Synergistic effects of the zeolite support and semiconductor coupling in the enhanced photodegradation kinetics of malachite green and Congo red aqueous mixture

This study investigates the photodegradation of malachite green (MG) and congo red (CR) in an aqueous mixture using the photocatalytic effect of CuO-ZnO supported on clinoptilolite nanoparticles (NCP) under direct illumination from a mercury lamp. FTIR, DRS, TEM, and XRD were used to characterize the samples. The photodegradation activity varied with the amount of CuO and ZnO, and the best activity was observed for CuO9.2-ZnO3.8-NCP, with a crystallite size of 30–50 nm estimated by the Scherrer equation. Typical stretching and bending bands of O-Si-O and O-Al-O have appeared at 108cm−1 cm−1 and 480 cm−1, while CuO and ZnO showed bands at 635 cm−1 and 683 cm−1 in the FTIR spectrum of CuO9.2-ZnO3.8- NCP. The effects of various variables, including the amount of loaded CuO and ZnO, initial dye concentration, catalyst dose, and solution pH, were investigated kinetically using the pseudo-first-order model. Corresponding rate constants were estimated in each case and compared in the text. The optimal values were 0.2 g/L of catalyst and 10 mg/L of each CR or MG dye in the mixture at pH 4.5, resulting in 82% and 92% photodegradation efficiency for MG and CR dyes, respectively. The effects of NaCl, NaHCO3, Na2SO4, and hydrogen peroxide were also investigated, and the results showed a decrease in overall efficiency in their presence, especially at higher concentrations, suggesting the following trend in the relative roles of the reactive species in the CR/MG mixture photodegradation. Photogenerated holes> Photogenerated electrons> hydroxyl radicals> superoxide radicals.