Fe3O4/PVDF-HFP photothermal membrane with in-situ heating for sustainable, stable and efficient pilot-scale solar-driven membrane distillation

Solar-driven membrane distillation (SDMD) is a newly developed desalination technique with promising potential to address the global shortage of freshwater resources. However, this technique still suffers from tedious and high cost synthesis process for the photothermal composite membrane, and low conversion efficiencies for photothermal energy. Herein, we prepared a Fe3O4/polyvinylidene fluoride-co-hexafluoropropylene (Fe3O4/PVDF-HFP) absorber by vacuum-assisted filtration, which exhibited strong interfacial adhesion due to coordination between Fe3O4 nanoparticles and PVDF-HFP nanofibers, thus showing excellent performance for SDMD. Benefiting from the excellent absorption of solar energy by Fe3O4 nanoparticles and the high porosity of Fe3O4/PVDF-HFP membrane, the transmembrane temperature was increased and the transmembrane resistance of vapor was reduced significantly. The photothermal membrane showed a permeate flux of 0.97 kg m−2 h−1 with a salt rejection rate of 99.99% under 1 kW m−2 solar irradiation, and the photothermal conversion efficiency is among the highest (53%) reported so far. Furthermore, such a composite membrane worked stably in a pilot-scale system and demonstrated a 21.99 kg m−2 h−1 which is 11% higher than the solar-free system, thus manifesting its great prospect for practical applications.