The Research On Preparation Of Functional Magnetic Nanomaterials And Selective Adsorption Of Rare Earth Ions

Since the industrial revolution,the modern industrial sector has been based on a strong choice of base metals.The properties of these metals can be improved by adding additional metals,so as to obtain a series of different and ideal properties in terms of strength,temperature resistance,ductility and hardness,with a wide range of applications.These additional metals include rare earth elements?lanthanide,scandium?,semiconductor materials and precious metals.In addition to plasticity,ductility and good chemical reactivity,rare earth elements are widely used because of many inherent ideal properties,such as catalysis,optical and magnetism.They don't only show paramagnetic tendency and strong anisotropy,but also play an important role in the development of wind energy,energy-saving light-emitting diode?LED?light source and electric vehicle technology.Some of the other significant advances promoted by rare earth elements are reflected in digital camera lenses,high-strength magnets,electronic equipment,etc.It is very urgent and necessary to recycle rare metals from solid wastes containing strategic resources,for example,from waste products and consumer goods with very high rare earths concentration to very low nuclear liquid wastes,industrial waste residues and waste water.In terms of liquid waste with high content of rare earth,ion exchange method,extraction method,and traditional adsorbent adsorption method can be used to recover rare earths.Among the existing methods,adsorption method is widely concerned because of its simplicity,high efficiency and low cost.In the case of the wastewater with very low concentration of rare earth ions,nano materials as adsorbents also have potential high adsorption efficiency,which is a promising technology.With regard to the perspective of resource recovery,many people have studied the effective adsorption of trivalent rare earth ions in aqueous solution by various synthetic,functionalized and characterized nano materials,and their impact on the environment and human health.In this paper,Fe₃O₄@SiO₂-NH₂,Fe₃O₄@SiO₂-COOH and magnetic tripod ligands were used as research objects to study their preparation,characterization,and adsorption effects on rare earth lanthanum,dysprosium and gadolinium ions.The characteristics of the three materials were that they could be attracted by permanent magnet,reached nanometer size,had large specific surface area,and had certain acid resistance.These characteristics were conducive to their collection in the process of adsorption of rare earth ions,could improve the adsorption efficiency due to many more active sites,and helped them possess corrosion resistance.Therefore,Fe₃O₄@SiO₂ was prepared through wrapping SiO₂ on Fe₃O₄ surface by improved St?ber method.Then the materials were prepared with amination,carboxylation,and grafting tripod ligands on the outside.Firstly,the three kinds of adsorption materials were characterized by XRD,FT-IR,and TEM combined with EDS.The phase,functional group,morphology,and element content of the materials were obtained.Secondly,the single factor test method and response surface method were used to design and optimize the experiment.The optimal adsorption conditions were selected and ensured.Thirdly,the adsorption thermodynamics and kinetics were discussed.Finally,the effect of regenerated adsorbent on the adsorption of rare earth ions was investigated.The main conclusions were as follows:1.Three kinds of magnetic nano adsorption materials Fe₃O₄@SiO₂-NH₂,Fe₃O₄@SiO₂-COOH,and magnetic tripod ligand were successfully prepared from characterizations of XRD,FT-IR and TEM.2.The highest removal rate of La???was 53.7% by Fe₃O₄@SiO₂-NH₂,at 20mg/L of initial concentration for La???,6 of p H value,and 120 min of adsorption time.The maximum adsorption capacity was 21.52 mg/g under the same conditions.The maximum removal rate of Dy???could reach 66.06% by Fe₃O₄@SiO₂-COOH,at 5 mg/L of initial concentration for Dy???,120 min of reaction time,and 7 of p H value.In the response surface method model based on single factor experiment,the removal rate of La???by magnetic tripod ligand was 99.42%,at 0.8g/L of dosage,100 min of adsorption time,and 5 of p H value.Bur the confirmatory experimental result showed that the removal rate of La???was 97.9% by magnetic tripod ligands under the same conditions.3.The adsorption process of La???by Fe₃O₄@SiO₂-NH₂ conformed to Langmuir adsorption model and pseudo second order kinetic adsorption model.It's adsorption process belonged to single molecular layer chemical adsorption.The adsorption of Dy???by Fe₃O₄@SiO₂-COOH could be described by Langmuir model and pseudo second order kinetic model.It's adsorption reaction belonged to single molecular layer chemical adsorption.The adsorption of La???by magnetic tripod ligand conformed to Freundlich adsorption and the pseudo second order kinetic model.It's adsorption process was a heterogeneous chemical adsorption on the surface.4.After 5 regeneration experiments,the removal efficiency of lanthanum ion was 40.33% by Fe₃O₄@SiO₂-NH₂.The removal efficiency of dysprosium ion is 41.58% by Fe₃O₄@SiO₂-COOH after 5 times.The removal efficiency of lanthanum ion was still 78% by magnetic tripod ligand after 5 times.