Photosynthesis of Au/TiO2 nanoparticles for photocatalytic gold recovery from industrial gold-cyanide plating wastewater

Abstract

A series of Aux/TiO2 nanoparticles (NPs) with different gold loadings (x = 0.1–1.0 wt%) was synthesized by the photodeposition and then employed as photocatalysts to recover precious component from the industrial gold-cyanide plating wastewater. Effects of Au loading, catalyst dosage and types of hole scavenger on the photocatalytic gold recovery were investigated under ultraviolet–visible (UV–Vis) light irradiation at room temperature. It was found that different Au loadings tuned the light absorption capacity of the synthesized photocatalysts and enhanced the photocatalytic activity in comparison with the bare TiO2 NPs. The addition of CH3OH, C2H5OH, C3H8O, and Na2S2O3 as a hole scavenger significantly promoted the photocatalytic activity of the gold recovery, while the H2O2 did not. Among different hole scavengers employed in this work, the CH3OH exhibited the highest capability to promote the photocatalytic gold recovery. In summary, the Au0.5/TiO2 NPs exhibited the best photocatalytic activity to completely recover gold ions within 30 min at the catalyst dosage of 0.5 g/L, light intensity of 3.20 mW/cm2 in the presence of 20 vol% CH3OH as hole scavenger. The photocatalytic activity slightly decreased after the 5th cycle of recovery process, indicating its high reusability.

Highly efficient ZnO/WO3 nanocomposites towards photocatalytic gold recovery from industrial cyanide-based gold plating wastewater

“… Photocatalysts Synthesis method Matrix/wastewater Operating conditions Gold recovery Ref Initial conc. of gold ions (mg/L) pH Light source (Intensity) Catalyst loading (g/L) Hole scavenger ZnO Solution combustion 60 n.d.* UV light 3 10 vol% CH 3 OH 100% (0.5 h) 21 rGO/TiO 2 (1 wt% rGO) Photoreduction 300 n.d LuzChem photoreactor (6 lamps, 365 nm) n.d 500 mL i-C 3 H 8 O ~ 30% (3 h) 23 Au/TiO 2 (0.5 wt% Au) Photodeposition 15 8.4–9.2 High pressure Hg lamp (3.20 mW/cm 2 ) 1 20 vol% CH 3 OH 100% (0.5 h) 24 TiO 2 /WO 3 (60 wt%) Hydrothermal 10–15 8.4–9.2 High pressure Hg lamp (3.20 mW/cm 2 ) 2 10 mM Na 2 S 2 O 3 and 20 vol% C 2 H 5 OH 98.2% (5 h) 80 ZnO/WO 3 (5 wt% ZnO) Hydrothermal 8–10 1...…”

“…Nevertheless, the reduction reaction of [Au(CN) 2 ] − is still sluggish due to its high negative reduction potential (− 0.57 V/NHE 19 ), thus limiting the use of variety photocatalysts. That is, only the photocatalysts that have a more positive VB position than the oxidation potential of OH − and also have a more negative CB position than the reduction potential of [Au(CN) 2 ] − can complete the photocatalytic gold recovery from the metal-cyanocomplexes contained solutions such as ZnO 20 , 21 , ZnS 22 , TiO 2 and TiO 2 -based materials 23 , 24 . Among all explored photocatalysts, it is noteworthy that TiO 2 or TiO 2 -based materials exhibited the best photocatalytic activity, probably due to its good surface property and high thermal-chemical resistance 25 , 26 .…”

Photocatalytic Gold Recovery from Industrial Gold Plating Effluent by ZnO Nanoparticles: Optimum Condition and Possible Applications

“…However, the utilization of gold-cyanide complexes faces a challenge due to their low reduction potential (−0.57 to −0.60 V/NHE , ), limiting their capability with photocatalysts possessing extremely low negative VB values. Among the well-established photocatalysts, titanium dioxide (TiO 2 ) or TiO 2 -based nanoparticles (NPs) have gained prominence as frequently utilized photocatalysts for gold recovery as well as metal removal/recovery due to their favorable textural property, robust photochemical and thermal stability, and environmental friendliness. ,,,,− …”