Electrically-enhanced filtration of nanoplastics and natural organic matter via conductive CNT-based membrane: Synchronous removal and fouling mitigation

The co-existence of nanoplastics (NPs) and natural organic matter (NOM) in aquatic environments forms complex composite pollutants that severely accelerate membrane fouling and impair separation performance. In this study, an electrically conductive carbon nanotube/PEDOT/PVDF (CPP) composite membrane was fabricated via vacuum filtration and interfacial crosslinking to achieve simultaneous pollutant removal and fouling mitigation. The conductive network significantly enhanced membrane surface polarity under external negative potential. Under an external cathodic voltage of −2.0 V, the CPP membranes demonstrated notable synchronous separation performance during filtration of polystyrene (PS, 20 – 100 nm) and humic acid (HA) mixtures. Compared to open-circuit conditions, the applied negative potential boosted PS removal efficiency and achieved a stable HA removal rate. Meanwhile, the CPP membrane under external potential significantly suppressed flux decline, maintaining a high final normalized flux of 0.65 – 0.85. Fouling modeling analysis revealed that cake layer formation remained the dominant fouling mechanism and the external potential effectively inhibited foulant accumulation and promoted a looser deposition layer. This performance enhancement is governed by a multi-faceted electrically driven mechanism comprising enhanced electrostatic repulsion, electrophoretic migration of charged species, and induced electroosmotic flow within the membrane pores. Overall, this electrically enhanced filtration strategy offers an effective approach for treating natural surface water impacted by NPs composite fouling.