Synthesis Of Novel Bismuth Based Photocatalysts And The Degradation Of Organic Pollutants In Water Environment

Photocatalysis technology as a new pollutant treatment technology with high efficiency,energy saving,no secondary pollution and other advantages,has been widely studied and applied in water pollution control.Fabrication of high-performance visible-light-driven photocatalysts is of great importance for phtocatalysis research.Bismuth-containing compounds have attracted much attention due to their unique electronic structure and excellent visible light absorption properties.In this paper,we constructed BiOBr-based composites,exposed facet BiOCl with oxygen vacancy and doped Bi(OH)3 catalysts,respectively.The obtained catalysts were characterized by various characterization techniques.The optimum photocatalyst was obtained through optimizing experimental parameters,and then applied to the degradation of antibiotics and dyes in water.The degradation mechanism was also discussed.The main contents are as follows:(1)Facile Synthesis of Bi24O31Br10/BiOBr Composite Nanosheets for Visible Light Photodegradation of CiprofloxacinThe Bi24O31Br10/BiOBr composite nanosheets were synthesized through a solvothermal method using Bi(NO3)3·5H2O and cetyltrimethyl ammonium bromide(CTAB)as raw materials,employed triethanolamine(TEOA)as pH regulator.The obtained catalysts were characterized by X-ray diffractometer(XRD),Scanning electron microscope(SEM),Brunauer–Emmett–Teller(BET)measurement,UV-Vis absorption spectrometer.The composition,microstructure and morphology of the catalysts can easily be controlled by tuning the amount of TEOA and the atomic ratios of bromide and bismuth in the reaction system.The photocatalytic activity of the obtained catalysts was evaluated by the degradation of colorless antibiotic agent ciprofloxacin(CIP)under visible light irradiation(λ≥420 nm).When the amount of TEOA was 8 mL and the molar ratio of bromide and bismuth source was 1.0,the obtained composite Bi24O31Br10/BiOBr exhibited the highest photocatalytic activity.Its reaction rate constant is about 4.0 times higher than that of pure BiOBr,which is mainly attributed to the charge transfer between BiOBr and Bi24O31Br10.Moreover,the high specific surface area and the abundant oxygen vacancies also contribute to the high photocatalytic activity.(2)Additive dependent synthesis of bismuth oxybromide composites for photocatalytic removal of the antibacterial agent ciprofloxacin and mechanism insightBismuth oxybromide composite photocatalysts were synthesized by solvothermal synthesis,applying triethanolamine(TEOA),sodium hydroxide(NaOH)and ammonium hydroxide(NH3·H2O)as the additives,which were denoted as S-TEOA,S-NaOH and S-NH3,respectively.The obtained catalysts were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS),electron spin resonance spectrometry(ESR),Brunauer–Emmett–Teller(BET)measurement,and UV-Vis absorption spectrometry.The results showed that the composites consisted of the same phases containing BiOBr and Bi24O31Br10,and possess different structures,morphology and optical absorption properties depending on the additive.Their photoactivities were evaluated by degradation of ciprofloxacin(CIP)under visible light(λ ≥420 nm)irradiation.The apparent rate constant value of S-TEOA is 2.62 and 4.17 times higher than that of S-NaOH and S-NH3.The possible formation mechanism of the sample S-TEOA and adsorption mode of CIP species on the prepared samples are discussed on the basis of the experimental results.(3)Microstructure modulation of highly active BiOCl nanosheets and photocatalytic degradation of ciprofloxacin under visible light irradiationBiOCl nanosheets with oxygen vacancies on the exposed {010} facets were assistant-synthesized by triethanolamine(TEOA)via hydrothermal method.We in detail explored the surface properties,crystal structure,morphology and optical absorption ability of the prepared catalysts via various characterization technologies.The results indicate that the morphologies and microstructures of the obtained catalysts depended on amount of TEOA.Addition of TEOA induces the production of oxygen vacancy on the surface of the catalysts.Therefore,the synthesized catalysts with TEOA-assistance hold higher photoactivity for degradation of colorless antibiotic agent ciprofloxacin(CIP)under visible light(λ≥420 nm).The obtained catalyst by adding 20 mL TEOA exhibits the highest photocatalytic performance.It is nearly fourteen times as high as that of the catalyst prepared without TEOA and four times as high as that of the catalysts prepared with NaOH or NH3·H2O.The possible degradation mechanism was also discussed on the basis of the experiment results.(4)Facile synthesis of Zn doped Bi(OH)3 catalysts and its enhanced visible light photocatalytic activityIn this study,Bi(OH)3 doped with different contents of zinc were successfully prepared via a facile solvothermal approach and characterized by various characterization technologies.The photocatalytic performance of the obtained catalysts was evaluated by degradation of Rhodamine B(RhB)under visible light irradiation(λ≥420 nm).The results revealed that Zn doping changed the energy band structure of the catalysts and caused upward band bending.Accordingly,the adsorption capability of the catalysts was enhanced.The transfer rate of photogenerated carriers was improved and the recombination of carriers was inhibited.When the optimum Zn/Bi molar ratio was 0.02,the reaction rate constant of the obtained catalyst was as 5.0 times high as that of pure Bi(OH)3.Active species experiments demonstrated that photogenerated holes played a key role for degradation of RhB.The possible carriers transfer route was discussed on the basis of the experiment results.