Surface-Engineered Polythiosemicarbazide Membranes via Chelation-Controlled Silver Nanoparticle Growth for Antibacterial and Underwater Oleophobic Performance

Biofouling continues to limit the performance of ultrafiltration membranes for oil–water separation, creating demand for materials that combine high flux, strong selectivity, and built-in antimicrobial activity. Here, we report a chelating polythiosemicarbazide (PTSC) ultrafiltration membrane that supports in situ growth of silver nanoparticles through intrinsic Ag+ coordination and controlled chemical reduction. PTSC membranes were prepared by nonsolvent-induced phase separation using 12 wt% PTSC, loaded with Ag+ and reduced with NaBH4. PTSC showed high Ag+ uptake, reaching about 365 mg g–1 at 250 ppm with less than 3% silver release after prolonged immersion. The modified membrane remained highly hydrophilic and strongly underwater oleophobic, with oil contact angles above 100° for several oils. It showed a molecular weight cutoff near 270 kDa and delivered 97–99% oil rejection, a permeance of about 110–230 L m–2 h–1 bar–1, and antibacterial activity against Bacillus thuringiensis. These results highlight a strategy for multifunctional membranes with minimized silver leaching and fouling resistance.