The Study For The Removal Of Tetracycline Hydrochloride With Flake GO/Bi₂WO₆ Photocatalyst Decorated By AgBr Nanoparticles

Recently,antibiotics have been widely used as effective drugs for the treatment of health diseases.However,antibiotics also brought more and more environmental problems.The abuse and random discharge of antibiotics would contaminate groundwater,surface water and other water sources through surface runoff or other ways.If the water pollution caused by antibiotics was not effectively controlled,the residual antibiotics would further affect the microbial loop and do harm to animals and plants through food chain.Antibiotics like tetracycline had high stability and were easy to dissolve.Therefore,traditional techniques like membrane separation and ozonation were difficult to degrade the antibiotics.Comparatively,as a new advanced oxidation technology,photocatalysis had the advantages of low cost,harmless and environmental-friendly.Importantly,photocatalytic technology could remove tetracycline and other antibiotics efficiently.The study was devoted to the synthesis of ternary photocatalytic materials which could efficiently degrade tetracycline hydrochloride.Bismuth tungstate（Bi₂WO₆）was well known for its low price and stability in the removal of organic pollutions.However,poor visible light absorption and fast carrier recombination led to its moderate activity.After continuous exploration,the Z-scheme heterojunction photocatalyst 15%Ag Br/5GO/Bi₂WO₆（15A/5G/BW）composed of Bi₂WO₆nanosheets,graphene oxide（GO）and silver bromide（Ag Br）was successfully prepared by hydrothermal and in-situ deposition methods.Furthermore,the physical,chemical and optical properties of 15A/5G/BW were characterized by X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM）,electrochemical workstation,and so on.In addition,the photocatalytic degradation of tetracycline hydrochloride（TC）by 15A/5G/BW was studied comprehensively.Finally,the mechanism of photocatalytic degradation of TC by 15A/5G/BW was analyzed and discussed by liquid chromatography-mass spectrometry（LC-MS）,free radical experiment,electron paramagnetic resonance spectroscopy and other techniques.Based on the analysis of the characterization results,the conclusions ware obtained as following.The crystal structure of 15A/5G/BW accorded with the crystal structure of the monomers contained in it.And its chemical composition had been further verified by XPS and FTIR.While,the elements and chemical bonds contained in 15A/5G/BW could prove the successful synthesis of 15A/5G/BW.Moreover,the SEM and TEM exhibited the morphology of 15A/5G/BW with the laminated flake material loaded with many uniform Ag Br nanoparticles.And the characteristic lattices of Ag Br and Bi₂WO₆can be accurately found in HRTEM images.Finally,the optical properties of 15A/5G/BW were analyzed in detail.Results of UV-Vis DRS spectra clarified that 15A/5G/BW not only had enhanced visible light absorption ability,but also had a wider absorption range of visible light and more outstanding optical properties.Compared with other materials,15A/5G/BW had the lowest PL fluorescence spectrum,which proved its lowest carrier recombination rate.Furthermore,the photocurrent density of 15A/5G/BW was 1.879μA cm^-2,which was18.07 and 16.93 times higher than that of Ag Br and Bi₂WO₆,respectively,indicating the strong visible light response and high carrier separation efficiency of 15A/5G/BW.By studying the photocatalysis and degradation mechanism 15A/5G/BW,the following conclusions could be drawn.The removal efficiency of TC could reach 84%,and its first-order kinetic constant was 0.0515 min^-1（4.6 times and 3.16 times of Ag Br and Bi₂WO₆,respectively）,which indicated the fast degradation rate.Meanwhile,15A/5G/BW had good degradation performance for other antibiotics except TC,which demonstrated its certain versatility.Besides,15A/5G/BW was suitable for a variety of different p H conditions,and the degradation of TC by 15A/5G/BW in actual water was controlled within 5%,indicating its outstanding practical application prospect.Moreover,the slightly reduced degradation efficiency（about 9.8%）after 4 cycles reflected the relatively good reusability and optical stability of 15A/5G/BW.Additionally,the capture experiment verified that h⁺was the most important group.Finally,the mechanism of charge transfer Z-scheme heterojunction mediated by GO in15A/5G/BW materials was proposed by energy band analysis.In conclusion,the addition of Ag Br nanoparticles in the 15A/5G/BW could broaden the visible light response range of Bi₂WO₆and induce the production of more photogenerated carriers.Moreover,GO as a good electronic conductor could accelerate the separation and transfer of carriers in the ternary composite.Thus,the ternary photocatalyst with efficient degradation of tetracycline hydrochloride was obtained,which had a good application prospect.