and ethanol. The surface properties of the pristine and modified PI membranes were investigated and compared using various analytical tools. We studied the surface morphology using scanning electron microscopy, performed elemental analysis using X-ray photoelectron spectroscopy, investigated chemical bonds using attenuated total reflectance-Fourier transform infrared spectroscopy, and studied thermal stability using thermogravimetric analysis. The acid resistances of the pristine and modified membranes were confirmed through performance tests. The pristine PI nanofiltration membrane exposed to a 50 w/v% sulfuric acid for 4 h showed an increase in the normalized water flux to 205% and a decrease in the MgSO₄ normalized rejection to 44%, revealing damage to the membrane. The membrane modified by the Fenton reaction exhibited a decline in flux and improved rejection, which are typical performance changes after surface modification. However, the Fenton-modified membrane exposed to 50 w/v% sulfuric acid for 4 h showed a flux increase of 7% and a rejection increase of 4%, indicating improved acid resistance. Furthermore, the Fenton post-treatment enhanced the thermal stability and organic solvent resistance of the PI membrane. This study shows that the acid resistance of PI membranes can be successfully improved by a novel and facile Fenton reaction using green solvents.