Copper oxide (CuO) nanoparticles (NPs) were decorated on reduced graphene oxide (rGO) through the effective synthetic route method. Powder X-ray diffraction, Fourier transform infrared, ultraviolet-visible absorption, and scanning electron microscopy techniques were used to analyze the chemical structure, functional groups, absorbance, and morphology. Under visible light illumination, the CuO/rGO nanocomposites have higher catalytic activity compared to the bare CuO NPs which were suitable for degradation of methylene blue (MB) and Congo red (CR) dyes. According to the findings, the CuO/rGO nanocomposites possess excellent photocatalytic efficiency. Thus, the synthesized CuO/rGO nanocomposite is a promising photocatalyst for the deterioration of organic pollutants in water and wastewater treatment.

In this work, CdO/ZnO nanocomposites was synthesised by chemical co-precipitation followed by thermal treatment method, characterised and its photocatalytic activity for the degradation of methylene blue (MB) dye studied. Study of the effects of operational parameters of dye initial concentration, catalyst dose, and pH on the degradation efficiency of the dye was carried out with response surface methodology (RSM) employing the central composite design (CCD) model and that the maximum predicted degradation percentage of the dye obtained was 81.6% at the optimum values of initial catalyst dose, dye concentration and reaction mixture pH of 30 mg, 13 ppm and 10, respectively, under natural sunlight irradiation for a period of 3 h. The measured experimental value at the indicated levels of the factors was 83.14% during the same degradation time and this is in reasonable agreement with the predicted value. Test for reactive radical species showed that HO^. and O₂^-. are engaged in the decomposition process of the dye. Further, the CdO/ZnO nanocomposite catalyst retained its degradation efficiency by about 96% over 4 consecutive cycles, indicating its stability and potential application for practical decontamination of wastewater from toxic organic pollutants.