Study On The Preparation Of Hollow TiO₂-Based Heterojunction Photocatalysts Towards Antibiotics Degradation In Wastewater

Titanium dioxide(TiO2),as a typical photocatalyst,can directly utilize solar energy to treat wastewater,exhibiting a significant application prospect.However,TiO2-based photocatalysts cannot realize the efficient removal of refractory organic pollutants(e.g.,antibiotic)under visible light due to the limitation of high recombination rate of photogenerated charge and weak absorption in the visible spectrum,even if the full-spectrum irradiation is used,the complete degradation of antibiotics yet cannot be achieved.Although the construction of TiO2-based photocatalysts with heterojunction can efficiently promote the spatial separation of photogenerated charge and improve light absorption,the existed TiO2-based heterojunctions still present the technical drawbacks of low surface area and few redox active sites.Especially,when constructing heterojunction between TiO2 and metal oxide with strong visible-light absorption(e.g.,a-Fe2O3),energy-level match becomes the bottleneck that limits the preparation of heterojunction photocatalysts with high performance.Therefore,based on the problems of low surface area and few redox active sites of TiO2-based heterojunctions,this dissertation constructs three kinds of hollow TiO2-based heterojunction photocatalysts by introducing hollow/porous structure and confinement effect into the design and synthesis of TiO2-based heterojunction photocatalysts.The main contents of research proposal are as follows1.The construction of hollow confined SiO2-Fe2O3@TiO2 heterojunction and its study on the degradation of antibiotics in wastewater.Using cationic polystyrene sphere(CPS)as template,FeaO3 was ultimately encapsulated in the nanospace between inner hollow SiO2 and outer TiO2 by sequential deposition,preparing hollow confined SiO2-Fe2O3@TiO2 heterojunction photocatalyst.Compared with surface supported photocatalysts(SiO2@TiO2-Fe2O3),the as-synthesized confined photocatalyst not only realizes the energy-level match of TiO2 and Fe2O3,but also overcomes a series of drawbacks such as easy aggregation,dissolution,and deactivation of exposed Fe2O3,Also ensuring that the efficient oxidation reaction can be carried out on the surface of TiO2,thereby avoiding inactivation of the active site by blockage,which results in the complete removal of tetracycline and enrofloxacin under simulated solar light2.The construction of hollow TiO2 with {101}/{001} facet heterojunction and its study on the degradation of antibiotics in wastewater.Using CPS@TiO2 as a support,{101} and {001} facets are co-exposed on the surface of TiO2 hollow spheres by fluorinating outer TiO2 via NaF treatment.The investigation shows that {001}facet holds massive unsaturated 5c-Ti atoms that can generate high density of OH groups in water,promoting the formation of coordination complexes between tetracycline molecule and surface-bound Ti(?)ion,which induces strong visible-light absorption.Subsequently,the photogenerated electrons were injected into the conduction band of TiO2 via ligand-to-metal charge transfer,successfully driving the efficient photocatalytic degradation of tetracycline(?90.1%)under visible light.Additionally,the mechanism of facet heterojunction and visible-driven photocatalytic degradation of tetracycline were investigated with many details and the origin of TiO2 visible-light photocatalytic activity was revealed by using in-situ spectrum method.3.The construction of hollow TiO2/Bi2O3 p-n heterojunction and its study on the degradation of antibiotics in wastewater.After metallic Bi was loaded on TiO2 hollow support using photo-deposition method and the as-synthesized sample was calcinated at high-temperature,preparing the hollow TiO2/Bi2O3 p-n heterojunction.The large difference in fermi energy between p-type Bi2O3 and n-type TiO2 induces strong built-in electric field,which drives the separation and transfer of photogenerated electrons and enhances the injection efficiency from Bi2O3 to TiO2,exhibiting superior photocatalytic activity than traditional heterojunctions and thus realizing the ideal goal of complete degradation of tetracycline under visible-light irradiation.