New Insights into the Stability of Silver Sulfide Nanoparticles in Surface Water: Dissolution through Hypochlorite Oxidation.

Silver sulfide nanoparticles (AgSNPs) are considered to be stable in the environment due to the extreme low solubility of AgS (K: 6.3 × 10). Little is known about the stability of AgSNPs in surface water disinfected with aqueous chlorine, one of the globally most used disinfectants. Our results suggested that both uncoated and polyvinylpyrrolidone (PVP)-coated AgSNPs (100 μg/L) underwent dissolution in surface water disinfected with aqueous chlorine at a dose of 4 mg/L, showing the highest dissolved silver ion concentrations of 22.3 and 10.5 μg/L within 45 min, respectively. The natural organic matter (NOM) and dissolved oxygen (DO) posed effects on the AgSNPs dissolution by chlorine; NOM accelerated AgSNPs dissolution while DO reduced the rate and extent of AgSNPs dissolution. We further demonstrated that AgSNPs dissolution was primarily attributed to active oxidative substances including hydroxyl radical and HO originating from the hypochlorite oxidation. Additionally, water containing AgSNPs disinfected with hypochlorite showed stronger interference on the zebra fish (Danio rerio) embryo hatching than AgSNPs and hypochlorite on their own. This work documented that AgSNPs could undergo dissolution in surface water through hypochlorite oxidation, posing potential risks to aquatic organisms, and therefore showed new insights into the stability of AgSNPs in natural environment.