Photodegradation of methylene blue dye on a catalyst mixture (Cu2O and CuO) powder in aqueous medium

Abstract

In this study, a powder of two stable forms of copper oxide (Cu₂O and CuO) was utilized for the photocatalytic degradation of Methylene blue (MB). Various attempts were made to determine the optimal conditions for degradation, including liquid-phase adsorption, initial dye concentration, catalyst weight loading, pH variation, H₂O_2, and NaI concentration. The results demonstrated that the photocatalytic degradation of MB by the Cu₂O-CuO mixture achieved efficiencies of 87.9% and 97.1%, respectively, in the presence of 0.01 M NaI and 2 mL of H₂O₂. A degradation rate of 97.92% was obtained at pH 12 after 2 hours. However, increasing the amount of dye is significantly reduced the degradation rate value, as the dye molecules blocked the light intensity required for photocatalyst activation. Liquid-phase adsorption studies showed that the adsorption efficiency of MB increased as its initial concentration decreased.

Additionally, an acidic medium (pH 2) was found to be optimal for adsorption at 95.69%. The addition of NaI to the reaction medium significantly enhanced the adsorption of MB on the catalyst mixture. In addition, the powder X-ray diffraction (XRD) investigations showed the crystalline system of monoclinic CuO and cubic Cu₂O. The morphological analysis using Scanning Electron Microscopy (SEM) revealed irregular shapes of nanostructures. Furthermore, investigations on the catalyst weight effect were investigated.