Preparation And Photocatalytic Degradation Performance Of Transition Metal-doped Zinc Oxide

The dye water was an industrial waste. Photocatalytic degradation of dye waste was one of the current research focus. The main difficulty was focus on the preparation of new and efficient catalysts. The ZnO precursor was prepared by hydrothermal synthesis in this paper. On this basis,The transition metal-doped ZnO photocatalyst was respectively prepared through the hydrothermal synthesis method, a chemical deposition method and a light reduction method. The photocatalytic performance of ZnO and M/ZnO(M = Cu, Fe, Ag) were tested by the degradation of methyl orange solution. The influence of different degradation parameters and the best degradation conditions were discussed.(1) The three different sets of reactants were ① Zn(Ac)2·2H2O, NaBH4, NH3·H2O as reactants,②Zn(Ac)2·2H2O, NaOH as reactants and Zn(NO3)2·6H2O,(CH2)6N4 as reactants. The three kinds of ZnO nanoparticles were prepared by hydrothermal synthesis. Known by SEM and TEM, the three kinds of ZnO nanoparticles had better crystallinity. XRD results showed that the three kinds of ZnO nanoparticles all were hexagonal wurtzite structure. The characteristic absorption peaks of ZnO were appeared near 400 nm in UV-visible spectrum. The dosage,exposure time, initial concentration of methyl orange and the initial pH of solution were changed.We obtained that the photocatalytic properties of NO.② ZnO photocatalyst was superior thanNO.①and NO.③ZnO. When the dosage of NO.②ZnO photocatalyst was 1.2 g·L-1, the concentration of methyl orange solution was 0.01 g·L-1, the illumination time was 60 min, the pH of solution was 9, the degradation rate was 81.35% at this time. NO.②ZnO photocatalyst was selected as a photocatalyst precursor to prepare for the next test.(2) M/ZnO(M=Cu, Fe, Ag) photocatalysts were successfully prepared by hydrothermal synthesis. The photocatalysts had high crystallinity. The particle size of photocatalysts were 500 nm. The UV-visible spectrum of M/ZnO had suffered different degrees of redshift relative to pure ZnO. Cu and Fe-doped ZnO were inhibited photocatalytic activity in some extent. When the dosage of Ag/ZnO photocatalyst was 1.2 g·L-1, the concentration of methyl orange solution was0.01 g·L-1, the illumination time was 60 min, the pH of solution was 11, the degradation rate was99.86% at this time. The highest efficiency degradation of the pure ZnO was 81.35%. Comparing with it, the photocatalytic activity of Ag/ZnO had significantly improved.(3) M/ZnO(M=Cu, Fe, Ag) photocatalysts were successfully prepared by chemical deposition method. Comparing with the XRD diffraction pattern of pure ZnO and M/ZnO, the number of diffraction peaks reduced and the width of the diffraction peak changed after doping.Comparing the angular position of the diffraction peaks in the same crystal plane index, we also had found a slight change. Cu, Fe, Ag-doped ZnO could change their crystal growth and crystal structure. When the dosage was 1.2 g·L-1, the concentration of methyl orange solution was 0.01g·L-1, the illumination time was 60 min, the pH of solution was 5.4, the degradation rate ofCu/ZnO or Ag/ZnO were 86.42% or 95.38% at this time.(4) M/ZnO(M=Cu, Fe, Ag) photocatalysts were successfully prepared by light reduction method. The band gap of Cu/ZnO and Fe/ZnO were reduced to 3.13 eV. The band gap of Ag/ZnO was reduced to 3.10 eV. When the dosage was 1.2 g·L-1, the concentration of methyl orange solution was 0.01g·L-1, the illumination time was 30 min, the pH of solution was 5.4, the degradation rate of Ag/ZnO was 92.259% at this time. But the degradation rate of Fe/ZnO onlywas 34.714%.(5) NO.②Zn O photocatalyst was selected as a photocatalyst precursor. M/Zn O(M = Cu, Fe,Ag) photocatalysts were prepared by three methods. Comparing their photocatalytic effect, Ag/Zn O was always optimal. The Ag/Zn O photocatalyst was prepared by the hydrothermal synthesis method, a chemical deposition method or a light reduction method. In the same light catalytic conditions, the Ag/Zn O was prepared by light reduction method. Its photocatalyst performance was optimal.