Research On Preparation And Application Of Magnetic Ni-Zn Ferrite-based Nanocomposites

Magnetic ferrite nanomaterials are generally characterized by the novel physicochemical properties and excellent performance,such as strong magnetism,large specific surface area,good chemical stability,facile preparation,low toxicity,etc.They can be recovered after the reaction under the external magnetic field and combined with other materials to improve the properties according to the application requirements.Moreover,large specific surface area provides sufficient active sites.Hence,they are considered as nanomaterials with broad developed prospects.This paper studies that Ni-Zn ferrite nanomaterials are compounded with GO,ZnO and Ag,respectively,based on the preparation of them.The application of them in immobilized enzyme,dye degradation and antibacterial are investigated.The main conclusions are as follows:?1?The preparation of magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles.Magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles are prepared by sol-gel method and rapid combustion method with ferric nitrate,zinc nitrate and nickel nitrate as raw materials.According to the experiment results,Under the condition of being calcined 2 h at 400^oC,the particle size and saturation magnetization of the products prepared by the rapid combustion method are 20 nm and 63.7 emu/g,respectively.Under the condition of being magnetically stirred for 24 h,citric acid as the complexing agent and 50%ethanol as solvent at pH of 11,the particle size and saturation magnetization of the products dried at80^oC and calcined at 400^oC for 2 h are 18 nm and 78.3 emu/g by sol-gel method,respectively.The magnetic nickel-zinc ferrite nanoparticles obtained by the two methods show no significant difference in morphology and magnetic properties.However,the fast combustion method has advantages of simple operation and short preparation time.?2?Immobilization of Penicillin G acylase on the magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO₂-NH-GO composites.Magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO₂ nanocomposites are prepared by rapid combustion method,which are modified with amino to obtain the magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO₂-NH₂ nanoparticles.GO is prepared by improved Hummers method.And magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO₂-NH-GO composites are obtained by the modified materials being loaded on GO.According to the experimental results,the Ni_0.5Zn_0.5Fe₂O₄@SiO₂ nanocomposites are successfully coated by SiO₂ to form the shell core structure with the particle size of 20 nm.The modified particles are evenly dispersed on GO.The PGA is adsorbed covalently by Ni_0.5Zn_0.5Fe₂O₄@SiO₂-NH-GO composites with a large number of oxygen-containing functional groups.The optimum immobilization conditions are obtained:enzyme concentration is 10 mg/g and the immobilization time is 6 h.The immobilization binding rate is 91.7%.Compared with the free PGA,the immobilized PGA has better catalytic stability at temperature of 20-60^oC and pH of 6-9.The thermal stability is enhanced at low temperature and the affinity for substrates decreases.Immobilized PGA still maintains 74%catalytic activity after 9cycles.?3?Preparation of magnetic Ni_0.5Zn_0.5Fe₂O₄/ZnO?NZFO/ZnO?nanocomposites and their photocalytic research.NZFO/ZnO-R nanocomposites are prepared by coprecipitation with magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles,zinc nitrate and sodium hydroxide as raw materials.According to the characterization,the NZFO/ZnO-0.2nanocomposites are composed of nanoparticles and nanorods with particle size of 18 nm,rod length and width of 198 nm and 66 nm,respectively.The nanocomposites have a specific surface area of 37 m²/g,pore diameters of 50-300 nm,and a saturation magnetization of 17 emu/g.The absorption spectrum extends from the ultraviolet region to the visible region.The photocatalytic properties of the nanocomposites are studied by degradation of methyl blue.The photocatalytic activity of the catalysts is strongest when the mass ratio of NZFO to ZnO is 1:1,the dosage of the catalysts is 0.2 mg/mL,pH is 11and dye concentration is 5 mg/mL.The degradation rate of magnetic NZFO/ZnO-0.5nanocomposites remains more than 85%after 5 cycles.?4?Preparation of magnetic Ni_0.5Zn_0.5Fe₂O₄@Ag?NZFO@Ag?nanocomposites and their antimicrobial investigation.The magnetic NZFO@Ag-R nanocomposites are prepared by reduction method with magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles,silver nitrate and sodium citrate as raw materials.The antibacterial performances of the materials are evaluated by the growth curve,the inhibition zone test,the MIC test,and the MBC test with E.coli and S.aureus as the bacterial source.The XRD,SEM and VSM characterization results show that the magnetic NZFO@Ag-40%nanocomposites have a spherical morphology with an average size of 23 nm.The Ag loaded has a cubic crystal structure and evenly mixed with NZFO.The mass fraction of silver is 31.34%.The saturation magnetization decreases from 63.7 emu/g to 31.6 emu/g with the increase of Ag content.The antibacterial circle test and growth curve test explain that NZFO nanoparticles have almost no antibacterial properties.When the Ag content reaches 40%,the radius of antibacterial circle is the largest and the inhibition effect of the growth curve is the most obvious.When the content rises to 50%,the antibacterial activity is not significantly enhanced.The MIC and MBC of the magnetic NZFO@Ag-40%nanocomposites for E.coli are 5?g/mL.The MIC and MBC for S.aureus are 5?g/mL and 10?g/mL,respectively.