Reduction of Gold from Plating Wastewater Using TiO_2 Photocatalyst

摘要

TiO_2 photocatalyst has attracted much attention in recovering valuable metal ions from industrial wastewater because TiO_2 shows chemical stability and good wear resistant, and a photocatalytic reaction occurs by illumination of the sun or fluorescent light. In this study, Au removal and recovery in a gilding wastewater using TiO_2 photocatalyst was evaluated. Commercially obtained TiO_2 powder and TiO_2 film prepared by spray and screen print method were used for Au adsorption. The cyanide existed in a plating wastewater was firstly removed with peroxide or persulfate because a driving force for Au ion reduction during photocatalytic process could decrease by the existed cyanide. Compared with persulfate, peroxide shows relatively slow removal rate of cyanide but no precipitation occurs. With respect to photocatalytic reaction of TiO_2 powder and film for Au removal and recovery, it was found that the addition of 10 vol% of methanol as a hole scavenger increases the rates of Au ion reduction and Au adsorption on the TiO_2 powder and film, subsequently the reaction of Au photoadsorption was completed within 60 min. Au lumps on the TiO_2 particles obtained by photocatalytic reduction of TiO_2 was confirmed by XRD analysis and TEM observation.