Preparation Of Bismuth Tantalate-based Nanomaterials And Photocatalytic Properties For Tetracycline Degradation

As one of the broad-spectrum antibacterial drugs,tetracycline antibiotics are widely used in veterinary medicine,human medicine and animal husbandry.However,due to the excessive use and improper treatment,they accumulate continuously.When the concentration of antibiotics exceeds the limit,it may lead to the generation of resistant bacteria,thus cause a serious threat to human health and ecological environment.How to efficiently remove tetracycline in wastewater has become an urgent problem to be solved.Photocatalytic oxidation technology is regarded as one of the most promising technologies for the treatment of refractory organic pollutants due to its strong oxidation capacity,no secondary pollution,mild reaction conditions,fast decomposition rate and broad spectrum.In particular,bismuth-based photocatalysts have drawn great development potential due to their advantage of visible light response and have attracted extensive attention from many scholars.However,the development and application of bismuth-based photocatalyst materials are severely inhibited by the high carrier recombination rate.Therefore,this paper took bismuth tantalate as the research object and tetracycline as the target pollutant.By modifying bismuth tantalate through semiconductor composite,the absorption of visible light was enhanced,the migration and transfer efficiency of electron hole pairs was accelerated,and the photocatalytic activity of bismuth tantalate-based materials was improved.In addition,the morphology,photocatalytic activity,photochemical properties and photocatalytic mechanism of the bismuth tantalate based photocatalyst were studied.The main research contents of this paper include:（1）Ag Cl/Bi₃TaO₇composite photocatalytic material was constructed for the first time using the hydrothermal,depositation-precipitation method for the TC degradation and the crystal structure,chemical composition,morphology,optical properties and photoelectric properties of the samples were characterized and analyzed.The experimental results showed that when the molar ratio of Ag Cl and Bi₃TaO₇was 1:5,the Ag Cl/Bi₃TaO₇nanocomposite exhibited the best quantum efficiency（86.82%）under visible light irradiation,1.69 times and2.38 times of Bi₃TaO₇and Ag Cl respectively.In addition,the photochemical property analysis showed that the separation and transfer efficiency of photogenerated carriers in the composites were obviously improved.Meanwhile,the free radical capture experiment showed that hole（h⁺）,hydroxyl radical（·OH）and superoxide radical（·O₂^-）were the main active species.The improvement of the photocatalytic activity may be due to the Z-scheme Ag Cl/Bi₃TaO₇heterojunction structure,which could accelerate the separation and transmission of charge,enhance the light absorption ability,and retain the strong redox ability of photogenerated electrons and holes.（2）Bi₃TaO₇-Cd S nanocomposites were constructed by two-step hydrothermal method,and the effects of p H value,initial concentration and inorganic salt ion on the photocatalytic activity of Bi₃TaO₇-Cd S nanocomposite were also studied.The results showed that when the mass ratio of Bi₃TaO₇and cd was 1:1,the removal rate of TC reached 91.96%within 180 min of visible light exposure,which were 1.49 and 1.29 times of pure phase Bi₃TaO₇and Cd S respectively.The heterojunction formed by Bi₃TaO₇-Cd S composite catalyst material not only effectively inhibited the photocorrosion of Cd S,but also enhanced the separation and transfer of electron hole pairs.In addition,the results of UV-vis analysis showed that Bi₃TaO₇-Cd S composite decreased the band gap of the composite photocatalytic system and increased the absorption capacity of visible light.