Sustainable electrospray polymerization fabrication of thin-film composite polyamide nanofiltration membranes for heavy metal removal

Thin-film composite polyamide (TFC-PA) nanofiltration membrane is promising in heavy metal removal due to its excellent performance and high economic benefits. However, the common interfacial polymerization (IP) fabrication method requires abundant toxic and harmful solvents, causing harm to the environment and humans. Therefore, novel green, low-carbon and sustainable fabrication methods are urgently needed. Here, we reported a sustainable electrospray polymerization (SEP) technique for TFC-PA membrane preparation via electrospray featuring no toxic solvent, near-complete monomer conversion , and zero waste liquid discharge. In this process, 2-methyl-tetrahydrofuran and ethanol were used as green solvents, and its greenness was assessed by green metrics and toxicity bioassays. Physical features and physicochemical properties of SEP membranes were characterized by SEM, TEM, AFM and XPS. Membranes with different surface charges and pore sizes could be tailored by varying the monomer concentration . The optimal membrane exhibited excellent removal efficiency of toxic heavy metal ions , in which the rejection rates of Cu 2+ and Ni 2+ were higher than 97.0 %. In addition, the permeability and salt rejection of SEP membranes were better than those of IP membranes. Our sustainable electrospray polymerization method provides a versatile green platform for fabricating TFC membranes and may facilitate the development of sustainable nanofiltration membranes.