Research On Photocatalytic Degradation Of Organic Pollutants By MgFe₂O₄-based Nano-composites

The rapid development of science and technology has brought many conveniences to people’s clothing,food,housing and transportation,but at the same time,it has also caused immeasurable negative impacts on the ecological environment.With the increasing popularity of dye production and application,the wastewater discharged from the printing and dyeing industry will seriously pollute the water environment and cause great harm to animals,plants and human health.Printing and dyeing wastewater has the characteristics of many types,large amount of water and high organic content.The commonly used treatment methods include physicochemical method,biochemical method,chemical method and combined process.The photocatalytic technology developed in recent years is green,non-toxic,and can completely degrade organic pollutants,and is a potentially effective method for treating dye wastewater.In this paper,magnesium ferrite-based composite nanomaterials were constructed by wet chemical method.The morphology,structure and spectral properties of the materials were characterized by various modern instrumental analysis methods,and their photocatalytic degradation performance on simulated dye wastewater was investigated.The main findings are as follows:（1）Nanometer MgFe₂O₄ materials were prepared by hydrothermal method and solvo-thermal method.The material prepared by solvothermal method has a spherical morphology with a diameter of about 300 nm,and the particle distribution is more uniform,the particle size is smaller,and the yield is higher than that of the hydrothermal method.Both the XRD and FTIR spectra of the samples show the characteristic peaks of spinel-type MgFe₂O₄.Photocatalytic degradation experiments show that the material has a good degradation effect on methylene blue solution under ultraviolet-visible light irradiation.（2）A new type of BiOCl/MgFe₂O₄ composite nanocatalyst was prepared by one-step method.The surface of MgFe₂O₄ nanospheres was wrapped by sheet-like BiOCl.The results of XRD,XPS,DRS and FTIR analysis showed that the two materials were successfully composited.Photocatalytic degradation experiments show that the BiOCl/MgFe₂O₄composite with a mass ratio of 15%has the highest photocatalytic activity;its dosage is 0.05g,and the degradation rate of 5 mg/L methylene blue solution at p H=11 under UV-visible light irradiation 90.7%;after 5 times of recycling,the degradation rate of the dye solution is still more than 85%.（3）A new type of Ag-Ag Br/MgFe₂O₄ composite nanocatalyst was prepared by deposi-tion-precipitation method.SEM and TEM images showed that rice-like Ag-Ag Br was distributed on the surface of MgFe₂O₄ nanospheres.XRD,EDS,XPS and FTIR analysis resu-lts showed that Ag-Ag Br and MgFe₂O₄ good compounding.Photocatalytic degradation experiments show that the Ag-Ag Br/MgFe₂O₄ composite with a mass ratio of 20%has the highest photocatalytic activity;its dosage is 0.05 g,and the visible light degradation rate of 5mg/L Rhodamine B solution at p H=12 is 98.6%;after 5 times of recycling,the degradation rate of the dye solution is still more than 90%.