Study Of Preparation Of Sr₂Bi₂O₅, La-doped Sr₂Bi₂O₅ And Their Photocatalytic Properties

It is difficult for dye effluent to be treated because of its complex component,high chroma,increasing amount and non-biodegradability. Photocatalytic oxidation technology for treating dye effluent has a lot advantages such as high efficiency,facile operation,lower cost and non-secondary contamination,and has attracted more and more attentionsIn the paper,Sr₂Bi₂O₅ and La-doped Sr₂Bi₂O₅ were synthesized with SrCO₃,Bi₂O₃ and La₂O₃ by solid-state reaction.The samples obtained were characterized by X-ray diffraction(XRD),scan electron microscopy (SEM).The photocatalytic activities of the Sr2Bi₂O₅ samples prepared were evaluated by the photodegradation of azo dye acid red G on the catalysts.The results of X-ray and SEM analyses showed that the single-phase, homogeneous microcrystalline Sr₂Bi₂O₅ powders were synthesized successfully at temperature 900℃for a short holding time(4h)in static air.The reflections of the powders obtained were indexed in the orthorhombic space group Pnma[62]with Z = 4 and X-ray cell parameters a = 1.4261nm,b = 0.6172nm,c = 0.7625nm.The samples obtained were with the homogenous distribution of particles.La-doped Sr₂Bi₂O₅ was not changed the structure and the morphology of the compound Sr₂Bi₂O₅ crystal.The influences of the calcining temperature and time of the catalysts, irradiation intensity,the dosage of the catalysts and the initial concentration of acid red G solution on the photocatalytic degradation rate of acid red G were studied.The results showed that the Sr₂Bi₂O₅ sample by solid-state method at 900℃for 4h showed a higher photocatalytic activity than P25-TiO₂.50mg/L of acid red G solution could be decoloured completely by using Sr₂Bi₂O₅ as photocatalyst within 120min under fluorescent irradiating(λ=365nm).The best degradation effect can be obtained when the dosage of the photocatalyst Sr₂Bi₂O₅ is 3.0g/L.The photocatalytic activity of the La-doped Sr₂Bi₂O₅ is slightly higher than that of Sr₂Bi₂O₅ when the doping amount of La and decreases with increasing the doping amount of La.The photocatalytic degradation reactions of acid red G solution on the catalyst Sr₂Bi₂O₅ comply with the first order kinetics equation and could be characterized by L-H equation.The photodegradation mechanisms of acid red G on the catalyst were analyzed by infrared analysis(IR)and ultraviolet-visible light analysis(UV-Vis).In conclusion,the degradation of acid red is as a result of catalyst and irradiation but adsorption action. The effect of La203 doping on the photocatalysis was discussed as well.