Highly-efficient recovery of silver from industrial cyanide-based plating effluent on TiO2/activated carbon composites

The release of silver-containing wastewater is an economic loss. In this works, the silver ions in the cyanide-based plating effluent of jewelry effluent was systematic recovered by the photocatalytic process using commercial semiconductors (TiO₂, ZnO, Bi₂O₃ and WO₃) and activated carbon (AC) enhanced semiconductors as the photocatalysts. The preliminary results demonstrated that the highest photocatalytic silver recovery was achieved via the use of TiO₂ nanoparticles (NPs), ascribing to its better textural property that provided abundant active sites to undergo the reaction. The intrinsic property and activity of TiO₂ were significantly improved in the presence of proper content of AC. Approximately 94% of silver was recovered within 45 min through the TiO₂/AC with 14.9 wt% AC (TiO₂/AC1) under the UV–vis irradiation due to the act of AC as the conductive pathway for electron migration from CB of TiO₂ along its surface, thus prolonging the lifetime of electron-hole pairs. Although a marked decrease in photocatalytic activity of the best composite was detected after the 4th use (∼50%), it exhibited an outstanding antibacterial ability compared with TiO₂ and fresh one in dark environment. The work offers the avenue to design the photocatalyst for recovering the precious metals from industrial effluent and broaden the application of such recovered metal decorated photocatalyst for practical use.