The Preparation And Adsorption Properties Research Of Modified Fe₃O₄ Magnetic Adsorption Materials And Molecularly Imprinted Adsorbent Materials

Magnetic nanocomposites have widely applied in catalysis,ferrofluid,bio-medicine,biochemical separation because of their special structures and properties.Especially,the magnetic nanocomposites based on Fe₃O₄ nanoparticles,can be effectively separation and recovery under external magnetic field due to their superparamagnetism,other than the conventional magnetic materials.Heavy metal ions are hard to transfer in the environment and could enter waters through various channels.After enrichment through various biological chains in waters,then eventually accumulated in human bodies and caused various diseases.Therefore,the studies on removal of heavy metals from waters have inspired much interest among researchers.Core-shell structure magnetic adsorption materials are regarded as one kind of very important magnetic nanocomposites,have shown great potential for removing heavy metal ions.Though Fe₃O₄ magnetic nanoparticle is widely used in many fields because of its magnetism and super small size,the uncoated magnetic nanoparticles in themselves have some limitations,such as easily agglomerate and absence of dispersibility.After coated with silica,polymers or other coating materials on the surfaces of Fe₃O₄ could help prevent their aggregation in liquid and improve their chemical stability.The surface of silica coated magnetic nanoparticles is often terminated with silanol groups that can be further functionalized and react with various coupling agents to covalently attach specific ligands to the surfaces of these magnetic nanoparticles.Such a capability will open the door to the design and synthesis of magnetic carrier materials that can be used to biochemical analysis with intensified performance.The main researches of this dissertation are as follows:?1?Preparation of modified Fe₃O₄ magnetic adsorption materials,and studied the factors that influence the adsorption capacity of magnetic materials on copper ions;?2?Preparation of Simazine molecularly imprinted polymers and Morin molecularly imprinted polymers respectively,and studied the adsorption capacity of the two molecularly imprinted adsorbent materials on their respective template molecules.The specific research contents are as follows:1.In the second chapter,the heavy metal ions pollution and damages have been reviewed.The separation and enrichment methods of heavy metals are systematically introduced.Then,the properties and preparation methods of superparamagnetic iron oxide nanoparticles are introduced briefly.The approach of coating silicon on the surface of superparamagnetic iron oxide nanoparticles are illustrated.2.In the third chapter,a magnetic composite material with excellent properties was synthesized with particulate magnetic Fe₃O₄ nanoparticles as core materials,silica with a high specific surface area was used as shell materials and carboxyl groups were used for the end-capping modification and research the adsorption capacity for copper ion.During the preparation of the material,the magnetic Fe₃O₄ nanoparticles were prepared by coprecipitation method firstly,then generated silica coatings on the surfaces of ferriferrous oxide particles relied on the well-known St?ber process,in which silica was formed in situ through the hydrolysis and condensation of a sol-gel precursor,followed with after that the Fe₃O₄@SiO₂ core-shell composite materials was obtained.Afterwards,introduced the stable covalent immobilization of the trimethoxysilylpropanethiol on the surface of Fe₃O₄@SiO₂ system by a click chemistry approach obtained Fe₃O₄@SiO₂@SH.Then AIBN was used as initiator to graft polymerization of 2,2'-??4-vinylbenzyl?imino?diacetic acid on the surface of Fe₃O₄@SiO₂@SH to prepare carboxyl end-capped magnetic adsorbent Fe₃O₄@SiO₂@SH@VBIDA.The physical structure of this materials in ferriferrous oxide series were identified using X-ray diffractometer,vibrating sample magnetometer,Fourier transform infrared spectroscopy,thermogravimetric analysis,transmission electron microscopy and zeta potentiometer.The results show that the prepared spherical ferriferrous oxide particles have a particle size of about 20 nm and the saturation magnetization is 68.21 emu/g.The thickness of the silica coating layer is about 20 nm with a saturation magnetization about 17.24 emu/g.The adsorption of Fe₃O₄@SiO₂@SH@VBIDA for copper ions in aqueous solution was studied.The effect factors on adsorption performance of the materials was investigated,including the dosage of adsorbent,the p H of the adsorption solution,ionic strength and test temperature.The results indicate that the adsorption performance of the materials are significantly affected by p H and the dosage,the adsorption performance varies with p H and the dosage.The ionic strength of the adsorption solution has a few effect on the adsorption performance of the material.The isothermal adsorption,kinetic adsorption,thermodynamic adsorption and adsorption mechanism of magnetic materials were discussed.The adsorption equilibrium time of Fe₃O₄@SiO₂@SH@VBIDA for copper ion in aqueous solution is about 30 mins,the adsorption process followed the pseudo-second order model.The thermodynamic adsorption results showed that the adsorption isotherm data for copper ion was consistently with Langmuir isotherm.The maximum adsorption capacities at 293.15 K,303.15 K,and 313.15 K are 221.24 ?g/g,264.55 ?g/g,and 292.40 ?g/g,respectively.The copper ion loaded magnetic adsorption materials mixed with HCl solution about 6 hours reached desorption equilibrium at room temperature and revealed good recycling ability.The method of preparing the magnetic adsorption materials have many advantages,such as simple chemical synthesis process,low cost,and mild reaction conditions.Under the action of an external magnetic field,the magnetic materials can realize solid-liquid separation rapidly thus improved the experimental efficiency effectively,and at the same time,it is easy to recycle the materials.The materials have good application on the studies of adsorption and removal of copper ions.3.In the fourth chapter,two different molecularly imprinted polymers were prepared by using triazines simazine and flavonoids morin as the template molecule respectively.The influences of the types of monomers,solvents and the ratios between template molecule,monomer,cross-linking agent on the adsorption efficiency of the prepared imprinted polymers are discussed.