Study On The Degradation Of 4-acetaminophen By Surface Modified TiO₂ Photocatalyst

4-acetaminophen（APAP）is a widely used painkiller and a typical organic pollutant in water.The products of incomplete degradation of APAP have biotoxicity and bioaccumulation in the environment,which seriously threaten human health and life.Therefore,the disposal of APAP is an urgent problem in the field of environment.Photoelectrocatalytic degradation of organic pollutants is a promising approach for contaminant treatments,in which semiconductor catalysts have been widely studied.TiO₂is one of the most commonly used materials in photoelectrocatalysis,which has the advantages of high stability and activity.However,the photocatalytic activity of TiO₂is limited due to poor interaction with pollutants and difficulty for surface active species reacting with organic molecular directly,which is mainly caused by surface hydrophilicity of TiO₂.In this paper,we develop the photoelectrocatalyst system with highly efficient based on TiO₂,and use modification methods to construct different surface modification of TiO₂.Based on the TiO₂catalyst system,we investigate the relationship between the surface modification of catalyst and catalytic degradation reaction activity.The research content mainly focuses on the following two aspects:（1）TiO₂nanowire array was grown on the FTO substrate by hydrothermal method,and then the surface of TiO₂was modified by impregnation method.The experimental results show that the degradation and mineralization performance of TiO₂on APAP can be dramatic improved by appropriate F modification,from 77.9%degradation and 8.9%mineralization of unmodified TiO₂to 80.6%degradation and35.2%mineralization of F modified TiO₂.Further experiments show that the modification of F significantly reduces the recombination efficiency of carriers and improves the photoelectric activity of catalyst.Meanwhile,the introduced F replaces the surface lattice oxygen of TiO₂,and the key active species in the degradation process change from hydroxyl radicals to holes,thus realizing the modulation of the degradation mechanism in the reaction.This work investigates and highlights the effect of surface modification on the charge separation and surface reaction process.（2）TiO₂nanotube arrays were prepared by electrooxidation method on Ti network.The experimental results show that the metal mesh substrate significantly improves the degradation（92.6%）and mineralization（42.3%）efficiency of APAP.The degradation performance of catalyst is further improved by using ammonium hexafluorosilicate to modify the hydrophility TiO₂surface to hydrophobicity,achieving 96.1%degradation efficiency and 61.6%mineralization efficiency.Further experimental results show that the hydrophobic modification dramatic improved the photoelectric activity of the catalyst.Meanwhile,the results reveal that the hydrophobic modification acts on the hydroxyl group on the catalyst surface,and the degradation process is dominated by the hydroxyl radical in the solution phase rather than the hydroxyl radical on the catalyst surface.After hydrophobic modification on the surface of TiO₂,the diffusion of active species from the catalyst surface to the solution phase is realized,which facilitates the efficient degradation of persistent pollutants.This work highlights the effect of hydrophobic modification on the diffusion of surfactant species.