Photocatalytic degradation performance and mechanism of dibutyl phthalate by graphene/TiO2 nanotube array photoelectrodes

Graphene loaded TiO2 nanotube array (GR/TNA) photoelectrodes were prepared by using anodization and electrodeposition approaches. The effects of different pH values, anions, bias potentials and electron acceptors on the photocatalytic activity of GR/TNA photoelectrodes in the degradation of dibutyl phthalate (DBP) were systematically investigated. Enhanced DBP removal ratio of 87.9% was achieved by GR/TNA photoelectrodes after 90 min of illumination. As a result, with the increase of initial pH values, the DBP removal ratio was also gradually increased. The addition of anions negatively affect the photocatalytic degradation of DBP by the order of NO3− > HCO3− > SO42− > Cl−. After applying a bias potential of +1.0 V, the highest DBP removal ratio of 98% was obtained. In addition, the presence of electron acceptors, KBrO3, K2S2O8 and H2O2, improved the photocatalytic activity of GR/TNA photoelectrodes. Furthermore, to better understand the underlying pathways in the photocatalytic degradation of DBP, the involved reactive species and produced intermediates were detected and analyzed. The major reactive species involved in this system were testified to be hydroxyl, superoxide radicals and holes by performing trapping experiments. The possible mechanism for the photocatalytic degradation of DBP was also proposed and discussed in detail.