Study On The Preparation Of Porous TiO₂-based Heterojunction Photocatalysts Towards Antibiotics Degradation In Wastewater

With the needs of human society production and life,a large amount of antibiotic pollutants are discharged into global water bodies every year,and it can be detected in surface water,groundwater and even drinking water.However,the traditional sewage treatment process cannot completely remove it,and because of its stable chemical structure and non-degradable characteristics,it poses a huge threat to the ecosystem and human health.Therefore,in addition to the prudent use of antibiotics,there is an urgent need to develop efficient environmental remediation technologies.As an environmentally friendly technology,photocatalysis has very broad prospects for removing antibiotic pollutants from water bodies.However,the disadvantages of the existing photocatalysts such as weak absorption of visible light,low photogenerated electron/hole separation efficiency,and complex preparation process,severely limit the practical application of photocatalysts in degradation of antibiotics.Therefore,it is of great practical significance to seek a photocatalytic technology that can completely remove difficult-to-degrade organic pollutants in water bodies.In this thesis,in view of the current inability to completely degrade tetracycline pollutants in water under visible light and the complex preparation process of the catalyst,a heterojunction photocatalyst based on titanium dioxide（Ti O₂）was designed and prepared.Through the regulation of semiconductor energy levels,the simplification of preparation schemes,and the study of visible light degradation antibiotics,the ideal goal of complete degradation of tetracycline pollutants under visible light has been successfully achieved.On this basis,the one-pot synthesis of the visible light catalyst is further realized,which effectively solves the complex challenges of the existing visible light catalyst preparation process.The specific research content is as follows:（1）In order to solve the problem of low energy conversion efficiency in the visible light region of semiconductors,copper oxide with strong visible light absorption is introduced and a hollow Cu O/Ti O₂ heterojunction photocatalyst is constructed with Ti O₂.That is,using hollow Ti O₂ as a carrier,using light deposition of metal copper and subsequent air calcination to support Cu O particles on its surface to form a heterojunction.Due to the presence of Cu O,the synthesized catalyst is beneficial to increase the visible light absorption of the catalyst,and the formation of p-n heterojunction is beneficial to the efficient separation of photo-generated charges/holes.Degradation experiments of tetracycline pollutants in water show that the synthesized hollow Cu O/Ti O₂ catalyst achieves a good degradation rate of tetracycline（～91%）under visible light irradiation for 100 minutes,which is significantly higher than that of Cu O（～54%）and hollow Ti O₂（～72%）.The degradation rate of tetracycline under the same conditions.（2）In order to solve the problem that the existing catalyst cannot completely remove the tetracycline pollutants in the water under visible light,a new type of bismuth trioxide（Bi₂O₃）and titanium dioxide(Ti³⁺-Ti O₂)with oxygen vacancies are developed by introducing double visible light absorption semiconductors.Bi₂O₃/Ti³⁺-Ti O₂ heterojunction catalyst.That is,with the hydrothermally synthesized porous Ti³⁺-Ti O₂ as the carrier,Bi₂O₃ particles are supported on Ti³⁺-Ti O₂ by photo-deposition of bismuth and subsequent calcination to form a heterojunction.Due to the visible light absorption of the two semiconductors and the built-in electric field of the p-n heterojunction,the synthesized catalyst greatly improves the separation efficiency of photo-generated charges and the visible light catalytic performance.Tetracycline degradation experiments in water showed that after 200 minutes of exposure to visible light,the tetracycline pollutants were completely degraded（100%）.And after five cycles,the degradation effect of 98% is still maintained.Furthermore,LC-MS was used to determine the visible light degradation path of tetracycline,combined with the photoelectric characterization of the catalyst,to clarify the mechanism of complete degradation of tetracycline pollutants in water under visible light.（3）In view of the cumbersome preparation process of the Bi₂O₃/Ti³⁺-Ti O₂ heterojunction catalyst synthesized in the previous chapter,a one-step hydrothermal method was further designed to prepare the Bi2O₃/Ti O₂ heterojunction catalyst.That is,the Bi₂O₃/Ti O₂ photocatalyst is directly prepared by hydrothermally using tetrabutyl titanate and bismuth nitrate.Tests such as TEM,SEM,EDX and BET show that the synthesized catalyst has a porous structure,a high specific surface area(76.31m²g^-1)and a p-n heterojunction,which is beneficial to improve the photocatalytic activity and photocatalytic activity of the Bi₂O₃/Ti O₂ catalyst.Charge separation efficiency.The degradation experiment of tetracycline in the water body showed that the tetracycline pollutant was completely degraded（100%）after irradiating under visible light for180 min.And after five cycles,the degradation effect of 98%is still maintained,indicating that the synthesized Bi₂O₃/Ti O₂ heterojunction catalyst has high cycle stability and broad application prospects.