Polyethersulfone (PES) ultrafiltration (UF) membranes loaded with silver nitrate for bacteria removal

PES UF membranes containing silver were prepared to impart antibacterial properties for waste water treatment. Asymmetric membranes for antibacterial application were prepared from polyethersulfone (PES) and silver nitrate (AgNO3) (PES/AgNO3=15/2 by weight) solution in N-Methyl-2-pyrrolidone (NMP) via simple wet phase inversion technique. These membranes were characterized by polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) of different molecular weights (1000 ppm in water) at room temperature and on operating pressure of 5 bars. It was observed that the water flux of PES-AgNO3 membrane is slightly lower than virgin PES but still increased linearly with the increment of pressure applied. The morphology of the resulting membranes was examined using Field-Emission Scanning Electron Microscope (FESEM) coupled with Energy Dispersive Spectroscopy (EDS). Elemental analysis using EDS proved that silver is successfully loaded on the membrane surfaces. Due to the success of loading silver on membrane surfaces, antibacterial activities were evaluated via agar diffusion method against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) culture. By incorporating 2 wt% of silver nitrate, PES-AgNO3 showed significant inhibition ring on both E.coli and S.aureus. Filtration of E.coli solution (OD 0.31) showed satisfactory rejection data with similar to 100% inhibition growth after 24 hours incubation at 37 degrees C. Resultant membranes also exhibit better tensile strength (compared to virgin PES) up to 71% may be due to the suggested interactions. The residual silver during fabrication was measured using ICP-MS and result showed that the residual silver content of PES-AgNO3 membrane was only similar to 1% of the original silver added in the polymer solution. These studies have shown that PES-AgNO3 UF membranes are potential in improving the filtration in water treatment.