Preparation Of Dendritic Magnetic Fe₃O₄ Nanocomposites And Their Adsorption Of Heavy Metal Ions

In this paper,a series of dendritic magnetic nanocomposites(Fe3O4@SiO2-TMT-SH,Fe3O4@SiO2-PAMAM-Crown and Fe3O4@SiO2-PAMAM-NTA)were prepared using chlorine-based and amino functionalized magnetic Fe3O4@SiO2 as pre-carriers.Used to adsorb heavy metal ions Pb2+,Cd2+,Ni2+in water.And explore the influence of various factors on the adsorption performance(pH,temperature,initial concentration and ionic competition,etc.),the dendritic magnetic nanocomposites were studied the possible mechanism of the adsorption of recycling performance and the main research content is as follows:(1)Chlorine-functionalized magnetic Fe3O4@SiO2 was used as the front carrier to modify its surface,and 1,3,5-phenyltrithiophenol was inserted on its surface to form dendritic magnetic nanocomposite Fe3O4@SiO2-TMT-SH,which was used to adsorb Pb2+heavy metal ions in aqueous solution.The results show that the optimal pH is 6.5,and the time required for the adsorption process to reach the adsorption equilibrium is 15min.The adsorption data of Pb2+ on the adsorbent fit the Frenudlich isotherm model and the pseudo-second-order kinetic model.When the initial concentration of heavy metal ions is 250 mg/L and the optimal conditions are met,the maximum adsorption capacity of Fe3O4@SiO2-TMT-SH for Pb2+is 236.45 mg/g.At the same time,Fe3O4@SiO2-TMT-SH was characterized by SEM,TEM,XRD,VSM,XPS and FTIR to study the appearance and surface properties of magnetic composites.Through VSM characterization of magnetic composite Fe3O4@SiO2-TMT-SH,it is found that it has superparamagnetic properties,and the saturation magnetic strength is 60.1emu/g.After several adsorption and analytical experiments,the adsorption efficiency of Fe3O4@SiO2-TMT-SH for Pb2+ can still reach more than 95%.In addition,we also carried out the adsorption mechanism analysis,and found that the magnetic nanocomposite Fe3O4@SiO2-TMT-SH has a strong chelating effect on the heavy metal ion Pb2+.(2)The dendritic magnetic composite Fe3O4@SiO2-PAMAM was prepared under mild conditions,and further grafting treatment was carried out on the basis of which the dendritic surface was covered with a large number of carboxyl functional groups,and finally the dendritic magnetic nanocomposite Fe3O4@SiO2-PAMAM-NTA was synthesized.Due to the coarser surface of Fe3O4@SiO2-PAMAM-NTA and larger specific surface area,the surface target functional groups of magnetic nanocomposites are more dense and abundant.In this paper,the magnetic composite Fe3O4@SiO2-PAMAM-NTA was synthesized to adsorb Cd2+,and the magnetic composite was characterized by SEM,TEM,XRD,VSM,XPS and FTIR.The appearance and surface properties of the magnetic composite were studied.By characterizing Fe3O4@SiO2-PAMAM-NTA,it presents superparamagnetic with a saturation magnetic intensity of 48.5emu/g.After five cycles of experiments,the adsorption efficiency of Fe3O4@SiO2-PAMAM-NTA for Cd2+ can still reach above 96%.Through experimental design and experimental data analysis,the adsorption of Fe3O4@SiO2-PAMAM-NTA on Cd2+is a kind of electrostatic force adsorption.(3)Synthesis of dendritic core-shell structure of magnetic nanocomposites Fe3O4@SiO2-PAMAM,the modification is introduced into 18-crown-6,15-crown-5,12-crown-4 crown ether,etc.Thus the magnetic composite with dendritic structure Fe3O4@SiO2-PAMAM-Crown was prepared.The applications of crown ethers in magnetic coincidence materials are discussed from three aspects.The first is the selectivity of the inner diameter of crown ether material for the adsorption of heavy metal ions,because the inner diameter of crown ether and the size of heavy metal ions will determine the strength of the chelating force in the inner cavity of crown ether.The second is the influence of heteroelements on crown ether adsorption of heavy metal ions.Crown ethers take C and O elements as the skeleton,thus forming a ring structure.Therefore,when the oxygen element is replaced by other elements,it will directly affect the adsorption of crown ethers to heavy metal ions.This is because oxygen plays a leading role in the chelation of heavy metal ions by crown ethers.Finally,compared with other magnetic composites modified by crown ether,different synthesis methods are adopted in this paper.After the introduction of magnetic composite materials,the crown ether adsorption of heavy metal ions will be recycled.