Integrated Approach for Hazardous Cr(VI) Removal: Reduction, Extraction, and Conversion into a Photoactive Composite, CuO/CuCr2O4

Abstract

The present study reports on CuO-assisted reduction of Cr(VI) under ambient conditions using sodium borohydride and its complete removal. The confirmation of the reductive removal of Cr(VI) was assisted by powder X-ray diffraction, Fourier transform infrared, scanning electron microscopy, mic absorption spectro, UV-vis, and UV-vis-diffuse reflectance spectroscopy techniques. The analysis revealed that the process involved adsorption of dichromate ion on the surface of copper oxide, reduction of Cr(VI), and precipitation of Cr(III) as its hydroxide. Cr(VI) reduction capacity of CuO was found to be around 27.2 mmol/(g h). The residue collected showed promising reusability for 3 to 4 cycles, and the exhausted residue was finally converted into a black composite, CuO/CuCr2O4. The composite showed positive response for the photodegradation of methyl orange. Thus, the current protocol proposed a complete package of cost-effective reduction of Cr(VI) to Cr(III), precipitation into its hydroxide, and the conversion of the residue into a photoactive composite.