Solar light-Ag@ZnO Nanocomposite System Disinfects Water Borne Pathogens

The present study investigates the in-situ disinfection of water borne pathogens like Escherichia coli in aqueous matrix using Ag@ZnO photocatalyst irradiated with sunlight. Survival of the pathogens was assessed by counting on agar plates and the mechanistic understanding of bacterial inactivation was studied through lipid peroxidation and potassium ion leakage analyses. Interestingly, production of Malondialdehyde during the photocatalytic process along with the presence of potassium ion in the reaction environment may suggest the possible disruption of bacterial cell architecture, which is expected to be the preliminary mechanism in disinfection activity. As an integral part of this investigation photocatalytic disinfection process development and optimization of reaction parameters has also been discussed with the help of mathematical models. Disinfection of pathogens was correlated with standard Chick Watson disinfection model. Disinfection efficiency in laboratory as well as real water samples was compared with that of pure-ZnO and TiO₂(Degussa P25). Nanocomposite system has shown optimum disinfection (≈99%) at 40~60 min of sun-light exposure with a catalyst loading of 0.6 mg/L of the reaction solution. The reduction of aquatic bacterial densities by photocatalytically active Ag@ZnO core-shell nanocomposite in presence of natural sun-light may have potential ex situ application in water decontamination at ambient conditions.