Electrospray-engineered magnetic-carbon/polypyrrole nanocomposite-embedded janus membrane in photothermal membrane...

Photothermal membrane distillation (PMD) has been widely explored for desalination, but its application for polluted groundwater remediation remains largely unexplored. In this study, a low-cost Janus Fe₃O₄@C/PPy-PVDF membrane was initially fabricated, featuring a hydrophilic top layer of Fe₃O₄@C/PPy nanoparticles for enhanced photothermal conversion and a hydrophobic PDMS-coated PVDF bottom layer for selective vapor transport. The Fe₃O₄@C/PPy composite synergistically combines Fe₃O₄ core semiconductor relaxation, carbon shell lattice relaxation, and PPy polaron/bipolaron transitions, enabling efficient light-to-heat conversion and rapid surface evaporation. Janus architecture facilitates continuous water replenishment, suppresses temperature and concentration polarization, and shortens vapor transport pathways. The optimized membrane (M23) achieved a maximum flux of 0.67 kg m^-2 h^-1 and photothermal evaporation efficiency of 41.92% under 1 kW m^-2 irradiation using polluted groundwater. For desalination performance, it achieved a 1.02 kg m^-2 h^-1 flux and 64% photothermal evaporation efficiency. The integrated MF-ADS-PMD process acquired the highest flux of 0.90 kg m^-2 h^-1, photothermal evaporation efficiency of 56.78%, and >99.7% chromium rejection from polluted groundwater. This study demonstrates that janus Fe₃O₄@C/PPy-PVDF membrane provides a sustainable and efficient PMD process for heavy metal-contaminated groundwater remediation, expanding the application of PMD beyond conventional desalination.