A super-hydrophilic separation layer on polyethersulfone conductive composite membranes for efficient dyeing wastewater treatment

Effective dye removal from wastewater plays a vital role in safeguarding the environment and enabling the reuse of water resources. Membrane separation is regarded as an ideal choice for treating dyeing wastewater. However, complex dyeing wastewater poses significant challenges for membrane technology, where the need for selective separation and membrane fouling impede its broader application. Herein, a stable super-hydrophilic separation layer was constructed on polyethersulfone (PES) conductive composite membranes via the co-assembly of polyvinyl amine (PVAM) and tannic acid (TA). This design leveraged the synergistic effects between superhydrophilicity and electrical responsiveness to achieve excellent separation and antifouling performances against various dyes. Moreover, the compactness of separation layers was precisely manipulated by adjusting the TA concentration to further optimize the membrane performance through maximizing the size-sieving effect. Consequently, in the electro-assisted filtration, the optimal membrane delivered high rejection and permeation flux for negatively charged Congo red (≥95.4 ± 1.0 %, ≥266.1 ± 16.6 L/m 2 ·h·bar) as the cathode and for positively charged methyl green (≥95.1 ± 1.1 %, ≥401.8 ± 22.5 L/m 2 ·h·bar) as the anode. Simultaneously, the combination of enhanced electrostatic repulsion and the scouring from electrolytically generated micro/nano bubbles enabled the superior flux recovery ratios for Congo red (97.6 ± 1.2 %) at -3V and methyl green (98.2 ± 1.3 %) at + 3 V, indicating excellent antifouling properties. Furthermore, the membrane also exhibited highly stable permeate fluxes and rejections over 36 h of continuous filtration and five cycles, demonstrating its promise for practical application in treating dyeing wastewater. This study proposes a novel fabrication strategy for next-generation intelligent membranes, thereby promoting the precise treatment of complex wastewater.