Cu(0)/TiO2 composite byproduct from photo-reduction of acidic Cu-containing wastewater and its reuse as a catalyst

Acidic low-concentration copper-containing wastewater is technically a type of refractory wastewater. In this study, a TiO2 photocatalyst was used to photo-deposit Cu(II) from a Cu-containing dilution to produce a usable Cu(0)/TiO2 composite byproduct, which could be used as a catalyst for a reverse water-gas shift reaction (RWGS) reaction, a photocatalyst for a Cr(VI) photo-reduction, and a crystal nucleus for chemical plating. The photo-deposition process of Cu(II) with TiO2-500 under UV light was found to be divided into three stages: an initial stage for acceleration through sensitization, a middle stage for a constant rate, and a final stage for deceleration through the slow mass transfer of the diluted Cu(II). After treating the wastewater to the discharge standard, only Cu(0) was observed on the TiO2 surface, which can be employed as a valuable byproduct. The RWGS reaction can be effectively catalyzed by the Cu(0)/TiO2-500 with a 26.78% CO2 conversion and 100% CO selectivity at a temperature of under 600 degrees C. The photocatalytic performance of TiO2-500 is enhanced with the deposited Cu, shortening the time required to photo-reduce the Cr(VI) pollutants. Ni-Cu nanoparticles are also prepared from the sensitization effect of the deposited Cu, forming a bimetallic site as a possible catalyst. This study demonstrated a promising economic process for environmental protection and waste recycling.