Microbial disinfection of water with endotoxin degradation by photocatalysis using Ag@TiO 2 core shell nanoparticles

Abstract

The studies on photocatalytic disinfection of water contaminated with Escherichia coli using Ag core and TiO₂ shell (Ag@TiO₂) nanoparticles under UV irradiation showed that these nanoparticles are very efficient in water disinfection both in their free and immobilised form. Complete disinfection of 40 × 10⁸ CFU/mL could be achieved in 60 min with 0.4 g/L catalyst loading and in 35 min with 1 g/L catalyst loading. Ag@TiO₂ nanoparticles were found to be superior to TiO₂ nanoparticles in photocatalytic disinfection of water. Kinetics of disinfection followed Chick's law, and the pseudo-first-order rate constant was 0.0168 min⁻¹ for a catalyst loading of 0.1 g/L. Disinfection of water and degradation of endotoxins (harmful disinfection residual) occurred simultaneously during photocatalysis thereby making the treated water safe for use. Endotoxin degradation showed a shifting order of kinetics. The rate of photocatalysis with nanoparticles immobilised in cellulose acetate film was marginally lower as compared to that of free nanoparticles. Negligible Ag ion leakage and re-growth of cells post-photo-catalytic treatment of water confirmed that complete disintegration of E. coli occurred during photocatalysis making the treated water safe for use. Therefore, Ag@TiO₂ nanoparticles have a potential for large-scale application in drinking water treatment plants and household purification units.

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