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

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 TiO2 grown over reduced graphene oxide (N-TiO2/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 × 104 m3 mol−1 h−1 and 0.0252 h−1 for monolayer (kads,m and kdes,m), 1.76 × 104 m3 mol−1 h−1 and 0.0126 h−1 for multilayer (kads,n and kdes,n); and the intrinsic rate constant (ks) 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.