Discovery and Characterization of Silver Sulfide Nanoparticles in Final Sewage Sludge Products

Abstract

Nanosized silver sulfide (α-Ag(2)S) particles were identified in the final stage sewage sludge materials of a full-scale municipal wastewater treatment plant using analytical high-resolution transmission electron microscopy. The Ag(2)S nanocrystals are in the size range of 5-20 nm with ellipsoidal shape, and they form very small, loosely packed aggregates. Some of the Ag(2)S nanoparticles (NPs) have excess S on the surface of the sulfide minerals under S-rich environments, resulting in a ratio of Ag to S close to 1. Considering the current extensive production of Ag NPs and their widespread use in consumer products, it is likely that they are entering wastewater streams and the treatment facilities that process this water. This study suggests that in a reduced, S-rich environment, such as the sedimentation processes during wastewater treatment, nanosized silver sulfides are being formed. This field-scale study provides for the first time nanoparticle-level information of the Ag(2)S present in sewage sludge products, and further suggests the role of wastewater treatment processes on transformation of Ag nanoparticles and ionic Ag potentially released from them.

Metal‐based nanoparticles in soil: Fate, behavior, and effects on soil invertebrates

“…Nanoparticles are unlikely to enter the soil in their original form, however, because of the organically rich and reactive environments of WWTPs [30]. Silver sulfide NPs, found in sewage sludge, are suggested to have been formed from the reaction of Ag NPs with sulfide in a reductive environment [31].…”

“…Chem. 31,2012over nine months, with concomitant formation of a number of Zn precipitates [53]. However, the number of studies on NP dissolution in soil remains very small because of the technically challenging nature of such work.…”

Analysis of engineered nanomaterials in complex matrices (environment and biota): General considerations and conceptual case studies

“…Inorganic sulfide in wastewater effluent and receiving water has been shown to be present at concentrations that are 200 to 300 times in excess of the total Ag [87]. Silver sulfide has been identified recently in the form of nanoparticles (5-20 nm ellipsoids) in final stage sewage sludge materials in a full-sized municipal wastewater treatment plant [88]. Kim et al suggested, based on the results of Choi et al [86], that the source of the silver sulfide nanoparticles may have been engineered AgNPs.…”

Controlled Evaluation of Silver Nanoparticle Dissolution Using Atomic Force Microscopy

“…This conclusion is corroborated by a study that identified Ag 2 S nanoparticles in the effluent of fullscale WWTPs. 76 In marine environments, chloride may be the principal ligand influencing AgNP dissolution.…”