Synthesis Of Bismuth Based Magnetic Composite Photocatalyst And Study On The Removal Of Antibiotic Pollutants In The Environment

With the widely use and even abuse of antibiotics,they continue to release and accumulate into the environment,causing environmental pollution problems and affecting human health.As a new pollutant treatment technology,photocatalysis technology is favored by researchers because of its advantages such as no secondary pollution,energy saving and environmental protection in the treatment of antibiotic wastewater.Bismuth-based photocatalysts,such as BiOBr and BiOCl,have been used to degrade toxic organic pollutants due to their unique electronic structure and excellent photocatalytic degradation performance.However,the application of single-phase catalyst is limited by the problems of short electron-hole lifetime and narrow optical response range.In this paper,two kinds of magnetic composite photocatalysts,Fe₃O₄/chitin/BiOBr and Fe₃O₄/chitin/BiOCl,which can be quickly recycled under external magnetic field,were prepared by using the renewable resource chitin as raw material and combining with Fe₃O₄.By optimizing the experimental parameters,the photocatalysts were analyzed by a series of characterization techniques,and the photocatalytic degradation of ciprofloxacin was studied.Meanwhile,the corresponding degradation mechanism was discussed,which provided a reference for the removal of antibiotics in water and the application of bismuth photocatalysts.The main research contents of this paper are as follows:（1）Preparation and characterization of Fe₃O₄/chitin/BiOBr and degradation mechanism of ciprofloxacin under visible lightThe chitin/BiOBr and magnetic Fe₃O₄/chitin/BiOBr composite photocatalysts with different mass fraction ratios were prepared by solvothermal method.Based on the analysis of the basic characteristics of BiOBr composite photocatalyst,ciprofloxacin was used as the target pollutant to investigate the photocatalytic degradation capacity of BiOBr composite photocatalyst under visible light.15%Fe₃O₄/1.5%chitin/BiOBr for ciprofloxacin solution(20 mg·L^-1)has the best degradation efficiency and the degradation rate was 5.8 times than that of pure BiOBr.The effects of different factors on the photocatalytic degradation efficiency of ciprofloxacin were investigated.The catalytic oxidation mechanism of Fe₃O₄/chitin/BiOBr composite photocatalyst was investigated by radical capture experiment.The magnetic and photocatalytic stability of Fe₃O₄/chitin/BiOBr was evaluated by repeatability tests.（2）Study on the preparation and photocatalytic properties of Fe₃O₄/chitin/BiOClIn order to improve the spectrum response range of BiOCl,chitin/BiOCl with different mass fraction ratio and composite photocatalyst Fe₃O₄/chitin/BiOCl which can be magnetically recovered were prepared by solvothermal method.The photocatalytic activity was studied by the degradation of ciprofloxacin and Rhodamine B under visible light.5%Fe₃O₄/2%chitin/BiOCl had the best degradation efficiency for ciprofloxacin solution(10 mg·L^-1),89.54%,and the degradation rate was 5.1 times than that of pure BiOCl.The influences of different factors on the photodegradation of ciprofloxacin were also discussed.Meanwhile,characterization methods were used to analyze the reasons for the improvement of photocatalyst performance.The main active radicals in the degradation process were investigated by free radical capture experiment.The magnetic recovery and stability of the composite photocatalyst were verified by repeated recycling experiments.