Multiphysics computational fluid dynamics (CFD) modelling of diclofenac amide removal by photocatalytic oxidation on Fe-TiO₂/N-TiO₂ thin films microreactor

An improved multiphysics computational fluid dynamics (CFD) model, which couples radiation field modeling, species transport, and kinetics was developed to determine the dark adsorption–desorption (k_ads,m k_ads,n, k_des,m, k_des,n) and apparent reaction rate (k_app) constants for the photocatalytic oxidation of diclofenac amide (DCFA) in a recirculating thin-film micro-slit reactor. The photocatalytic oxidation of DCFA under UV irradiation was investigated by changing the initial concentration (C_o) (0.73–1.7 ppm) and recirculation flow rate (Q) (0.15–3.73 L h⁻¹). The ratio of estimated adsorption–desorption rate constants by fitting the CFD model to experiments were k_ads,m/k_ads,n = 0.45, and k_des,m/k_des,n = 1.5, and k_app varied from 1.08 to 1.68 × 10^-3 mmol m^-3 h⁻¹(W m⁻²)^-0.5 with Q (0.15–3.73 L h⁻¹). The CFD model unveiled the switch from mass transfer to kinetics-controlled oxidation of DCFA. The proposed CFD model can be employed as a rapid and flexible tool for the determination of intrinsic kinetic constants in photocatalytic thin-film MRs in the reaction kinetics regime.