Surface modification of commercial anion exchange membrane for the inactivation of Escherichia coli

Abstract

Modifying membranes with antimicrobial nanoparticles enhances antifouling properties and enables rapid disinfection during water treatment. Here, silver (Ag) and copper (Cu) particles were formed on a commercial anionic exchange membranes using a two-step ion-mediated surface-reduction process consisting of a 24-h sodium borohydride treatment followed by a 24-h reaction with Ag and Cu precursor solutions (0.01–0.1 M). Scanning electron microscopy with energy-dispersive spectrometry confirmed uniform Ag and Cu particle distribution on the membrane surface. Increasing precursor concentration enlarged the Ag particle diameters from 167.7 ± 2.2 nm to 652.2 ± 23.4 nm and Cu from 117.8 ± 3.4 nm to 606.5 ± 16.6 nm, with metal content of 0.05 ± 0.001–0.17 ± 0.01 mg·cm2 (Ag) and 1.05 ± 0.01–2.13 ± 0.03 mg·cm2 (Cu). Metal leaching after 14 days was low (Ag: 3.11 ± 0.24–6.62 ± 0.12 ppb; Cu: 2.75 ± 0.1–5.32 ± 0.1 ppb), within World Health Organization drinking water limits. The modified membranes achieved up to 8-log inactivation of Escherichia coli within 1–4 h. The most effective Ag and Cu membranes (lowest metal loading) exhibited specific inactivation rates of 13.68 ± 0.93 (mg·cm2)⁻1 for Ag and 1.69 ± 0.14 (mg·cm2)⁻1 for Cu in 2 h. Ag exhibited the highest antimicrobial efficiency per unit metal, while high-loading Cu disinfects fastest, together showing metal-modified anionic membranes provide stable, low-leaching antimicrobial performance suitable emergency treatment.