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Discharging the gold-contained wastewater is an economic loss. In this work, a set of ZnO/WO3 was facile synthesized by hydrothermal method in order to recover gold from the industrial cyanide-based gold plating wastewater by photocatalytic process. Effect of ZnO contents coupled with WO3 was first explored. Then, effects of operating condition including initial pH of wastewater, type of hole scavenger, concentration of the best hole scavenger and photocatalyst dose were explored. A series of experimental results demonstrated that the ZnO/WO3 nanocomposite with 5 wt% ZnO (Z5.0/WO3) depicted the highest photocatalytic activity for gold recovery due to the synergetic effect of oxygen vacancies, a well-constructed ZnO/WO3 heterostructure and an appropriate band position alignment with respect to the redox potentials of [Au(CN)2]− and hole scavengers. Via this ZnO/WO3 nanocomposite, approximately 99.5% of gold ions was recovered within 5 h using light intensity of 3.57 mW/cm2, catalyst dose of 2.0 g/L, ethanol concentration of 20 vol% and initial pH of wastewater of 11.2. In addition, high stability and reusability were observed with the best nanocomposite even at the 5th reuse. This work provides the guidance and pave the way for designing the ZnO/WO3 nanocomposite for precious metal recovery from a real industrial wastewater. [ABSTRACT FROM AUTHOR]

In this work, the green H 2 production and decolorization of industrial distillery effluent were carried out by the photocatalytic process via a gold-decorated TiO 2 photocatalyst synthesized by the photodeposition. Effects of dilution (0–150 folds), decorated gold content on TiO 2 (0.1–0.7 wt%), ethanol concentration (0–20 vol%) and photocatalyst loading (2–5 g/L) on the photocatalytic activity were explored. The preliminary results illustrated that neither H 2 production nor decolorization were achieved via the fresh distillery effluent. The maximum H 2 production of 210 μmol/g with 64.4 % decolorization was achieved with the 100-fold diluted-distillery effluent using the 0.3 wt% gold decorated on TiO 2 (Au 0.3 T) photocatalyst at loading of 3 g/L and ethanol concentration of 15 vol%. The characterization and experiment results pointed out that the improved photocatalytic activity of Au 0.3 T photocatalyst was based on the available area of decorated gold nanoparticles (NPs), the Au–TiO 2 interface area and interface perimeters. Via the distillery effluent, the water splitting was the dominate reaction for H 2 production, accounting of around 93% of overall produced H 2. Although a low recycling stability was observed from this work, attributing to the accumulation of organic contaminants founded in the distillery effluent on the surface of the photocatalyst, this finding may pave the way for the design of metal-decorated semiconductors for simultaneous green H 2 production and pollutant removal from actual industrial wastewater. • The H 2 production and decolorization of distillery effluent were conducted via Au/TiO 2. • About 210 μmol H 2 /g with 64.4 % decolorization was achieved via Au 0.3 T photocatalyst. • Area of decorated gold and interface area/perimeters affected the H 2 production. • 93% of overall produced H 2 from was distillery effluent coming from water splitting. [ABSTRACT FROM AUTHOR]

A series of nonmetal-doped titanium dioxide (Nm x /TiO 2 , where x is the weight fraction of nonmetal elements) photocatalysts was prepared via ultrasonic-assisted impregnation for simultaneous hydrogen (H 2 ) production and chemical oxygen demand (COD) removal from industrial wastewater. Three types of Nm elements, carbon (C), silicon (Si), and phosphorus (P), were explored. The P 1 /TiO 2 exhibited a higher photocatalytic activity for H 2 production and COD removal than the C 1 /TiO 2 and Si 1 /TiO 2 photocatalysts. Approximately 6.43 mmol/g photocatalyst of H 2 was produced, and around 26% COD removal was achieved at a P 1 /TiO 2 loading of 4.0 g/L, a light intensity of 5.93 mW/cm 2 , and a radiation time of 4 h. This is because the P 1 /TiO 2 photocatalyst exhibited lower point of zero charge values and a more appropriate band position compared with other Nm x /TiO 2 photocatalysts to produce H + , which can consequently form H 2 , and reactive oxygen species (HO · and O 2 · - ), which serve as oxidizing agents to degrade the organic pollutants. Increasing the content of the P element doped into the TiO 2 -based material up to 7.0% by weight enhanced the H 2 production and COD removal up to 8.34 mmol/g photocatalyst and 50.6%, respectively. This is attributed to the combined effect of the point of zero charge value and the S BET of the prepared photocatalysts. The photocatalytic activity of the P 7 /TiO 2 photocatalyst was still higher than the TiO 2 -based material after the fourth use., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)