Development of heterostructure composite membranes with scalable polymer-based coating layers for enhanced membrane distillation

Membrane distillation (MD) holds promise for high-salinity wastewater treatment, but its industrial deployment is hindered by membrane wetting, fouling and temperature polarisation. Conventional MD membranes lack the chemical versatility and structural design needed to simultaneously overcome these limitations. To address these gaps, a scalable dual-layer membrane consisting of a poly (vinyl alcohol) (PVA)/graphene oxide (GO) hybrid layer on a microporous polytetrafluoroethylene (PTFE) support was developed, aiming to enhance wetting/fouling resistance and maintain stable separation performance. The PVA based layer was manipulated to exhibit tuneable physicochemical properties due to the interfacial compatibility between GO and PVA. The thermal conductivities of the dual-layer membranes were heterogeneous, featuring alleviated temperature polarisation. When applied in the direct contact MD process, the dual-layer membranes exhibited noticeably enhanced stability in comparison with the pristine PTFE membrane. Using an aqueous feed mixture containing 0.4 mM sodium dodecyl sulfate and 3.5 wt% NaCl, the composite membrane with 3 wt% GO loading achieved a 25 % increase in water vapor flux compared to pristine PTFE, while maintaining 99.9 % salt rejection at 50 °C (with a permeate temperature of 10 °C). Furthermore, the improved membrane stability was further validated by real landfill leachate treatment, where the 3 wt% GO composite membrane consistently yielded high-quality permeate throughout a 50-h long-term durability test. These results demonstrate a strategy for designing scalable MD membranes with improved stability and thermal efficiency, advancing their potential for industrial applications.