Comparative Study of Four TiO2-Based Photocatalysts to Degrade 2,4-D in a Semi-Passive System

In this study, the relative efficiency of four forms of supported titanium dioxide (TiO2) as a photocatalyst to degrade 2,4-dichlorophenoxyacetic acid (2,4-D) in KillexA (R), a commercially available herbicide was studied. Coated glass spheres, anodized plate, anodized mesh, and electro-photocatalysis using the anodized mesh were evaluated under an ultraviolet - light-emitting diode (UV-LED) light source at lambda = 365 nm in a semi-passive mode. Energy consumption of the system was used to compare the efficiency of the photocatalysts. The results showed both photospheres and mesh consumed approximately 80 J/cm(3) energy followed by electro-photocatalysis (112.2 J/cm(3)), and the anodized plate (114.5 J/cm(3)). Although electro-photocatalysis showed the fastest degradation rate (K = 5.04 mg L-1 h(-1)), its energy consumption was at the same level as the anodized plate with a lower degradation rate constant of 3.07 mg L-1 h(-1). The results demonstrated that three-dimensional nanotubes of TiO2 surrounding the mesh provide superior degradation compared to one-dimensional arrays on the planar surface of the anodized plate. With limited broad-scale comparative studies between varieties of different TiO2 supports, this study provides a comparative analysis of relative degradation efficiencies between the four photocatalytic configurations.