Photo-assisted rapid recovery of silver from cyanide-based plating effluent of jewelry industry using Bi2WO6 nanoparticles

Abstract

Discharging effluent containing silver cyanide complexes causes economic loss and is harmful to humans and other living organisms. In this work, a rapid recovery of silver from cyanide-based plating effluent was conducted via Bi<inf>2</inf>WO<inf>6</inf> nanoparticles (NPs) through the photocatalytic process. The effect of calcination temperature on the synthesis of Bi<inf>2</inf>WO<inf>6</inf> and its impact on the properties and photocatalytic activity were first explored and then the optimum operating condition was investigated. It was found that Bi<inf>2</inf>WO<inf>6</inf> NPs synthesized at 350 °C (BWC35) exhibited the highest photocatalytic activity for silver recovery, owing to its high active surface area. The Na<inf>2</inf>S<inf>2</inf>O<inf>3</inf> concentration, C<inf>2</inf>H<inf>5</inf>OH concentration and photocatalyst loading played an essential role on the photocatalytic silver recovery. Under optimum conditions, approximately 99 % of silver ions was decorated on the BWC35 NPs within 30 min, resulting the formation of Ag/Ag<inf>2</inf>S@BWC35 NPs, which exhibited outstanding photocatalytic properties for dye degradation and H<inf>2</inf> production. The reusability of the BWC35 NPs for silver recovery was stable over five reuse cycles. Results obtained from this work may broaden the understanding of the rapid recovery of precious metals from industrial plating effluent through the photocatalytic process and facilitate the application of the resulting metal-decorated photocatalyst in other applications.