Simulation of photocatalytic planar microreactor for degradation of cephalexin in contaminated water

The degradation of pollutants in a planar continuous flow photocatalytic microreactor was simulated using COMSOL Multiphysics. The Langmuir-Hinshelwood model was proposed to describe the available experimental data for the reaction kinetics of cephalexin (CEX) degradation from aqueous solution using the Bi2WO6/CNT/TiO2 photocatalyst, and the kinetic constants of this model were evaluated. The predicted results for the breakthrough curves of this pollutant at the microreactor outlet were compared with experimental data. The mean absolute error between the model and experimental values at inlet CEX concentrations of 30, 40, 50, and 60 mg/L was 3.3%, indicating a good model prediction. The parametric study results indicate that increasing the length of the microreactor from 50 to 100 mm enhances the removal efficiency from 82 to 97%. Additionally, reducing the microreactor depth from 300 to 100 µm increases the removal efficiency from 82 to 92%. The calculated Damköhler number under the optimal experimental conditions was 0.42, indicating that the photocatalytic process is primarily controlled by reaction kinetics rather than mass transfer limitations.