Modeling and CFD simulation of photocatalytic removal of tetracycline by ZnO/PbBiO₂Cl nanocomposite catalyst

In this work, the photocatalytic degradation process under visible light in a batch photoreactor was investigated using computational fluid dynamics (CFD). The removal of tetracycline (TC) by the ZnO/PbBiO₂Cl photocatalyst was modeled using the single organic species model based on Langmuir-Hinshelwood kinetics. In addition, the hydrodynamic behavior of the two-phase flow inside the photoreactor was simulated using the Eulerian-Lagrangian approach. In this study, the kinetic of the degradation reaction, velocity field of suspension, and concentration of TC were investigated. Based on the CFD results, it has been determined that a rotational velocity of 250 rpm in the reactor is the optimal speed that leads to the highest homogeneity (approximately 95 %) in suspension. Therefore, more light is absorbed by performing experiments in high-quality mixing, and maximum degradation can be achieved. The kinetic study showed that the degradation rate follows pseudo-first-order kinetics. The effect of different weight percentages of PbBiO₂Cl and various loading of ZnO/PbBO₂Cl on the degradation rate was also examined. The results showed that the 0.5 g/l of ZnO/PbBO₂Cl (40 %) is the optimal amount. The degradation reaction kinetic constant was also calculated about 200 × 10⁻⁴ min⁻¹. Finally, the obtained modeling results demonstrate excellent agreement with the experimental data.