| In recent years,the problem of environmental pollution has been serious increasingly.And the content of antibiotics in water increased year by year,especially the content of quinolone even reached 6800 ng/L in the surface water of Bohai gulf area.In order to solve this problem,a new water treatment technology with high effect needed to be developed urgently.Photocatalysis technology is one of the most active water treatment technology recently.Although TiO2 has many advantages as a photocatalyst,its photocatalytic activity is low under visible light so that it is restricted.Niobate bismuth is a new type of semiconductor material with broad band gap,it has excellent microwave dielectric property and photocatalytic activity.The application in the field of photocatalysis and study of mechanism were still in the stage of exploration.In this paper,metallic oxy acid salts BiNbO4 and homologue Bi5Nb3O15 were prepared by hydrothermal-calcining method and hydrothermal method respectively.Using the special properties of CQDs as an advantage,CQDs was composited on the surface of Bi5Nb3O15 with the purpose of improving photocatalytic activity.In this paper,the main contents were as follows:(1)The orthorhombic α-BiNbO4 and triclinic β-BiNbO4 were synthesized with Bi(NO3)3·5H2O and NbCl5 by hydrothermal-calcining method.The results were as follows:the band gap of α-BiNbO4 was 3.71 eV,specific surface area was 30.92 m2/g,and average pore diameter was 16.96 nm;the band gap of β-BiNbO4 was 3.21 eV,specific surface area was 2.71 m2/g,and average pore diameter was 14.29 nm.Compared the photocatalytic activity of α-BiNbO4 and β-BiNbO4 to sarafloxacin under xenon lamp(250 W),it was found that the degradation rate of α-BiNbO4 was higher.The influential factors of the photocatalytic degradation of sarafloxacin by α-BiNbO4 has been discussed.When the initial concentration of solution was 10 mg/L,α-BiNbO4 added quantity was 2.0 g/L,initial pH of solution was 3,xenon lamp(250 W)irradiated for 150 min,the degradation rate of sarafloxacin was 97.37%.The photocatalytic deradation of sarafloxacin accorded with Langmuir-Hinshelwood kinetic model.(2)The carbon quantum dots was synthesised from citric acid and urea by hydrothermal method.The results were as follows:CQDs was amorphous carbon structure without complete and continuous lattice structure.There were abundant hydrophilic groups on the surface of CQDs,it had good dispersity without obvious agglomeration in water.The diameter of CQDs was 5 nm and its particle size distribution was narrow.Because of excellent photoluminescence properties,bright blue fluorescent emission from aqueous solution of CQDs could be easily observed under a UV lamp.When the wavelength of excitation was 333 nm,the wavelength of emission was 438 nm.And the quantum yield of CQDs was 13.39%.The CQDs was of a typical wavelength-dependent PL feature.With the increase of the excitation wavelength,the maximum emission peak position shifted to longer wavelength inordinately,accompanied with remarkable change of PL intensity.(3)The CQDs/Bi5Nb3O15 nanocomposite was synthesised from Bi(NO3)3·5H2O,NbCl5 and CQDs by hydrothermal method.The results were as follows:Bi5Nb3O15 belongs to be orthorhombic system with irregular shape.And it was found that the diffraction peak of CQDs/Bi5Nb3O15 at 28.6 ° began to split into two,it might be because CQDs existing led to lattice distortion of Bi5Nb3O15.The band gap of CQDs/Bi5Nb3O15 nanocomposite was 2.65 eV.The photocatalytic activity of CQDs/Bi5Nb3O15 had been evaluated by degradation of sarafloxacin.When the initial concentration of solution was 10 mg/L,CQDs/Bi5Nb3O15 added quantity was 2.0 g/L,xenon lamp(250 W)irradiated for 150 min,the photocatalytic activity of 3 wt%CQDs/Bi5Nb3O15 nanocomposite was the best and the degradation rate of sarafloxacin was 87.90%.Compared with pure Bi5Nb3O15,the degradation rate increased by 39.52%.The stability experiment showed that CQDs/Bi5Nb3O15 nanocomposite was used after 5 times repeatly and degradtion rate was still 86.95%. |
PDF Full Text Request