Computational fluid dynamics modeling of airlift VUV/UV photoreactor with internal circulation

Ultraviolet (UV) chemical degradation is a low-cost, environmentally friendly, and sustainable wastewater treatment technology. In this study, we designed an airlift photoreactor with internal circulation and explored the effect of its flow characteristics (hydrodynamics) on the reaction to improve the degradation efficiency of pollutants in water. The continuous flow vacuum ultraviolet (VUV)/UV method was used to evaluate the degradation ability of pollutants in the reactor in terms of computational fluid dynamics (CFD), mass transfer, and photoreaction kinetic models. Results show that the turbulence intensity and circulation effect in the reactor are ideal in the range of gas flow rate used in this study, and the chance of UV radiation can be effectively improved. The formation of OH radicals and the decomposition efficiency of methylene blue (MB) in the VUV/UV process is strongly correlated with the mixing strength in the reactor. The computational results of the CFD model are close to the experimental results, but the efficiency of CFD in MB processing is higher than the experimental results. This finding is because the scavenger effect of MB decomposition by-products is not fully considered in CFD kinetic analysis.