Synthesis And Photocatalytic Property Of Ferrite Synthesized By Molten-Salt Method

With the rapid development of society, the environmental pollution has become more and more serious problem for all mankind. One of the best choices to control environmental pollution is photcatalytic technology. And the focus is to seek the ligh catalyst. TiO2 as a typical photocatalyst has been widely applied. But its good photocatalytic activity needs the UV light radiation, which limits its application to a great extent. Therefore, to explore the new visible photocatalyst with high activity, such as ferrites, becomes the hot issue. However, it is lack of systematic investigation on ferrites. And pure ferrite is difficult to synthesize. In our work, the ferrites such as BiFeO3, Bi2Fe4O9, ZnFe2O4 have been synthesized by the molten salt method. Bi2O3、Fe2O3 and are ZnO adopted as start raw materials. KNO3-NaNO3 is chosen as molten salt. The synthesis mechanism and visible photocatalytic properties of ferrite powders have been investigated. At last, the photocatalytic mechanism of synthesized ferrite powders has also been discussed.BiFeO3 power has been synthesized by molten salt method through adjusting the molten salt ratio, temperature, hold time, cooling mode and reaction crucible. The phase evolution, morphology and visible photocatalytic properties of BiFeO3 power have been investigated. Almost pure BiFeO3 micrometer powder with molten salt ratio of 1:1,2:1 and 5:1 are synthesized at 700℃ for 10min in traditional ceramic crucible. The results show that KNO3-NaNO3 decreases effectively the synthesis temperature of BiFeO3. The synthesized BiFeO3 powder exhibits excellent photocatalytic activity. After irradiation for 2.5h, the highest degradation of MO solution can reach 96.9% for the BiFeO3 powder with 1ml H2O2 assistant, which is synthesized at 650℃ for 1h with the molten salt ratio of 5:1.Bi2Fe4O9 power has been synthesized by molten salt method through adjusting the molten salt ratio, temperature, hold time and cooling mode. The phase evolution, morphology and visible photocatalytic properties have been investigated. Almost pure Bi2Fe4O9 micrometer power with molten salt ratio of 5:1 is synthesized at 750℃ for 10min.The results show that KNO3-NaNO3 promotes the synthesis of Bi2Fe4O9. The Bi2Fe4O9 powder synthesized by molten salt method has the potential to absorb visible light. The synthesized Bi2Fe4O9 powder exhibits good photocatalytic activity. After irradiation for 5h, the highest degradation of MO solution can reach 88.3% for the powder with 1ml H2O2 assistant, which is synthesized at 750℃ for 10min with the molten salt ratio of 2:1.Effects of the molten salt ratio, temperature, hold time and cooling mode on the synthesis of ZnFe2O4 power have been investigated for the molten salt method. The phase evolution, morphology and visible photocatalytic properties have also been investigated. The pure ZnFe2O4 power is hard to synthesize. The ZnFe2O4 based powder synthesized by molten salt method has the potential to absorb visible light. The highest degradation of MO solution is with 61.9% for the ZnFe2O4 based powder.In conclusion, the three ferrites, which are synthesized by molten salt method, exhibit different morphologies. They have the potential to absorb the visible light. Under the irradiation of natural light, they can degradation the methylene blue. The methyl orange is effectively degraded by BiFeO3 powder with 1 ml H2O2. The highest degradation of MO is 96.9% under visible light irradiation for the powder synthesized by molten salt method.