Evaluation of the Disinfectant Performance of Silver Nanoparticles in Different Water Chemistry Conditions

Abstract

This study aimed to determine the effect of different water chemistry conditions on the bactericidal properties of silver nanoparticles (AgNPs). Reduced disinfection performance of AgNPs was obtained in divalent cationic solutions in comparison with monovalent solutions with the same concentration. Average particle size of AgNPs increased with increasing electrolyte concentration as divalent cations (Ca2+ and Mg2+) produced larger AgNPs aggregates than those formed with monovalent solutions. ξ-potential measurements showed that AgNPs in divalent cationic solutions had low absolute ξ-potential values (-9.8 to -23.2 mV), whereas the values obtained in monovalent solutions were considerably more. The measurements of the concentration of ionic silver released indicated that the fraction of dissolved Ag+ (5.9–18.8 μg/L) was around 0.1% of the total mass of Ag0 added. The contribution of Ag+ to the overall disinfection performance was negligible at the conditions tested. In this study, different physicochemical properties of silver nanoparticles and the survival rate of Escherichia coli (E. coli) in different AgNPs solutions were analyzed. The data collected lead to a correlation between survival rate of E. coli and average size of AgNPs. The results show a strong correlation between these two parameters that can be fitted to a saturation type curve, reaching a survival plateau around 20% survival at an average particle size of 200 nm for all the water chemistry conditions tested.