Preparation And Properties Of Iron-based On Simulated Seawater Uranium Adsorption Materials

Nuclear power is considered as a safe,clean and sustainable new energy.The sustainable development of nuclear energy depends on continuous supply of nuclear fuel,which used in nuclear reactions comes from uranium mine in land.China belongs to the depleted uranium country and the land is lack of uranium mine.Researches proved uranium reserves in China can only maintain the existing nuclear power installed capacity for 30 years.Nuclear fuel resource will depend on import in the future.The abundant uranium source in seawater has attracted increasing attention,because it is about thousand times as those in land.It is important to exploit uranium from marine environments to provide enough fuel for nuclear power and relieve the energy crisis.By taken into consideration of low concentration uranium in seawater,magnetic organic functional composite adsorbents based on Fe₃O₄ and CoFe₂O₄were synthesized.Effects of pH,initial uranium concentration and contact time on adsorption were investigated.The thermodynamics and dynamics behaviors between uranium and magnetic adsorbents in the adsorption process were studied by fitting the thermodynamic and dynamic models.Simulated seawater adsorption experiment and ions competition adsorption experiment were carried out at the same time.Carbon coated iron oxide?Fe₃O₄@C?was synthesized by one-step solvothermal reaction.Ketoxime-functionalized carbon coated iron oxide?Fe₃O₄@C–KO?was fabricated through surface functionalization of Fe₃O₄@C with ketoxime.The saturation magnetization of the composites is 30.33 emu/g,showing good magnetic response and dispersion in solution.The adsorption process was completed in 60 minutes when the optimum pH was 6.0.The adsorption experiment data revealed that the process followed pseudo-second-order kinetic model and the adsorption of uranium?VI?was well-described by the Langmuir isotherm.Thermodynamic parameters further showed that the sorption was an endothermic and spontaneous process.Comparing with Fe₃O₄@C,Fe₃O₄@C–KO is a powerful and promising sorbent for the efficient extraction of uranium?VI?because of the chelation between uranyl ion and-OH in ketoxime.The amino-functionalized magnetic Fe₃O₄ nanoparticles?Fe₃O₄-APTMS?were prepared via encapsulation of Fe₃O₄ nanoparticles with?3-aminopropyl?trimethoxysilane.The adsorption results showed the optimum pH value was 6.0 and optimum contact time was 60min.The saturated adsorption capacity of uranium by Fe₃O₄-APTMS was 160.8 mg/g at 25^oC.In addition,the adsorption-desorption experiment in NaOH solution showed that Fe₃O₄-APTMS exhibited high regeneration and reusability.The adsorption of uranium?VI?is well-described by the Langmuir isotherm and the adsorption process is spontaneous endothermic.The surface modified Fe₃O₄@SiO₂ magnetic materials with a core-shell structure were prepared.Fe₃O₄@SiO₂-PEI magnetic particles form a spherical shape with a diameter of about 260-300 nm.The saturation magnetization of the composite materials was 56.76 emu/g.The equilibrium adsorption capacity was 278.16 mg/g at optimum pH 7.0 after 240 min.The adsorption process was best described by a pseudo-second-order kinetic model.The uranium sorption equilibrium data fitted well with the Langmuir sorption isotherm model.Simulated seawater adsorption experiments showed that the removal rates were more than 90%when the concentration of uranium was less than 30?g/L,proving that Fe₃O₄@SiO₂-PEI remained good adsorption performance.Ions competition adsorption experiment showed those adsorbents had the high selectivity for uranium ions in the presence of many competitive cations.Cobalt ferrite/multiwalled carbon nanotubes?CoFe₂O₄@MWCNTs?with magnetic responsiveness performance were successfully synthesized by a hydrothermal method,Polypyrrole/Cobalt ferrite/multiwalled carbon nanotubes adsorbents were obtained after surface modification with Polypyrrole.Batch adsorption experiments revealed that the optimum pH of CoFe₂O₄@MWCNTs-PPy was 7.0,which was close to pH value of seawater.When the pH is 8.0,CoFe₂O₄@MWCNTs-PPy still had high adsorption capacity of 104 mg/g,so CoFe₂O₄@MWCNTs-PPy will be more suitable for the extraction of uranium from the seawater.0.5 mol/L NaHCO₃ was the best desorbent for both two adsorbents.The magnetic composite adsorbents still shown good adsorption properties with adsorption capacity of 100mg/g after the three times adsorption–desorption procedures.