Design And Fabrication Of Magnetic Core-shell Composites

Multifunctional materials with task-specific physicochemical properties, especially core-shell nanostructures with Fe3O4core and NH2-functional shells (Fe3O4@SiO2-NH2), have become one research focus of many areas. Due to the special magnetic properties, high surface area, low cost, non-toxicity and biocompatibility, the magnetic multifunctional materials have gained their much attention in many field, for example, the separation of protein or DNA, targeted drug delivery in biomedicine applications; the detector and separation of heavy metal in environmental application and catalysis fields. In this thesis, we introduced the synthesis, characterization and performance of Fe3O4@SiO2-NH2core-shell nanomaterials.Herein, firstly the magnetic Fe3O4MNPs were prepared through the solvothermal method; and then we demonstrated that mono-dispersed and spherical Fe3O4@SiO2-NH2core-shell nanomaterials with magnetic response core, relatively high loading of amino functionality NH2-functional shell structure can be facilely prepared by co-condensation of TEOS with APTMS using an versatile sol-gel process. It was shown that the proper usage of APTMS and appropriate pre-hydrolysis time of TEOS were crucial and key steps for the formation of highly uniform and desirable amino loading Fe3O4@SiO2-NH2materials. The TEOS pre-hydrolysis and the critical time before the addition of APTMS prove to be vital for uniform structure evolution, while the appropriate concentration of APTMS leads to well-dispersed materials with relatively high loading of amino functionality. Furthermore, the effects of different content of amino group on the formation of MNPs and the structural properties of as-prepared nanomaterials were studied in details.Secondly, the as-prepared Fe3O4@SiO2-NH2MNPs were employed in adsorption of Pb(Ⅱ) ions from aqueous systems and the maximum Pb(Ⅱ) adsorption occurred in the range of pH5-6with maximum adsorption capacity of238mg/g at25℃. The adsorption isotherm fitted the Langmuir model well and the kinetic adsorption indicated that the pseudo-second-order rate equation characterized the kinetic curves better than the pseudo-firs- -t-order rate equation. The ther-modynamic data suggested that the adsorption of Pb(Ⅱ) onto Fe3O4@SiO2-NH2MNPs was a physisorption process. Moreover, Fe3O4@SiO2-NH2MNPs adsorbents can be regenerated easily and used repeatedly for many cycles. On the basis of observed experimental data, the acceptable adsorption capacity of the synthesized Fe3O4@SiO2-NH2MNPs and the fascinating magnetic separability features of the adsorbent endow them with a more efficient and convenient separation method so that the time-consuming solid-phase separation procedure can be favorably avoided and hence can be considered as a potential material for Pb(II) removal for wastewater treatment process.