Study On The Preparation Of Bi-based Multi-dimensional Composite And Photocatalytic Degradation Of Antibiotic Drugs

With the significant discharge of antibiotics into the natural environment,antibiotic pollution has become a serious problem and cannot be ignored.To address such issues,the photocatalytic oxidation technology has received tremendous attention owing to green,economic,and effective process.Compared with the traditional titanium dioxide can only respond to ultraviolet light（only 7%of sunlight）,most bismuth-based materials can respond to visible light and are easy to control.However,due to the inherent shortcomings of a single Bi-based photocatalyst,such as the easy recombination of photo-generated charges,its photocatalytic performance is unsatisfactory.To improve the photocatalytic activity,this article starts with the construction of a Bi-based multi-dimensional composite,and explores the process of photocatalytic degradation of typical antibiotics through various characterization techniques and experiments.The specific research contents and conclusions are as follows:1.Bi/BiVO₄ with excellent photocatalytic performance was synthesized partial reduction with Na BH₄.The X-ray diffraction,field emission scanning electron microscope and X-ray photoelectron spectroscopy（XPS）showed that the generation of metallic Bi.The result showed that the formation of metallic Bi was beneficial to the photocatalytic degradation of ciprofloxacin（CIP）under visible light.And the mechanism of improving the photocatalytic performance of Bi/BiVO₄ was explored by Ultraviolet–visible diffuse reflectance spectroscopy（UV-vis DRS）,photoluminescence（PL）spectroscopy,and photocurrent measurements,the presence of metallic Bi is beneficial to improve the separation efficiency of photo-generated charges.In addition,the radical capturing experiments showed that superoxide free radicals and holes were the main active free radicals during the degradation of CIP.Electron spin resonance spectroscopy verified that the existence of metallic Bi can enhance the material’s ability to generate superoxide radicals.Finally,the pathway of CIP degradation was investigated through high performance liquid chromatography–mass spectrometry,and possible degradation mechanism was proposed.2.The Bi₂WO₆/BiVO₄ heterojunction photocatalyst was constructed for the photocatalytic degradation of oxytetracycline（OTC）.The result showed that the construction of heterojunction system was beneficial to improve the degradation efficiency of oxytetracycline compared with the single material.PL spectra and photocurrent response spectra show that the heterojunction system has better separation efficiency of photogenerated charges.Quenching experiments showed that superoxide free radicals and holes were the main active free radicals during the degradation of oxytetracycline.Finally,six intermediates were identified by high-resolution mass spectrometry,and their degradation pathways were inferred.3.Carbon quantum dots（CQDs）were facilely synthesized using alkali lignin as raw materials.Afterward,CQDs/Bi₂WO₆ hybrid composites were synthesized by the hydrothermal method.XPS indicated that CQDs were successfully loaded into the surface of Bi₂WO₆.According to UV-vis DRS,the existence of CQDs made the composites appear obvious absorption band in the range of 400-550 nm.The result showed that CQDs/Bi₂WO₆ had a better photocatalytic degradation of tetracycline（TC）than Bi₂WO₆.PL spectrum and photocurrent response spectrum showed that the addition of CQDs made the CQDs/Bi₂WO₆ have a lower photo-generated charge recombination probability;SO₄^2-had a more obvious inhibitory effect on the photocatalytic degradation of TC.Finally,the radical capturing experiments showed that superoxide free radicals and holes were the main active free radicals during the degradation of TC.