Fabricated CuO–ZnO/nanozeolite X heterostructure with enhanced photocatalytic performance: mechanism investigation and degradation pathway

Highlights: • Increased photoactivity of coupled copper oxide-zinc oxide/nanozeolite X whit respect to monocomponent one. • Effect of ZnO doped onto nanozeolite X was investigated. • CCRD is used to optimize the effects of independent variables at four levels. • Detection of methyl orange intermediates based on GC-Mass analysis. ZnO-CuO/Nanozeolite X catalysts (ZC/ZXN), coated using different amounts of copper and zinc loading, were synthesized to enhance the photocatalytic activity ZnO in the photo-degradation of Methyl Orange (MO). The catalysts is characterized by XRD, FT-IR, DRS, SEM, and EIS techniques. Owing to the effective mole ratio of the semiconductors in the hybridized photocatalysts, the resulting showed the photo-catalyst containing 12.3 wt% CuO and 3.7 wt% ZnO/ZXN (ZC₄/ZXN) can create excellent degradation ability. Mott–Schottky plot in (Na₂SO₄, 0.1 M) medium indicates p-n junction with a flat band potential of 0.56 and 1.26 eV Ag/AgCl for ZnO and CuO, respectively. EIS measurements showed the values of R_CT 27.9 Ω for ZC₄/ZXN. A lower charge transfer resistance of ZC₄/ZXN is indicative of recombination suppression by improved charge transport to the solution. Response surface methodology (RSM) was selected for optimization and investigation of the combined variables and interaction effects. The quadratic model was well fitted to the experimental data (with values of 0.9824 and 0.9619 for R² and R²adj). Based on the experimental design results, the photodegradation of MO was mostly affected by the variables of pH, catalyst dosage, initial dye concentration, and irradiation time, respectively. The degradation compounds formed during the photo-degradation process were analyzed by the GC–MS technique. During the degradation, MO was converted to benzene sulfonic acid, N, Ń-dimethyl-p-phenylenediamine, etc.