Surface-decorated polyethylene glycol-graphene oxide nanohybrids for fouling mitigation in aminated polysulfone membranes treating oily wastewater

Abstract

Membrane fouling remains a critical challenge in oily wastewater treatment, limiting the efficiency of conventional polymeric membranes. Graphene oxide (GO) is a promising hydrophilic modifier, but its tendency to restack restricts interlayer spacing and limits antifouling performance. In this work, we present polyethylene glycol (PEG)-functionalized GO nanosheets, with adjustable molecular weights, to effectively expand GO interlayer spacing and enhance the hydrophilicity and antifouling capabilities of aminated chloromethylated polysulfone (AM-CMPSF) membranes. PSF was first chloromethylated and fabricated via non-solvent induced phase separation method, followed by amination using ethylenediamine to form AM-CMPSF membranes. GO nanosheets were synthesized and functionalized with PEG of varying molecular weights, then stacked onto the membrane surface. XRD analysis confirmed that increasing PEG molecular weight broadened interlayer d-spacing between GO nanosheets. The resulting GO-PEG/AM-CMPSF membranes exhibited significantly improved surface hydrophilicity, with rapid water absorption preventing contact angle measurement, and increased water uptake (from 30.6% for the pristine membrane (M0) to 84.6% for GO-PEG20000 (M6)), and pure water flux (from 5.9 to 16.9 L·m−2·h−1). Filtration tests using a 1000 mg·L−1 oil-in-water emulsion revealed enhanced permeate flux and fouling resistance. All membranes maintained high oil rejection (85.6% - 88.1%). Permeate flux decline decreased from 41.2% for M0 to 27.2% for M6, irreversible fouling ratio from 28.6% to 23.0%, and the flux recovery ratio increased from 71.2% to 87.0%. The results demonstrate that PEG-modified GO effectively enhanced membrane hydrophilicity, antifouling behavior, and filtration performance, offering a promising strategy for advanced oily wastewater treatment.