Photocatalytic antibiotic degradation in coated open microchannels by applying 2D and 3D flow modeling with kinetics

Abstract

The accumulation of active pharmaceutical ingredients in the aqueous environment is a serious problem that will become even more important in the future. In this work, the photocatalytic degradation of ciprofloxacin (CIP) in aqueous solution was assessed over P25-TiO2-coated open microchannels with gravity-driven flow under UV-A irradiation. The deposition of different amounts of TiO2 was carried out via a facile, self-developed procedure. The degradation kinetics of ciprofloxacin was described via the Langmuir-Hinshelwood mechanism. Since the flow characteristics in the microchannel have influence on the mass transfer, the coupled momentum and mass conservation law was solved numerically in MATLAB (2D case) as well as in ANYS Fluent (2D and 3D cases). Although the implemented 2D model in MATLAB allowed the preliminary estimation of the selected kinetic parameters – namely adsorption constant and the specific Langmuir-Hinshelwood rate constant, the sensitivity of the model was not satisfactory which was attributed to the empirical correlations used for the estimation of the external mass transfer coefficient. The 2D and 3D models in ANSYS Fluent predicted efficiently the outlet concentration of ciprofloxacin for different inlet CIP concentrations and liquid phase flow rates. Therefore, the as developed 2D and 3D models in ANSYS Fluent can be used for the design of reactors containing coated microchannels with gravity-driven flow for photocatalytic degradation of active pharmaceutical ingredients.