Study On Preparation,characterization Of Lanthanum Nickel Perovskite-oxidescatalysts And The Photocatalytic Properties Under Visible Light

Discharge of sewage from industry, agriculture and livelihood, not only cause serious pollution to the environment and endangering human health. Therefore, research of the catalysts which can using visible light remove water pollutants has vital significance. Perovskite-type oxides showed high catalytic activity of removal of organic pollutants due to the special structure. In this study, a series of lanthanum-nickel perovskite-type complex oxide catalysts La_1-xM_xNi_1-yN_yO₃?M=Sr?Ca?Ba?Ag,x=0?0.1?0.3?0.5?0.7,N=Co?Cu?Mn?Zn,y=0?0.1?0.3?0.5?0.7? were synthesized by sol-gel method and using citric acid as complexing agent. The prepared precursor and catalysts were characterized by TG-DTA,XRD, UV-vis DRS,PL, BET, SEM and the catalytic activity of the catalysts was evaluated by decolorization rate of methyl orange solution.Moreover, the influence of synthesis conditions on structure and visible light photocatalytic activitys of catalysts were also studied. The photocatalysis conditions on the influence of degradation of basic fuchsin and chlorpyrifos solution were researched, and the catalytic process dynamics were studied.1?The study found that when M, N or M and N respectively doped in A site,B site or AB site codope could get perovskite composite oxides La_1-xM_xNi_1-yN_yO₃?M=Sr?Ca?Ba?Ag, N=Co?Cu?Mn?Zn?in suitable doping concentration. The photocatalytic activities of the La_1-xM_xNi_1-yN_yO₃ catalysts were investigated by photocatalytic degradation of methyl orange under the irradiation of the 500 W xenon lamp. The results indicated that the types of metal ions and doping concentration had an important influence on the photocatalytic properties under visible light,and the La₀.9Sr₀.1NiO₃ showed excellent photocatalytic activity.It showed the types of metal ions and doping concentration were influenced the ability of catalyst absorption and electroic-hole recombination.2?The influence of synthesis conditions?dosage of citric acid, pH, calcination temperature and calcination time? on the crystal structure, electroic-hole recombination, surface appearance and visible light catalytic activity were also discussed and optimized. The results showed that single-phase hexagonal structure La₀.9Sr₀.1NiO3 crystals could be obtained when ratio citric acid and metal ions was 1:1, pH was 1.5, pretreated at 400 ? for 4 hours and calcined at 700 ? for 4 hours. When the catalyst dosage was 1.20 g/500 ml, decoloration rate of methyl orange solution of 13.2 mg/L was up to 62.1% in 180 min under the visible light irradiation.3?Taking basic fuchsin solution as the target pollutant and La₀.9Sr₀.1NiO₃ as photocatalyst, the effects of lighting time,different catalyst dosage, initial concentration of solution, different pH, different dosage of H₂O₂ and catalyst cycle time on the degradation rate were researched.The results showed that the decolourization rate and CODCr removal rate respectively could reach 83.33% and 68.43% at the best catalysis conditions with visible light irradiation 180 min, initial concentration of basic fuchsin is 12.80mg/L, catalyst concentration 1.20g/L, weakly acidic to neutral pH and add 2ml/L hydrogen peroxide. Under this conditions, photocatalytic process following the secondary reaction kinetics, the constant of reaction rate was 0.0025mg-1?L?min-1 and half-life period was 41.28 min. Catalyst reused four times, decolorization rate can still reach 68.43%.4?The properties of catalytic degradation on chlorpyrifos solution have been studied.The several important affecting factors of photocatalytic degradation, including illumination time,different catalyst dosage, initial concentration of solution, initial pH value of solution, different dosage of H₂O₂ and catalyst cycle time, were also discussed. The results showed that the degradation and CODCr removal rate respectively can reach 92.10% and 71.68% at the best catalysis conditions with visible light irradiation 180 min, initial concentration of basic fuchsin was 185.0mg/L, catalyst concentration 2.40g/L, the value of pH was 6.4 and add 6ml/L hydrogen peroxide. Catalyst reused four times, degradation rate could reach 78.28%. Under optimum conditions, photocatalytic process following the zero-order reaction, the constant of reaction rate was 0.5357 mg ? L-1? min-1 and half-life period was 90.26min.