Photocatalytic water disinfection under solar irradiation by Ag@TiO2 core-shell structured nanoparticles

Abstract

The Ag core-TiO<inf>2</inf> shell structured (Ag@TiO<inf>2</inf>) nanoparticles were found to be efficient in the disinfection of water under solar light irradiation both in free and immobilized form. Complete disinfection of 40 ? 108 CFU/mL Escherchia coli cells was achieved in 15 min by solar photocatalysis with 0.4 g/L Ag@TiO<inf>2</inf> catalyst loading. Ag@TiO<inf>2</inf> nanoparticles were found to be superior to TiO<inf>2</inf> nanoparticles in solar disinfection. Photocatalysis rate was found to increase with increase in catalyst loading and with decrease in cell concentration. Ag@TiO<inf>2</inf> nanoparticles showed their efficacy in the degradation of endotoxin, a harmful disinfection byproduct. Kinetics of solar disinfection with Ag@TiO<inf>2</inf> nanoparticles followed Chick's law. The kinetics of endotoxin degradation followed zero order kinetics at high concentrations of endotoxin. However at lower concentrations, rate followed a nth order model with n = 6.99. A lower rate of photocatalytic disinfection with Ag@TiO<inf>2</inf> nanoparticles immobilized on cellulose acetate as compared to that in their free form was observed, owing to diffusional and light penetration limitations. The re-growth of cells after photocatalytic disinfection was below the detectable limits, thus proving the potential of the process to produce safe drinking water. Ag@TiO<inf>2</inf> nanoparticles can find potential application in solar water disinfection and the process which harnesses the solar energy may prove to be energy efficient and economical, thus can be easily adopted for large scale applications and portable drinking water treatment units for domestic applications. © 2017 Elsevier Ltd