Photocatalytic activity of CdO/ZnO nanocomposite for methylene blue dye and parameters optimisation using response surface methodology

Abstract

ABSTRACT 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.