Three-dimensional CFD modelling of a photocatalytic parallel-channel microreactor

Abstract

This paper presents the estimation of adsorption rate and apparent kinetic rate constants for photodegradation of 4-nitrophenol in a recirculating and single-pass photocatalytic microreactor using simulated solar radiation. The effect of changing initial concentration (Co) of 4-nitrophenol in a recirculation mode was predicted by employing a dynamic transport model with kinetics (momentum and mole transports) using COMSOL Multiphysics. Adsorption and kinetic rate constants were estimated by fitting 3D model to experimental data. The estimated monolayer (m) and multilayer (n) adsorption–desorption rate constants were 1.77x104 m3 mol-1 h−1 (kads,m), 0.0252 h−1 (kdes,m), 1.77x104 m3 mol-1 h−1 (kads,n) and 0.0126 h−1 (kdes,n) respectively; and apparent kinetic constant (kapp) was 2.16 h−1. Results from the single pass model showed that a rise in Co produces an increase in initial degradation rate. Moreover, decreasing flow rate (Q), increasing microchannel length (L) and decreasing microchannel height (h) boost the overall conversion of 4-nitrophenol in solution. This work demonstrates the promising application of microreactors in heterogeneous photocatalysis as tertiary stage technology for wastewater treatment, especially for the photodegradation of recalcitrant pollutant.