Study On Preparation And Photocatalytic Properties Of Modified Bismuth Ferrite

Bismuth ferrite is a kind of new photocatalyst with narrow band gap ?2.5?2.8eV?and a certain degree of response under visible light. But the bismuth ferrite photocatalyst has some defects: 1, the photogenerated electrons and holes produced by bismuth ferrite have a high recombination; 2, the photodegradation rate of bismuth ferrite photocatalyst is slow; 3, the visible light utilization rate of bismuth ferrite catalyst is relatively low. In view of the above problems, the following researches were carried out:?1? With anhydrous acetic acid as solvent, the pure BiFeO₃ catalyst and Ti-doped Ti-BiFeO₃ catalyst were successfully prepared by sol-gel method. The optimum calcination temperature of pure BiFeO₃ catalyst was 550?. The optimum preparation conditions of Ti-BiFeO₃ catalyst as follows: the calcination temperature is 700?,the doping amount of titanium is 10%, and the ratio of bismuth to titanium is 12:1.Pure BiFeO₃ catalyst and Ti-doped Ti-BiFeO₃ catalyst were successfully prepared with nitric acid as solvent. The optimal preparation conditions of pure BiFeO₃ catalyst using nitric acid as solvent are as follows: the calcination temperature was 550?, the volume ratio of solvent to nitric acid/water was 1:1. The optimal preparation conditions of Ti-BiFeO₃ catalyst using nitric acid as solvent are calcination temperature of 700?, nitric acid/ water volume ratio of 1: 1, titanium doping content of 10% and bismuth-titanium ratio of 12: 1.?2? The structure of the catalyst was characterized by XRD, SEM and UV-Vis diffuse reflection. The photocatalytic activity of the catalyst was tested by using tungsten halogen lamp to simulate the sunlight. The results show that titanium doping can improve the photocatalytic activity of bismuth ferrite and make the absorption band of bismuth ferrite red-shifted. The band gap of bismuth is narrowed. The forbidden band width of Ti-BiFeO₃ catalyst prepared with anhydrous acetic acid as the solvent is about 1.85eV under the optimal preparation conditions. While the forbidden band width with nitric acid as the solvent is about 1.88eV .?3? Photocatalytic degradation experiments were carried out using methylene blue solution as the target, the main influencing factors and the optimum reaction conditions of Ti-BiFeO₃ catalyst in the treatment of methylene blue solution were studied.The main influencing factors were the initial pH value of methylene blue solution, the dosage of catalyst and the initial concentration of methylene blue solution. The optimal reaction conditions were as follows: the initial pH value of methylene blue solution was 11, the catalyst dosage was 2.5 g/L, the initial concentration of methylene blue solution was 10 mg/L. Under the optimum reaction conditions, with Ti-BiFeO₃ catalyst prepared under the optimal condition using acetic acid as solvent, the chroma removal rate of methylene blue solution was 98.99% and the removal rate of COD was 76.96% and the light irradiation is 210 minutes.while the using nitric acid as solvent, the Ti-BiFeO₃ catalyst prepared under the optimum preparation condition was treated with methylene blue solution, the chroma removal rate of methylene blue solution was 94.04%.?4? Kinetic study of methylene blue simulated dye wastewater treatment with Ti-BiFeO₃ catalyst was studied. The kinetics of photocatalytic degradation of methylene blue by Ti-BiFeO₃ photocatalyst was in accordance with the first-order reaction kinetics model: C= C₀ exp(0.006257C₀^-0.05209Q^1.1911t).