Charge-size synergistic screening of GO/PSBMA nanofiltration membranes: for dye desalination and anti-fouling mechanism studies

A novel graphene oxide (GO)-based nanofiltration membrane was engineered to tackle the selective separation challenge of dyes and inorganic salts in salt-laden textile wastewater. Highly hydrophilic sulfobetaine methacrylate (SBMA) was covalently graft-polymerized onto GO surfaces to fabricate amphoteric polymer nanosheets (PSBMA@GO). Subsequent physical intercalation with pristine GO nanosheets yielded the GPM1:2 composite membrane. This strategy effectively enlarged the interlayer channels, endowing the membrane with a significantly enhanced permeability of 31.53 L·m⁻¹ h⁻¹ bar⁻¹, markedly surpassing that of the pristine GO membrane (12.26 L·m⁻¹ h⁻¹ bar⁻¹). The zwitterionic modification preserved the inherent negative charge of GO. The synergistic interplay between membrane surface charge regulation and precise pore size control achieved exceptional dye/salt separation selectivity. Dyes were selectively rejected via the Donnan exclusion effect, with rejection rates for Methylene Blue (MnB) and Congo Red (CR) exceeding 99.47 % and 98.7 %, respectively. Concurrently, efficient permeation of mono/divalent salt ions was facilitated (NaCl: 96.83 %; Na₂SO₄: 95.8 %). Furthermore, the zwitterionic polymer conferred exceptional anti-fouling properties, evidenced by a high flux recovery rate (FRR) of 89.15 % following bovine serum albumin (BSA) fouling. The FRR remained above 80 % even after a rigorous 10-h dynamic cycling test. This study establishes a novel paradigm for designing high-efficiency dye wastewater treatment membranes through the synergistic optimization of interfacial functionalization and structural modulation.