A Study Of Spinel Ferrite And Its Composite Materials

Nano-materials have caused great interests because of unique nature. As an important part of nano-materials, spinel ferrite nano-materials are widely used in the areas of catalysts and adsorbents. Therefore, the study of spinel ferrite nano-materials is very important.In this paper, spinel structure ferrite MFe₂O₄ (M = Fe, Co, Ni, Zn, Mn) were synthesized by co-precipitation method and characterized by a variety of means. Since the types of spinel ferrite structure are different, the preparation conditions are different. For example, Fe₃O₄ and MnFe2O4 can be synthesized at room temperature directly, however, MFe₂O₄ (M = Ni, Zn, Co) can only be synthesized after sintering (such as sintering at 650℃). The sizes of the final products of ferrite nanoparticles which have certain pore volumes are between 15-30 nm and the specific surface areas are between 30-100 m2/g. As the ferrite materials can be used as drug targets, catalyst carriers and adsorbents, studys of the structures of spinel ferrite and surface properties of nano-materials are of great significance. In these experiments, the acid-base titration with the synthesized ferrite nanoparticles can effectively avoid the impurity in ferrite minerals. Finally, the surface model of reactivity was established and the adsorption equilibrium constants were calculated using an advanced computer software FITEQL. As there exists two cations in the ferrite spinel structure, one of the cations may be substituted by the hydrogen ions in water, which can be studied by acid-base titration experiments to know the stability of metal ions. The results provide an important reference for the heavy metals treatment in the polluted environment.As a basic material of the spinel ferrite, nano-Fe₃O₄ modified with the surfactant sodium dodecyl benzene sulfonate will help us study the surface adsorption property. When the surfaces of nano-Fe₃O₄ have a positive charge, the SDBS surfactant will be adsorped. The adsorption was attributed to the electrostatic action and fit in the Langmuir model. With increasing the concentration of SDBS, the adsorption amount increased until adsorption equilibrium. The adsorption was unstable and desorped easily. Based on the modified nano-Fe₃O₄, magnetic fluid and magnetic microspheres were prepared. With the anionic surfactant SDBS and non-ionic surfactant polyethylene glycol, the prepared magnetic fluid treated with mechanical stirring and ultrasonic dispersion have a solid content of 1%.In the reaction of styrene, butyl acrylate and the above magnetic fluid, the magnetic polymer microspheres formed with magnetic particles content of about 2.8%. In the acid-base titration experiments of the magnetic microspheres, we found that they have buffering capacity. The result was due to internal buffer of nano-Fe₃O₄ particles, which caused the proton reaction. Therefore, adequate hydration can benefit protonation reaction of nano- Fe₃O₄ in the magnetic polymer microspheres. The polymer coating does not stop the penetration of the H+ or OH- ions. The active center number in the magnetic polymer microspheres indicated that the polymer coating did not affect the surface nature of nano-Fe₃O₄. This result provided some useful information for large-scale application of magnetic polymer microspheres.