The fate of Ag nanoparticles (NPs) released from domestic and industrial discharges to municipal wastewater treatment plants is dependant in part on the dissolution of the NPs in municipal wastewaters with complex chemistry. In this study we developed a method for measuring the nanoparticulate and dissolved concentrations of silver, as well as the diameters of Ag NPs, in wastewater effluent using Single-Particle Mode Inductively Coupled Plasma Mass Spectrometry (SP ICP-MS). We characterized the dissolution and aggregation of Ag NPs in municipal wastewater over several hours by SP ICP-MS. Ag NPs, 80 nm in diameter, with citrate and PVP coatings, at concentrations of 1 ppm and 0.5 ppb were added to filtered effluent wastewater of similar aqueous composition to an activated sludge reactor, deionized water or solutions of bovine serum albumin (BSA), a model wastewater organic molecule. The dissolution and aggregation of NPs in deionized water was negligible as determined from lack of change in dissolved Ag ions or in the NP diameter over 6 h. However in the effluent wastewater and BSA solution aggregation and dissolution of NPs was observed within 6 h. The particle size distribution from both nanoparticle tracking analysis (NTA) and SP ICP-MS confirmed the formation of large particles of up to 250 nm in diameter within the first 6 hours of exposure to the filtered wastewater effluent. The concentration of dissolved Ag ions from PVP-Ag NPs reached 10% of the total Ag mass within the first 4 h of exposure to 20 and 100 ppm BSA whereas in filtered effluent wastewater the same amount of dissolved Ag ions released within 48 h of exposure. Results on the dissolution kinetics of partially sulfidated Ag NPs in the presence of wastewater and organic matter (i.e. DOC) will also be presented.

Dissolution kinetics of silver nanoparticles in municipal wastewaters by single particle mode ICP-MS

248th National Meeting (2014)

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