Self-Heating Graphene Oxide Composite Membranes for Desalination via Photothermal Membrane Distillation

In this work, we develop a simple and scalable fabrication method for the preparation of stable and efficient self-heating membranes that combine the excellent photothermal conversion efficiency of graphene oxide (GO) and the hydrophilic properties of polyvinyl alcohol (PVA) for photothermal membrane distillation (PMD) applications. Our results demonstrated that Janus composite membranes comprising a thin layer of GO-loaded PVA hydrogel on a porous polyvinylidene fluoride (PVDF) support can offer a dual advantage: the hydrophilic GO-loaded hydrogel provides localized heating under light irradiation and resistance to scaling, while the hydrophobic substrate offers excellent wetting resistance and allows water evaporation under thermal gradients. As a result, a 190% flux increase with 99.99% salt rejection was achieved for a 35 g L−1 NaCl feed solution under 1 sun irradiation with 2 wt.% GO-filled composites, achieving a photothermal conversion efficiency of 70% and a specific thermal energy consumption approximately 25% lower than the latent heat of evaporation of water at the operating temperature. Detailed computational fluid dynamics (CFD) simulations allowed us to evaluate the thermal profiles across the membrane module and calculate the temperature polarization coefficient (TPC) that ranged from 0.8 to 1.2 for the light ON-state. Our results also demonstrated the fundamental dependence of process performance on solution velocity and GO loading, which establishes a key tradeoff for the efficient applicability of this technology to water desalination.