Synthesis Of Functionalized Fe₃O₄Nanoparticles For Hg（Ⅱ） Ions Adsorption

Fe₃O₄has a wide range of applications in biomedical and other fields because of manysuperiorities include large specific surface area, higher saturation magnetization strength andeasy-surface-functionalization. As one of the soft magnetic materials, Fe₃O₄is not onlywidely used as catalyst, magnetic polymer microspheres, recording materials, magneticmaterials, pigment and electronic materials，but has also potentially applied in the field ofabsorption materials for pollutants elimination in recent years. The problem of environmentpollution increases along with the development of productivity and science and technology.The heavy metal pollution of water has become a global problem which is a serious threat tothe human health and lives. For the purpose of effective enrichment and separation for thetrace heavy metal ions in solution, we have synthesized two kinds of functionalized Fe₃O₄magnetic nanoparticles and applied them to adsorb the mercury （Hg（Ⅱ）） in solution. The mainresearch contents are as follows:Firstly, using Fe2+as precursors, oxygen in air as oxidant and L-cysteine （L-Cys） asprotectant, the uniform Cys-functionalized Fe₃O₄magnetic nanoparticles （Fe₃O₄-Cys NPs）was obtained by oxidation-precipitation method with the assistance of sonication. Theproperty of the NPs was characterized by Fourier transform infrared spectroscopy （FTIR）,transmission electron microscope （TEM）, X-ray diffraction （XRD）, vibrating samplemagnetometer （VSM）, thermogravimetric analysis （TGA） and dynamic light scattering （DLS）.Results showed the formation of surface chemical bonds between L-Cys and Fe₃O₄NPs andthe content of L-Cys on the surface of Fe₃O₄was²3%. The diameter of the NPs was smalland uniform （¹5nm）. In addition, these NPs expressed high magnetic responsiveness,superparamagnetism and high heat-stability.Secondly, the lipophilic thiol-functionalized Fe₃O₄magnetic nanoparticles （Fe₃O₄-EDTNPs） were obtained by multi-step synthesis. Basing on the traditional co-precipitation method,using SDS as dispersant, Fe₃O₄magnetic nanoparticles modified with SDS was successfullysynthesized. Further discussed the influence of SDS on the dispersion and magneticresponsiveness of Fe₃O₄-SDS NPs. Results showed the Fe₃O₄-SDS NPs expressed goodmagnetic responsiveness and dispersion when the mole ratio of SDS and Fe₃O₄was1:2. Thenthe experiment used EDT as functionalization reagent, with the ultrasound treatment,Fe₃O₄-EDT NPs was successfully synthesized. The property of these NPs was characterizedby Fourier transform infrared spectroscopy（FTIR）, transmission electron microscope （TEM）,energy dispersive spectroscopy（EDS）, X-ray powder diffraction（XRD）, vibrating samplemagnetometer（VSM） and thermogravimetric analysis（TGA）. Results showed the hydrophilicFe₃O₄-SDS NPs changed into lipophilic NPs after several times of water scrubbing, whichwas beneficial to the synthesis of lipophilic Fe₃O₄-EDT NPs. The existence of SDS and EDT on the Fe₃O₄-EDT NPs was confirmed by the infrared analysis results. The diameter ofsynthesized Fe₃O₄-EDT NPs was about15nm and these particles dispersed well in the systemof ethanol/water （1:1）. These NPs expressed high magnetic responsiveness when the moleratio of Fe₃O₄and EDT was1:8.Finally, the adsorption performance of these NPs for trace amount of mercury （Hg（Ⅱ）） insolution was investigated. We also discussed the influence of pH, adsorption time andabsorbent dosage on the finally adsorption efficiency. It was found that the adsorptionefficiency of Fe₃O₄-Cys NPs was95%at the optimal conditions. The adsorption rate constantbased on the formula of Lagergrent was0.22min-1, indicating the Hg（Ⅱ） in water can beadsorbed rapidly by the Fe₃O₄-Cys NPs. In addition, it was found that low dose of Fe₃O₄-EDTNPs can be used to efficiently adsorb mercury （Hg（Ⅱ））（85%） in a short time （5min）. Fromthe experimental results, the adsorption efficiency of trace Hg（Ⅱ） in solution was different.That is because of the different surface property of nanoparticle. At last, both of thesefunctionalized Fe₃O₄magnetic nanoparticles achieved the satisfactory adsorption effect. Inthis paper, the research result has certain significance on the treatment and remove of heavymetal ions in industrial waste water and daily drinking water.