Surface-modified polyimide on novel porous ceramic membranes for pervaporation desalination

Abstract

Although pervaporation (PV) desalination is a promising solution to global freshwater scarcity, membranes suffer from unstable separation performance. This study utilized resource recycling to prepare a porous ceramic membrane using solid waste fly ash as raw material, which was then combined with polyimide (PI) to produce a high-performance composite membrane (abbreviated to as PI/ceramic membrane). In this composite membrane, the ceramic membrane provides mechanical support and promotes rapid water passage, while the PI layer intercepts hydrated salt ions through size screening and electronic repulsion. Through their synergistic action, the composite membrane can preferentially adsorb and diffuse water molecules while retaining. Results indicate in addition to a retention efficiency of nearly 99.9%, the PI/ceramic membranes achieved a permeability of 10.88 L (m⁻² h⁻¹), which is superior to other existing polymer-modified membranes. Simultaneously, the membrane demonstrates selective ion rejection (e.g., SO₄²⁻ and Mg²⁺) while maintaining stable rejection performance at 90 °C. A 45-hour continuous operation test confirmed the composite membrane's stability, demonstrating consistent performance. This study provides a novel approach for the preparation of polymer-modified membranes for industrial wastewater desalination.