Preparation Of Magnetic Fe₃O₄ Nanocomposites And Its Study On Adsorption Of Methylene Blue In Aqueous Solution

In this paper,three organic functionalized Fe3O4@SiO2 magnetic nanocomposites were prepared and used to adsorb methylene blue(MB)in aqueous solution.The samples were characterized by high-resolution transmission electron microscopy(HR-TEM),scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),vibrating sample magnetometer(VSM)and thermogravimetric-differential scanning calorimetry(TG-DSC).Kinetic studies show that the adsorption of MB on these magnetic nanoparticles is in accordance with pseudo-second-order kinetics,and the isotherm studies show that the adsorption of MB on these magnetic nanoparticles is consistent with Frenudlich isotherm model.In addition,the paper also explored the regeneration performance of three magnetic composites and the mechanism of the related adsorption process.The main research contents are as follows:(1)Congo red functionalized Fe3O4@SiO2 magnetic nanocomposites(Fe3O4@SiO2-CR)were prepared for the adsorption of MB in aqueous solution.The magnetic properties study shows that Fe3O4@SiO2-CR magnetic nanoparticles without remanence and coercivity,and have high saturation magnetization(55.8 emu/g).In addition,the results show that adsorption is favorable high pH value,and the adsorption equilibrium time is 10 minutes.The maximum adsorption capacity of MB on Fe3O4@SiO2-CR nanocomposites at room temperature was 31.44 mg/g.After four cycles of experiments,the removal rate of MB by Fe3O4@SiO2-CR nanocomposites is still higher than 55%,indicating that the regeneration performance of magnetic nanomaterials is good.In addition,we also discussed the possible adsorption mechanism,and the results show that the main adsorption mechanism is electrostatic interaction.(2)The magnetic Fe3O4@SiO2 particles functionalized by ethylenediamine(Fe3O4@SiO2-EDA)were used as reactants,and maleic acid was grafted on the surface to prepare dendritic carboxylic functionalized Fe3O4@SiO2 nanocomposites(Fe3O4@SiO2-EDA-COOH).The saturation magnetic strength is 58.7 emu/g,which is beneficial to fast magnetic separation.TG analysis showed that the magnetic nanoparticles have good thermal stability and no significant thermal decomposition at 800℃.The maximum adsorption capacity of MB for Fe3O4@SiO2-EDA-COOH nanocomposites was 43.15 mg/g at room temperature.After five cycles of experiments,the removal rate of MB by Fe3O4@SiO2-EDA-COOH is still 68%,indicating that the magnetic nanomaterial has good regeneration performance.In addition,we also discussed the possible adsorption mechanism,and the results show that the main adsorption mechanism is electrostatic interaction.(3)5-Aminoisophthalic acid functionalized magnetic nanocomposites(Fe3O4@SiO2-APTA)were prepared by using chloropropyl functionalized Fe3O4@SiO2 magnetic nanomaterials(Fe3O4@SiO2-Cl)as reactants,and their saturation magnetic strength is 45.8 emu/g,which is beneficial to magnetic separation.The maximum adsorption capacity of MB for Fe3O4@SiO2-APTA nanocomposites was 46.24 mg/g at room temperature.After five cycles of experiments,the removal rate of MB by Fe3O4@SiO2-APTA nanocomposites is still 70%,indicating that Fe3O4@SiO2-APTA nanocomposites have good regeneration performance.In addition,adsorption mechanism studies have shown that the main adsorption mechanism is electrostatic interaction.