Modelling of a recirculating photocatalytic microreactor implementing mesoporous N-TiO2 modified with graphene

Abstract

• Photocatalytic degradation of 4-nitrophenol in microreactor under solar irradiation. • The used CFD model incorporates total recirculation mode of operation. • The CFD model accounts for adsorption in the dark. • The CFD model predicts experimental data in a wide range of reactant concentrations. The use of microreactors in (photo)catalytic processes offers new possibilities for studying and optimizing many mass and photon transfer limited reactions. In this study, we propose a scalable computational fluid dynamics (CFD) model for the prediction of photocatalytic degradation of a model pollutant (4-nitrophenol) using immobilized N-doped TiO 2 grown over reduced graphene oxide (N-TiO 2 /rGO) in a photocatalytic microreactor working in continuous flow-recirculation mode. The mode of operation used in this study allows the reduction of mass transfer limitations inherent to heterogeneous photocatalytic reactions taking place on immobilized catalysts. A CFD model was developed for effective prediction of experimental results using COMSOL multi-physics. The experiment and the model results clearly showed a good agreement. The model parameters were determined through fitting the model with the experimental data, adsorption rate constants were estimated to be 1.76 × 10 4 m 3 mol −1 h −1 and 0.0252 h −1 for monolayer ( k ads,m and k des,m ), 1.76 × 10 4 m 3 mol −1 h −1 and 0.0126 h −1 for multilayer ( k ads,n and k des,n ); and the intrinsic rate constant ( k s ) was 2.02 h −1 . This proposed model herein could serve as a practical tool to improve and optimize an extensive number of photocatalytic reactions for (waste)water applications in microreactors operating in recirculation mode.