Synthesis, multi-site transformation fate and biological toxicity of silver nanoparticles in aquatic environment: A review

Silver nanoparticles (AgNPs) are widely used due to its unique physicochemical properties and efficient antimicrobial performance, therefore a large number of AgNPs have entered the aquatic environment and attracted extensive academic attention. This review introduces several commonly used methods for the preparation of AgNPs, including physical synthesis (ball milling, evaporative condensation, and laser ablation), chemical synthesis (chemical reduction, microemulsion, and microwave-assisted synthesis), and green synthesis methods for the preparation of AgNPs using microbial or plant extracts. This is followed by an overview of the applications of materials containing AgNPs and the pathways of AgNPs into the aquatic environment. Then, a comprehensive review of the research progress on the migration and transformation of AgNPs in natural water, sediment, wastewater, and wastewater treatment plants is presented. The transformation behavior of AgNPs in natural freshwater, sewage, and sediments includes aggregation and sedimentation, oxidative dissolution, sulfation, and chlorination, where the AgNPs in sewage and sediments end up in the form of sulfides. AgNPs in wastewater plants affect microbial activity and the removal of organic matter, nitrogen, and phosphorus during biological treatment. Finally, the toxic effects of AgNPs on microorganisms, animals, and plants after discharge into the aquatic environment are summarized. This work presents a full-process, multi-faceted analysis and review of the migration and transformation of AgNPs in aquatic environments, providing a theoretical reference for further research related to AgNPs. & COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).