Preparation Of TiO₂-Based Heterojunction Photocatalyst And Its Application In Antibiotic Degradation

In recent years,antibiotic has been detected frequently in various water environments and attracted significant scientific attention.Due to the stability of structure and the properties of antimicrobial,conventional sewage treatment processes cannot achieve complete degradation of antibiotics and have limitations for the treatment of antibiotics in the environment.Photocatalytic has been deemed a promising technology for the treatment of subaqueous antibiotics due to it incorporates solar energy as an external driving force and possesses a high mineralization rate of organic pollutants.However,TiO₂,the most promising photocatalytic material for applications,is still subject to poor visible light responsiveness and high electron-hole complexation rates.Therefore,in this paper,the electron-hole separation and bandgap were regulated from the perspective of crystal regulation and elemental doping,and two appropriate narrow bandgap semiconductors were selected to construct heterojunctions with modified TiO₂according to the energy band positions.The synthesized TiO₂-based heterojunction catalysts exhibited excellent photocatalytic oxidation performance.The main research results were shown below:（1）TiO₂ nanosheets with different（0 0 1）crystalline exposure ratios were prepared by a solvothermal method using tetrabutyl titanate as the titanium source and HF as the crystal regulation modulator.Based on the results of the photodegradation performance test on norfloxacin（NOR）,the optimal exposure ratio was selected for the synthesis of the composites.Polymeric carbon nitride（PCN）was synthesized first by stepwise pyrolytic,and then（0 01）TiO₂ was grown in situ on the surface of PCN by solvothermal method.The prepared PCN/（00 1）TiO₂（PCNT）heterojunction composites had intimate contact interfaces and excellent photocatalytic performance.The degradation rate of Norfloxacin（NOR）by PCNT could reach96.7%in 90 minutes under simulated sunlight irradiation,and the first-order apparent kinetic constants were 1.5 and 5.5 times higher than those of single-component（0 0 1）TiO₂ and PCN,respectively.The enhanced photocatalytic activity was mainly attributed to the reduction of bandgap and the formation of S-scheme heterojunctions,which improved the visible light utilization and photogenerated carrier separation efficiency.Besides,the hierarchical 2D/2D nanosheet structure and the built-in electric field formed also sped up the charge transfer at the interface,which effectively reduces the photogenerated carrier complexation probability.Moreover,the appropriate proportion of crystal facets could form crystal face heterojunction,facilitating the separation of photogenerated carriers inside the semiconductor.（2）N-doped TiO₂ nanoparticles were first prepared by the sol-gel method using urea as a nitrogen source,combined with a hydrothermal process.Then the N-TiO₂/Zn In₂S₄（NTZIS）composites with different ratios were prepared by loading N-TiO₂ onto the surface of Zn In₂S₄by the solvothermal method.The layered structure of Zn In₂S₄ improved the agglomeration of N-TiO₂ particles and further increased the responsiveness of the material to visible light.Under visible light irradiation,the NTZIS composites exhibited excellent photocatalytic performance.The photodegradation efficiencies of NTZIS were 2.7,1.6,and 1.9 times higher than those of single-component TiO₂,N-TiO_2,and Zn In₂S₄.In addition to the lowering of the photoexcitation threshold by the introduction of impurity energy levels by N-doping,the improved photocatalytic activity was also attributed to the type-II heterojunction formed between the components,which increased the effective separation of photogenerated electron-hole.Moreover,NTZIS showed excellent degradation performance in surface water matrices under sunlight irradiation,and this work presented a viable solution to the problem of antibiotic contamination.