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UBC Theses and Dissertations

Photocatalytic oxidation of volatile organic compounds (VOCs) in air using ultraviolet light-emitting diodes (UV-LEDs) Rouhani Anaraki, Shahriar


The recent emergence of ultraviolet light-emitting diode (UV-LED) technology has created a promising source of UV radiation available for photocatalytic air purification. Compared with UV lamps, UV-LEDs are compact and provide more flexibility for the design of photocatalytic reactors. Given the new reactor design opportunities, it is necessary to develop a model that can provide insight into the performance of UV-LED photocatalytic reactors. The model can be applied to the design, optimization, and scale-up of UV-LED air treatment units. It is also necessary to examine the effect of photocatalyst properties and the key operating parameters on the overall performance of the reactor. In this study, a computational model was developed to predict the photocatalytic oxidation of gaseous toluene, as a model organic compound, in a UV-LED reactor operating with a titanium dioxide (TiO₂) photocatalyst. To simulate the overall reactor performance, the fluid flow, mass transfer, radiation, and kinetics were modelled using computational fluid dynamics (CFD) software. The kinetic parameters were estimated experimentally and were defined in the model. The model could reliably predict the reactor’s performance, showing results in agreement with the experimental data within the range of studied photocatalyst orientation, flowrates, and UV irradiances. The experimental data and simulation results both showed small mass transfer limitations even at the lowest examined flow rate (Re = 1,125). The modelling results identified the areas of the highest mass transfer limitation using the local values of velocity and concentration. The developed model can be applied to virtual prototyping as well as the design and optimization of UV-LED air purification reactors. Further, it was shown that immobilizing the catalyst on the porous substrate could significantly improve the photocatalytic activity compared with the one on a solid substrate. It was also observed that photocatalytic activity sharply declined after five consecutive photocatalytic tests. The adsorbed intermediates of toluene photocatalysis were identified, and the deactivation mechanism was proposed. It was shown that the radiation of the UV-LED could effectively regenerate the deactivated photocatalyst. Overall, it was concluded that the UV-LED reactor with a TiO₂ on porous support provides an effective method for practical air purification applications.

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