The Preparation Of Bismuth Heterojunction And Its Photocatalytic Degradation Of Mixed Antibiotics

Photocatalytic technology is considered as one of the most promising technologies for solving energy and environmental problems because of its non-selective oxidation characteristics.The preparation and selection of photocatalysts is the core of photocatalytic technology.Ruthenium-based photocatalysts have attracted wide attention due to their special structure that have a good response to visible light.In our work,the heterojunctions of bismuth titanate,BiOCl and TiO2 was selected as the research object,the photocatalytic materials of ruthenium-based materials were studied from the following aspects,and the catalysts with stronger photocatalytic activitives was selected for the degradation of mixed antibiotics.Using a mixed alcohol of glycerol and ethanol as a solvent,the bismuth titanate/titanium dioxide heterojunctions were synthesized by solvothermal method.The effect of raw material ratio,solvent ratio and calcination temperature on the formation of BixTiyOz/TiO2 heterojunction was investigated.The possible formation mechanism of BixTiyOz/TiO2 heterojunctions was proposed.The four different crystalline heterojunctions synthesized at the same raw material were characterized by the SEM,BET and electrochemical.The results showed that glycerol plays a role in adjusting the hydrolysis rate of bismuth nitrate and tetrabutyl titanate during the alcohol thermal reaction process,to forming precursors with different morphologies,the calcination temperature affects the ratio of Bi2O3 and TiO2 in the calcination process,and the high temperature would promote the volatilization of Bi.Therefore,four BixTiyOz/TiO2 heterojunctions with different crystal structure could be synthesized by adjusting the solvent ratio and the calcination temperature at the same partial stoichiometry ratio.When the volume ratio of glycerol to ethanol was 0.2,the Bi2Ti2O7/TiO2 and Bi2Ti4O11/TiO2 heterojunctions were obtained at the calcination temperatures was 600℃ and 700℃.The Bi20TiO32/TiO2 and Bi4Ti3O12/TiO2 heterojunctions were obtained when the volume ratio of glycerol to ethanol was 0.5 and the calcination temperatures were 500℃ and 600℃,respectively.These four catalysts were superior to pure TiO2 in the degradation of tetracycline hydrochloride(TC).Under the same synthesis conditions,Bi2Ti2O7/TiO2 heterojunction with the same crystal was synthesized by changing the solvent ratio.The structure and morphology of Bi2Ti2O7/TiO2 heterojunctions were characterized by XRD,SEM,BET,UV-Vis and electrochemical tests.As a result,it was found that Bi2Ti2O7/TiO2 heterojunction had different morphologies under the three solvent ratios.Using TC as degradation pollutant,the effects of different morphologies of Bi2Ti2O7/TiO2 heterojunctions on the degradation efficiency of TC under different degradation conditions(catalyst dosage,solution pH and initial concentration)were investigated by orthogonal test.The results showed that the football-like Bi2Ti2O7/TiO2 heterojunction with the larger specific surface area and the wider pore size distribution showed the larger removal rate of TC,after 3h degradation,the removal rate of 0.1 g/L TC reached to 100%.The nanosheet BiOCl and flower-like BiOCl/TiO2 nanocomposites were synthesized by a simple one-step solvothermal method.The crystal structure,morphology and properties of the materials were characterized by XRD,SEM,BET,XPS,UV-Vis and photocurrent response curves.The catalytic properties of BiOCl/TiO2 synthesized under different conditions were investigated by the degradation of TC.As a result,it was found that the BiOCl/TiO2 synthesized by the ethanol had a greater specific surface area and exhibited higher photocatalytic activity than pure TiO2 and pure BiOCl.BiOCl/TiO2 was used to study the degradation of mixed antibiotics of TC and ofloxacin(OFLX).The products with different reaction times for pure antibiotics and mixed antibiotics were determined by LC/MS,and the possible photocatalytic degradation mechanisms of the pure antibiotics and their mixtures were explored.The results showed that between TC and OFLX in a mixture of antibiotics,there have no influence on the main degradation pathway,and were consistent with the path of pure antibiotics,but there was a tendency of selective degradation during the degradation process.The TC were preferentially degraded under alkaline conditions.It promotes the degradation of TC with a certain amount of OFLX,while a certain amount of TC inhibited the degradation of OFLX.