Study On Adsorption Of U(Ⅵ) By Amidoxime Acrylonitrile-imidazole Copolymer

With the development of nuclear energy,the demand for uranium is also increasing.The reserves of uranium resources on land are limited and the mining will lead to a series of environmental pollution problems.Therefore,it is particularly important to extract uranium from seawater.The adsorption materials with amidoxime are currently the most widely studied.However,only oxime based adsorption materials are not the best one for the extraction of uranium from seawater.Therefore,we first synthesized the amidoxime acrylonitrile-ethylimidazole copolymer[P（AO/C₂VIM⁺Br^-）]adsorption material which contained imidazole cations by grafting imidazole cations to amidoxime polymerized adsorption materials.And then,the amidoxime acrylonitrile-hexylimidazole copolymer[P（AO/C₆VIM⁺Cl^-）]and the amidoxime acrylonitrile-dodecylimidazole copolymer[P(AO/C₁₂VIM⁺Cl^-)]were synthesized by changing the length of the substituent carbon chain in the imidazole cation.Finally,the synthesized materials were characterized by Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,nuclear magnetic resonance proton spectroscopy（¹H-NMR）,and elemental analysis.The adsorption behavior of uranium on P（AO/C₂VIM⁺Br^-）,P（AO/C₆VIM⁺Cl^-）and P(AO/C₁₂VIM⁺Cl^-)was studied by static batch adsorption experiments.The effects of solid-liquid ratio,adsorption time,pH,ionic strength,coexisting ions and temperature on the adsorption of uranium were carried out.Meanwhile,the adsorption thermodynamics and kinetics of uranium on synthetic materials were studied.The mechanism of P（AO/C₂VIM⁺Br^-）,P（AO/C₆VIM⁺Cl^-）and P(AO/C₁₂VIM⁺Cl^-)adsorption of uranium was inferred from the adsorption kinetics and thermodynamics models,combined with FTIR and XPS.The experimental results showed that the adsorption percent of U（Ⅵ）on materials increased with the increasing of the solid-liquid ratio.The equilibrium time for U（Ⅵ）adsorption on P（AO/C₂VIM⁺Br^-）was the shortest,which showed a fast adsorption process.The ionic strength has no significant effect on the adsorption of U（Ⅵ）by these materials.The increaseing temperature can promote the adsorption capacity of U（Ⅵ）on P（AO/C₂VIM⁺Br^-）,P（AO/C₆VIM⁺Cl^-）,and P(AO/C₁₂VIM⁺Cl^-).The adsorption processes were all endothermic reactions.The U（Ⅵ）adsorption process of these materials conformed to the pseudo-second-order kinetic model and the monolayer adsorption model by studying adsorption kinetics and adsorption thermodynamics.The maximum adsorption capacity of U（Ⅵ）on P（AO/C₂VIM⁺Br^-）is 69.83 mg/g U under pH 8.0 or so.we found that the adsorption of uranium on these materials can still be maintained above 60%by simulation seawater experiments,which indicated that it was a good adsorbent for uranium.By the desorption experiment,it was found that the mixed solution of 0.1 mol/L Na₂CO₃ and 0.1 mol/L H₂O₂ was the best desorption agent for U（Ⅵ）,and the adsorption performance is basically unchanged after three times of reuse.