Turning Waste to Resource: An Example of Dehydrogenation Catalyst Cr/ZrO2 Derived from Photoreduction Treatment of Chromium-Containing Wastewater with ZrO2

This work presents a strategy to convert the Cr(VI) pollutant in wastewater into active Cr catalysts in one step by simultaneous photoreduction and deposition using ZrO2 nanoparticles as the photocatalyst and support. Both highly dispersed Cr(0) and Cr2O3 were found on the surface of the resultant Cr/ZrO2 catalyst after UV irradiation. After photoreduction treatment, no residual chromium was detected in post-treated water. The resultant Cr/ZrO2 was found to be an active catalyst for selective dehydrogenation of ethane. It is slightly more stable and active than that prepared by the impregnation method. The interconversion between the structures of Cr–O–Cr and Cr═O should be the active site for oxidative dehydrogenation of C2H6 with CO2. An ethylene yield as high as 17.0% was achieved at 650 °C. This work proved that producing supported metal catalysts from the corresponding metal contaminated wastewater via proper one-step procedure, such as photoreduction treatment, is a feasible strategy to meet the ever-increasing stringent environmental requirements with better economic efficiency.