| Uranium is a necessity for national defense construction and nuclear power,but the amount of uranium stored on land can only sufficient for human using for 100 years.There are 450 million tons of uranium in the sea,can meet the human’s needs for uranium resources in the future.Magnetic nanomaterials are widely used in the preparation of adsorbents because of their small volume,large specific surface area,easy separation under an external magnetic field,possessing specific surface active sites and the sites can be easily chemically modified and functionalized.Adsorption of uranium ions in solution by magnetic nanomaterials has attracted the attention of many scientists.In this experiment,a novel magnetic core-shell CoFe2O4@SiO2@PIL-AO adsorbent was synthesized and then characterized by scanning electron microscopy,infrared spectroscopy and X-ray photoelectron spectroscopy,and its adsorption performance on uranium ions in water and simulated seawater was studied.The influence of pH value,initial concentration of uranium solution,reaction time,temperature and coexisting ions on uranium adsorption in water were studied by single-factor experiment to obtain the optimum adsorption conditions,the highest adsorption efficiency and the maximum adsorption capacity.At the same time,the desorption and regeneration experiments were carried out to study the regeneration ability of the adsorbent and its economic efficiency,and the adsorption of uranium ions in simulated seawater by CoFe2O4@Si O2@PIL-AO was implemented to predict the adsorption effect of adsorbent in real seawater.The adsorption mechanism of CoFe2O4@SiO2@PIL-AO was analyzed by studying the thermodynamics,kinetics and adsorption isotherms.The SEM image shows that CoFe2O4 is a uniformly spherical particle.After coated SiO2,the diameter of spherical particles become larger and the surface becomes smoother.The size of the spherical particles further increases and adhesion phenomenon occurs between the particles after grafting PCMVImCl ionic liquid.After oximation reaction of CoFe2O4@SiO2@PIL,CoFe2O4@SiO2@PIL-AO particles are still spherical,but the adhesion phenomenon between particles is more obvious.FT-IR and XPS characterization demonstrated that the cyano group was successfully grafted onto the surface of CoFe2O4@SiO2 and could be successfully converted to amidoxime.The experimental results showed that the adsorption rate of uranium ions in aqueous solution can reach more than 90%when the pH of the solution is in the range of 5.5 to 9.0.And under the conditions of initial uranium concentration is 0.2 mg·L-1,pH=6.00±0.05,T=298.15 K,m=0.02 g,t=8 h,the maximum adsorption efficiency of this material for uranium is 97.54%.The adsorption of uranium ions by CoFe2O4@SiO2@PIL-AO conform pseudo-second-order model and Freundlich isotherm model,indicating that the adsorption process mainly belongs to multi-layer chemisorption and strong complexation.Thermodynamic studies（ΔS,ΔH andΔG）show that the adsorption process is a spontaneous and endothermic process.In addition,with hydrochloric acid(0.1 mol·L-1)as the desorption agent,the adsorption rate decreased only 0.013 mg·g-1after five times of adsorption-desorption experiments.The adsorption of uranium ions in aqueous solution illustrate that CoFe2O4@SiO2@PIL-AO has good selectivity and affinity for uranium ions.The adsorption rate of CoFe2O4@SiO2@PIL-AO to uranium ions in simulated seawater(uranium ion concentration 8.075μg·L-1)was 87.07%.In summary,the magnetic core-shell CoFe2O4@SiO2@PIL-AO material has great potential to adsorb uranium ions from seawater. |
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