Synthesis Of Core/shell Structural Magnetic Materials And Their Adsorption Properties Of Uranium

With the continuous development of society and economy,the human demand for energy is growing.The traditional oil,coal and other non-renewable fossil fuels are gradually consumed.Today's world faces an unprecedented energy crisis.Human is seeking new sustainable energy.Nuclear energy as an economical and clean energy for sustainable development has become one of the alternatives to ease the energy shortage of world.However,mining and processing of uranium mineral resources bring a large amount of uranium pollution.Uranium is one of the most dangerous heavy metals in the environment due to the long half-life,high radioactivity and biological toxicity.Thus,the removal,recovery,and purification of uranium are of special importance.This thesis dealed with Fe₃O₄ as core and prepared a series of magnetic materials with adsorption properties,such as Fe₃O₄@SiO2@Ni-L,Fe₃O₄@TiO2,Fe₃O₄@C,Fe₃O₄@C@Ni-Al LDH and magnetic citrate Mg-Al LDH,The adsorption properties of uranium by as-prepared products are investigated.By using Fe₃O₄ as core,the obtained core/shell structure is composed of a superparamagnetic core with a strong response to external fields,which could be recovered readily from aqueous solution by magnetic separation method.The saturation magnetization of Fe₃O₄@SiO2@Ni-L is 20.9 emu/g.The composite possess high specific surface area of 382 m2/g.The results show that the Fe₃O₄@SiO2@Ni-L has excellent adsorption ability of uranium,when pH value is equal to 5.0,the maximum adsorption capacity of Fe₃O₄@SiO2@Ni-L is 129.26 mg/g.The experimental data are fitted well by pseudo-second-order equation and Langmuir model.The products characterized by SEM,TEM and VSM illustrated that as-prepared Fe₃O₄@TiO2 have a sphere morphology with a mean diameter of 200 nm and the TiO2 layer is about 50 nm in thickness.The saturation magnetization of Fe₃O₄@TiO2 is 36.0 emu/g.The isotherms of Fe₃O₄@TiO2 for uranyl ions are fitted well by Langmuir equation.The sorption follows pseudo-second-order kinetics.We prepared Fe₃O₄@C by a simple hydrothermal reaction and investigated its uranium adsorption performance.The product characterized by XRD,TEM and VSM illustrated that Fe₃O₄ have a quasi-spherical shape with a mean diameter of 10 nm and the carbon layer is about 10 nn in thickness.The saturation magnetization of Fe₃O₄@C is 8.25 emu/g.The maximum adsorption capacity of uranium by Fe₃O₄@C is observed at pH = 6.0.The adsorption of uranium?VI?reaches equilibrium after 360 min and follows pseudo-second-order kinetics.The use of in situ growth method allows LDH nanosheets to become strongly and uniformly anchored onto the surface of Fe₃O₄@C.This work prepared a high efficient magnetic composite adsorbent with high adsorption capacity.The saturation magnetization of Fe₃O₄@C@Ni-Al LDH is 2.20 emu/g.The uranium adsorption capacity increases steeply with the increase of pH value,and reahes a maximum when the pH value is 6.0.After that,the adsorption capacity decreased.The experimental data are fitted well by a pseudo-second-order equation and Langmuir model.Magnetic citrate Mg-Al LDH,which had C6H5O73-intercalated in the interlayer,was prepared via ion-exchange technique.For magnetic citrate.Mg-Al LDH,intercalation of the chelating agents in CO3 Mg-Al LDH increased d003 from 7.7 A to 11.6 A,the broadened XRD peaks corresponding to the basal spacing are located at lower 26 values than those of CO3·Mg-Al LDH,also indicative of a larger interlayer spacing.The saturation magnetization of magnetic citrate·Mg-Al LDH is 7,73 emu/g.Due to the introduction of citrate ions,the adsorption ability of magnetic citrate·Mg-Al LDH particles for uranyl ions is higher than magnetic Mg-Al LDH.The maximum adsorption capacity of uranium by magnetic citrate·Mg-Al LDH is observed at pH 6.0.The sorption follows pseudo-second-order kinetics.