Preparation And Application Of Magnetic Ni-zn Ferrite Nanomaterials

Ni-Zn ferrites have many advances of high saturation magnetization,high Curie temperature,chemical stability,low coercivity and large specific surface area,are a kind of advanced significant materials,so they have been applied in the environmental sewage treatment and the biological area.In this dissertation,Ni-Zn ferrites were prepared by the rapid combustion process and the citrate-gel process,and they were characterized by the analysis techniques of XRD,SEM,TEM,BET,and VSM,the applications in the sewage treatment and the biological area were studied,and the main conclusions are as follows:1.Magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles were prepared via the rapid combustion process with absolute alcohol as solvent.It was found that the magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles might be obtained at 400 oC with absolute alcohol of 10 mL,and the volume of absolute alcohol was a key parameter to the properties of the magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles.The effect rule of the absolute alcohol volume on the properties of the magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles was revealed.With the volume of absolute alcohol increasing from 10 mL to 30 mL,the average nanoparticle size of magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles calcined at 400 oC for 2 h increased from 14.9 nm to 18.3 nm,the corresponding saturation magnetization increased from 27.1 Am2/kg to 105.2 m2/kg,and when the volume of absolute alcohol was 15 mL,the specific surface area was up to 69.7 m2/g,the controllable preparation of the magnetic Ni_0.5Zn_0.5Fe₂O₄ nanoparticles by the rapid combustion method was realized.2.The adsoption technology of neutral red onto magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites was optimized by the response surface methodology?RSM?,and the adsorption kinetics and adsorption isotherm were researched.According to the statistical analysis of experimental data by RSM sofeware,the optimization adsorption technologies of neutral red onto magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites were confirmed.pH of the neutral red solution was 5.4,the silica content in nanocomposites was 17.3 %,the calcination temperature for the nanocomposites was 581 oC,and the maximum adsorption capacity of neutral red onto magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites was up to 39.9 mg/g under the optimization conditions.Based on the simulation and calculation of the experiment data,it was found that the pseudo-second-order kinetic model was in a good agreement with the kinetics data for the adsorption of neutral red onto the magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites,and the Redlich-Peterson model could be used to evaluate the adsorption isotherm of neutral red at room temperature,which suggested that the magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites' surfaces were heterogeneous,and the adsorption of neutral red onto the magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites could be a hybrid of monolayer and multilayer absorption mechanism.3.Immobilization of Penicillin G Acylase?PGA?onto magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO2 nanocomposites.The magnetic Ni_0.5Zn_0.5Fe₂O₄@SiO2 nanocomposites were successfully prepared via the rapid combustion process,and their surfaces were modified with glutaraldehyde as the reagent.The penicillin G acylase?PGA?was successfully immobilized on the surface-modified magnetic Ni_0.5Zn_0.5Fe₂O₄/SiO2 nanocomposites,and the activities of the immobilized enzyme and free enzyme under the various conditions were systematically examined.Compared to each other,it was found that the immobilized PGA was affected less by pH and temperature than the free PGA,and the immobilized PGA exhibitted good chemical stability and thermal stability of enzyme catalyst.The relative activity of the immobilized PGA was 63.5% after 12 times cycling,which suggested a good recycling rate of the immobilization of PGA.