Study On Preparation And Properties Of Zinc Ferrite Modified By Silver/Silver Halide System

As a narrow band gap semiconductor material,ZnFe₂O₄has excellent stability and visible photocatalytic activity,so it has a broad application prospect in degrading organic pollutants and antibacterial.However,when ZnFe₂O₄was used as photocatalyst alone,its photocatalytic activity is poor.Currently,the photocatalytic efficiency of ZnFe₂O₄is often improved by means of composite and modification.Most of the ZnFe₂O₄photocatalysts are in the form of powder.When treating the organic pollutants in the air,they will be affected by airflow and other external factors,resulting in secondary pollution.Therefore,it is very important for the powder photocatalyst to be effectively fixed on a specific carrier.In this paper,Ag/AgCl/ZnFe₂O₄and Ag/AgBr/ZnFe₂O₄composites were prepared and studied including the structure,morphology and optical properties.Then the as-prepared composite materials were deposited on the surface of modified ACF for degradation of gaseous benzene series.The main research contents are as follows:1.ZnFe₂O₄particles were prepared by hydrothermal method,and Z-scheme Ag/AgCl/ZnFe₂O₄photocatalyst was prepared by surfactant-assisted and photoreduction method.The effects of different Ag NO₃content and photoreduction time on the structure and performance of Ag/AgCl/ZnFe₂O₄were studied.The results showed that Ag/AgCl/ZnFe₂O₄exhibited better photocatalytic performance than pure ZnFe₂O₄and Ag/AgCl.With the increase of Ag NO₃content,the photocatalytic performance of Ag/AgCl/ZnFe₂O₄increased first and then decreased.When the content of Ag NO₃was 0.9 mmol,the degradation rate of MO solution by Ag/AgCl/ZnFe₂O₄was up to 86.5%.When the photoreduction time was 60min,the photocatalytic degradation rate of Ag/AgCl/ZnFe₂O₄was as high as 92.4%.After four cycles,the degradation efficiency of MO was still more than 70%,showing better stability than Ag/AgCl.On the basis of the trapping experiment,a Z-scheme photocatalytic degradation mechanism was proposed:Ag/AgCl/ZnFe₂O₄can make full use of the SPR effect of Ag to accelerate the separation of photogenerated electron-holes and prolong the life of the carriers.Finally,it can improve the photocatalytic performance of Ag/AgCl/ZnFe₂O₄under the double effect of·OH and h⁺.2.Ag/AgBr/ZnFe₂O₄nanocomposites were prepared via simple solvothermal method combined with precipitation-deposition and photoreduction,and it was studied for different mass ratio of Ag NO₃/ZnFe₂O₄on structure and photocatalytic performance.Finally,the magnetic recyclability of Ag/AgBr/ZnFe₂O₄was verified and the corresponding photocatalytic mechanism was proposed.The results showed that Ag/AgBr/ZnFe₂O₄nanocomposites prepared with different mass ratio of Ag NO₃/ZnFe₂O₄showed better photocatalytic performance than Ag/AgBr and ZnFe₂O₄.When the mass ratio of Ag NO₃/ZnFe₂O₄was 20%,Ag/AgBr/ZnFe₂O₄showed the best photocatalytic activity,and the degradation rate of MO was 94.6%after 120 min under visible light irradiation.The degradation rate of MO was still 90%above after four cycle experiments.The samples in aqueous solution can be retrieved easily by adding a magnet in order to reduce pollution of powder.The·O₂^-and h⁺were found to play important roles in the photocatalytic degradation of MO.On this basis,the mechanism of Ag/AgBr/ZnFe₂O₄in the degradation of MO under visible light was proposed,and the reason for the increase of photocatalytic performance was attributed to the enhanced visible light utilization and effective transfer of photogenerated charge caused by the relative band gap position.3.The Ag/AgX/ZnFe₂O₄（X=Cl,Br）composites prepared above were deposited on the surface of the ACF,which was modified by PDA,to study the degradation effect for the gaseous benzene series.The results showed that the photocatalytic performance for p-xylene and ethylbenzene after Ag/AgCl/ZnFe₂O₄powder photocatalyst was deposited on the surface of modified ACF was much better than that of pure ACF and the sample prepared by simple impregnation method.At the same time,with the increase of the content of Ag/AgCl/ZnFe₂O₄deposited on the surface of modified ACF,the photocatalytic properties for p-xylene and ethylbenzene increased first and then decreased.When the addition amount of Ag/AgCl/ZnFe₂O₄was 0.1 g,the degradation rate for p-xylene and ethylbenzene were the highest,which were 72.7%and 64.1%,respectively.Then,Ag/AgBr/ZnFe₂O₄powder photocatalyst was deposited on the surface of the modified ACF successfully,and it was found that when the initial concentration of the benzene series increased from 1μL to 7μL,the degradation rate of benzene was continuously increased.For toluene,the degradation rate peaked at the concentration of 5μL.Finally,the possible degradation pathways of toluene were discussed according to the detected final products:the toluene was degraded started from the dehydrogenation of methyl,and gradually opened the ring under the action of active free radicals until decomposed into small molecules.