UVA/TiO2–ZnO–NiO Photocatalytic Oxidation Process of Dye: Optimization and CFD Simulation

In the present study, the sol–gel method is used to synthesize pure TiO2, TiO2–ZnO and TiO2–ZnO–NiO (TZN) nanoparticles. The study aims at investigating the photocatalytic efficiency of the synthesized nanoparticles used in order to remove methyl orange (MO, as a model water pollutant) dye, as exposed to black light radiation. Moreover, it also addresses the factors that may positively or negatively affect the efficiency of the photocatalytic process. XRD, SEM and DRS analyses were used to determine the nanocatalysts’ properties. The response surface method (RSM) was used to investigate the effect of four operating parameters [including the catalyst loading (TZN), basic dye concentration, pH and H2O2 concentration] and optimize the photocatalytic process of MO dye degradation in 60 min. Maximum dye removal percentage was obtained under the best operating conditions (catalyst loading = 0.3 g/l, dye concentration = 15 mg/l, pH 3 and H2O2 concentration = 15 ml/l). The high correlation coefficient (R2 = 0.9930) showed that there is an acceptable level of consistency between the experimental data and the resulted MO dye degradation predictions using the response surface model. Appropriate modules were used to carry out the two-dimensional steady-state computational fluid dynamic (CFD) simulation of the advanced oxidation process in the photocatalytic reactor. A quasi-first-order kinetic equation derived from the Langmuir–Hinshelwood model (kapp = 0.015 min−1) was used to account for the photocatalytic process of MO dye degradation. The value of R2 = 0.8865 indicated the significant consistency between the simulated CFD concentration values and experimental data.