Novel CNT/MXene composite membranes with superior electrocatalytic efficiency and durability for sustainable wastewater treatment

Abstract

Self-assembled composite membranes are increasingly acknowledged for their potential in wastewater treatment due to their superior selectivity, high operational efficiency, and environmental sustainability. Nonetheless, challenges such as inadequate removal efficiencies for low molecular weight dyes and significant membrane fouling restrict their broader industrial application. To address these challenges, a structurally stable composite membrane of sodium lignosulfonate carbon nanotubes/alkalized MXene (SLS-CNT/alk-MXene) has been engineered. This membrane employs a polyethersulfone substrate pretreated with dopamine for uniform nanoparticle assembly through a layer-by-layer self-assembly technique. The manufacturing process includes hydrophilic modification of carbon nanotubes with lignosulfonate, followed by alkalization of MXene using sodium hydroxide. Performance evaluation of the M2 composite membrane, with a content ratio of SLS-CNT to alk-MXene of 4:2 by weight, revealed outstanding membrane properties. It achieved high selective permeability, with over 99 % retention efficiency for Methyl Blue and Congo Red, and a permeation flux of 51.6 L m-2h−1 bar−1. This membrane efficiently degraded various organic dyes within 1h, including Methyl Orange, Methylene Blue, Malachite Green, and Rhodamine B, and thanks to the integration of electrocatalysis with membrane separation, while maintaining a low membrane resistance of only 813 Ω. After environmentally sustainable testing, the membrane displayed excellent stability and 80 % recovery capacity, presenting a novel approach and design blueprint for enhancing clean water resources and environmental protection.