Electrospray-engineered Magnetic-Carbon/Polypyrrole Nanocomposite-embedded Janus Membrane in Photothermal Membrane Distillation for Polluted Groundwater.

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.