Preparation Of Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH And Study On The Performance Of Photocatalytic Degradation

Semiconductor photocatalysis as a sustainable green technology can realize the use of solar energy for environmental purification and renewable energy production,which is a good technology for environmental protection and energy development.Bismuth-based semiconductor photocatalysts with high visible light absorption capacity have received much attention due to their unique electronic properties and optical structure,and Bi₂₈O₃₂（SO₄）₁₀ is one of them.However,the single Bi₂₈O₃₂（SO₄）₁₀ has a wide forbidden band value and a low transfer rate of photogenerated carriers,which leads to the rapid compounding of its photogenerated electron-hole pairs;and the Bi₂₈O₃₂（SO₄）₁₀ nanosheets are easily aggregated leading to their small specific surface area,which reduces the reactive sites and hinders the photocatalytic reaction.In order to overcome these problems and improve its photocatalytic reaction activity,this study introduced water talc-like compounds（LDHs）with larger specific surface area into the system,proposed the strategy of energy band structure matching and morphology modulation,and prepared the semiconductor photocatalyst Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH with S-scheme heterojunction structure by calcination method.The photocatalytic performance of the composites was evaluated by degrading tetracycline and reactive blue The photocatalytic performance of the composites was evaluated by degrading tetracycline and reactive blue dyes,and the structure and photoelectrochemical properties of the photocatalytic materials were investigated by various characterization techniques,and finally the photocatalytic performance of the composites was analyzed and the degradation pathways of four antibiotics were deduced by liquid-mass-coupling techniques.This study will provide a feasible strategy to solve the water pollution and provide a reference for the analysis and detection of antibiotics.The main contents of the paper are as follows:（1）Preparation of photocatalytic materials Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH:Layered NiAl LDH,flake Bi₂₈O₃₂（SO₄）₁₀ and three-dimensional spherical Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH heterojunction photocatalytic materials were prepared by hydrothermal and calcination methods,respectively,and tetracycline（TC）and reactive blue dye（RB-19）were used as degradation substrates to optimize the preparation process of Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH.As degradation substrates,the preparation process of Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH was optimized.By optimizing the doping ratio,reaction temperature and time,the optimal preparation process was obtained:the doping ratio of Bi₂₈O₃₂（SO₄）₁₀ and NiAl LDH was 1:1（w%）,the time of calcination was 3 h,and the temperature of calcination was 500℃.（2）Characterization and analysis of the structure and properties of the photocatalytic material Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH and exploration of the photocatalytic mechanism:XRD and SEM were used to analyze the morphology of the composites,and the successful composite of Bi₂₈O₃₂（SO₄）₁₀ and NiAl LDH was demonstrated from the microstructure;XRD and FT-IR tests were used to show that Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH is consistent with the crystalline shape and chemical groups of Bi₂₈O₃₂（SO₄）₁₀ and NiAl LDH;XPS and EDS characterization were used to demonstrate the presence of five elements,Bi,O,S,Ni and Al,further proving the successful composite of Bi₂₈O₃₂（SO₄）₁₀ and NiAl LDH;UV-vis and PL,etc.The photochemical tests showed that the composite has a larger visible light response range and higher photogenerated electron-hole separation efficiency compared with the monomer;the energy band structures and electron transfer directions of Bi₂₈O₃₂（SO₄）₁₀ and NiAl LDH were determined by Mott-Schottky and XPS tests,and it was deduced that Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH is an S-type heterojunction photocatalytic material,and the formation of heterojunction improves the separation of photogenerated electron-hole pairs,which can effectively promote the redox reaction.（3）Establishment and optimization of high performance liquid chromatography coupled with multi-stage mass spectrometry（HPLC-MS/MS）analytical method:Separation and analysis of four common antibiotic standard solutions of tetracycline,sulfathiazole,ciprofloxacin and norfloxacin in positive ion mode were tested to verify the parameters of linear range,detection limit and precision and applied to the detection of actual water samples.（4）Investigation of antibiotic degradation pathways:The photocatalytic degradation performance of Bi₂₈O₃₂（SO₄）₁₀/NiAl LDH composites for four antibiotics was further investigated by an established HPLC-MS/MS method,and the degradation pathways of the four antibiotics were inferred.