Silver ions in wastewater streams are a major pollutant and a threat to human health. Given the increasing demand and relative scarcity of silver, these streams could be a lucrative source to extract metallic silver. Wastewater is a complex mixture of many different metal salts, and developing recyclable sorbents with high specificity towards silver ions remains a major challenge. Here we report that molybdenum oxide (MoO_x) adsorbent with mixed-valence (Mo(V) and Mo(VI)) demonstrates high selectivity (distribution coefficient of 6437.40 mL g⁻¹) for Ag⁺ and an uptake capacity of 2605.91 mg g⁻¹. Our experimental results and density functional theory calculations illustrate the mechanism behind Ag⁺ adsorption and reduction. Our results show that Mo(V) species reduce Ag⁺ to metallic Ag, which decreases the energy barrier for subsequent Ag⁺ reductions, accounting for the high uptake of Ag⁺ from wastewater. Due to its high selectivity, MoO_x favorably adsorbs Ag⁺ even in the presence of interfering ions. High selective recovery of Ag⁺ from wastewater (recovery efficiency = 97.9%) further supports the practical applications of the sorbent. Finally, MoO_x can be recycled following silver recovery while maintaining a recovery efficiency of 97.1% after five cycles. The method is expected to provide a viable strategy to recover silver from wastewater.

Pesticides are chemicals used in agriculture, industry, and households to control pests and enhance crop yields but have emerged as pollutants in soil and water due to their presence in domestic and agricultural wastewater effluents. The World Health Organization (WHO) has identified the development of pesticide resistance as a significant threat to global public health. Consequently, removing pesticides in aqueous environments has gained considerable attention. Numerous methodologies, including biological, physical, and chemical methods, have been employed for their treatment. Among these methods, advanced oxidation processes (AOPs) have garnered particular interest due to their fast reaction rates and strong oxidizing abilities. This review focuses on various AOPs such as Fenton and Fenton-like oxidation, ozonation, the UV/H₂O₂ process, electrochemical oxidation, photocatalytic oxidation, and the UV/O₃ process. The review analyzes and summarizes the current applications of these AOPs for treating pesticides in aqueous environments. It also compares various AOPs treatment methods and discusses the challenges, drawbacks, advantages, and strategies for addressing these issues, and provides insights into the future prospects. Finally, it propose potential strategies and areas of improvement for future research to enhance the efficiency and sustainability of AOPs in practical application.