Study On The Preparation,Characterization And Photocatalytic Performance Of Calcium Magnesium Ferrite

In recent years,photocatalysis technology has received more and more attentionbecause of its wide application in the field of energy and environmental pollution control.Among them,the photocatalyst plays a very important role.Spinel-type ferrite semiconductor material is a promising photocatalyst due to its narrow band gap（about2.0eV）,good photocorrosion resistance and easy recycling.In this dissertation,co-precipitation method and sol-gel method were used to prepare calcium and magnesium ferrite using chemical reagents and dolomite as raw materials.The obtained samples were characterized using XRD,UV-vis and SEM.The photocatalytic performances were evaluated by degrading methylene blue solution under the visible light irradiation.（1）Sponge-like aggregates of the pure CaFe₂O₄ and pure MgFe₂O₄ samples were obtained using co-precipitation method.The samples display good light absorption from ultraviolet to visible.The band gaps was are in the ranges 1.80 eV².10 eV.After3.5 hours of visible light irradiation,the samples calcined at 700°C had a higher degradation rate for methylene blue,with CaFe₂O₄ samples of 56%and MgFe₂O₄samples of 32%.（2）Five groups of samples with calcium to magnesium ratios of 1:4,2:3,1:1,3:2,and 4:1 were obtained using co-precipitation method.At different calcium-magnesium ratios and calcination temperatures,both CaFe₂O₄ phase and MgFe₂O₄ phase coexist in all samples.The samples show good light absorption from ultraviolet to visible,and the band gaps are between 1.80 eV and 1.95 eV.There is no obvious trends between the photocatalytic performance of the sample and calcium to magnesium ratio.When the calcination temperature is 700℃,the sample with calcium to magnesium ratio of 1:1 is better（43%）;when the calcination temperature is 800℃,the sample with calcium tomagnesium ratio of 4:1 is better（56%）.（3）Pure CaFe₂O₄,pure MgFe₂O₄ and calcium magnesium ferrite samples with calcium to magnesium ratio of 1:1 were prepared by sol-gel method.The samples have good light absorption from ultraviolet to visible,and the band gaps are between 1.77eV and 2.03 eV.The calcium magnesium ferrite samples calcined at 700℃shows a higher degradation rate of methylene blue（46%）.（4）Using dolomite as the magnesium and calcium source,the calcium magnesium ferrite sample was prepared by co-precipitation method.The band gaps of the sample are between 1.84eV and 1.98eV,and it has a good light absorption from ultraviolet to visible.The degradation rate of the sample calcined at 700℃is 42%.