Multiphysics modeling of flow-through advanced oxidation photoreactors with in-situ hydrogen peroxide electrogeneration

Advanced oxidation processes (AOPs) commonly use chemicals such as hydrogen peroxide (H2O2) in combination with ultraviolet (UV) radiation to produce hydroxyl radicals (·OH). As supply chain management and storage of concentrated H2O2 is challenging, in recent years, in-situ H2O2 generation systems are gaining attention. These systems are in early stages of research and development, and a numerical model can help accelerate the development of highly efficient systems. In this work, for the first time, we describe a mechanistic multiphysics model to simulate a flow-through electrochemical AOP photoreactor with in-situ H2O2 electrogeneration and UV radiation. The electrochemical, hydrodynamic, radiation, and kinetic phenomena were incorporated into the model. The model showed good agreement with the experimental results over a wide range of flow rates (5% average difference in 35–95 mL min–1) and current densities (9% average difference 7–34 mA cm–2). The computational model was verified with the experimental data obtained for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), and it was applied to study the performance of some design variations in terms of hydrodynamics and radiation. The results showed that implementing reflective walls will increase the UV fluence, which ultimately led to a 45% improvement in the contaminant removal.