Photocatalytic removal of organic pollutants is a promising pollution treatment technology from the aspect of carbon neutrality. The complex diversity of actual wastewater components, as opposed to single-component systems, can significantly affect photocatalytic mechanisms. In this study, complex pollutant systems were created using various coordinating agents, and the effects of P25 on the photocatalytic removal of methyl orange (MO) in these systems and corresponding photocatalytic mechanism were investigated. The results show that photocatalytic removal of MO by P25 using ligands is significantly more efficient, especial removal of MO by the EDTA-P25 (P-E2.5) coordination system resulted dramatically improved MO removal (97.4% versus 12.3% achieved by pure P25 after 15 min), with the reaction rate improved 23.8-fold. Theoretical calculations show that the effective coordination bonds formed by the coordinating agent and Ti atoms reduce the adsorption energy of P25 for MO. In addition, introduction of the coordinating agent EDTA reduces the transition state energy during the MO degradation process and greatly accelerates the reaction rate, and the conduction band position of the EDTA-P25 coordination system shifts to a more negative potential, which induces to the generation of •O2- for effective MO degradation.
Keywords: Coordination; Degradation mechanism; Methyl orange; P25; Photocatalysis.
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