Study On The Synthesis Of Ternary Hydrotalcite And The Separation Of Simulated Radionuclide Uranium

With the rapid development and application of nuclear energy,nuclear energy not only benefits human beings,but also releases a large number of radionuclides into the environment,which poses a great threat to the ecological environment and human health.Hydrotalcite is a kind of anionic clay mineral material with positive surface charge and layered structure.In recent years,due to its unique layered structure,"memory effect"and interlayer anion exchange performance,it has attracted much attention in the field of pollution remediation.In this paper,the separation and removal of radionuclide uranium in uranium-containing wastewater is taken as the research objective,and the treatment effect of ternary hydrotalcite prepared by different methods on uranium-containing wastewater were studied.Through batch experiments,the influences of time,temperature,material dosage and other factors on the uranium removal effect of ternary hydrotalcite separation were discussed.The main conclusions are as follows:（1）Using urea,NiCl₂·6H₂O,ZnCl₂,CaCl₂·2H₂O,MgCl₂·6H₂O,AlCl₃·6H₂O and FeCl₃·6H₂O as raw materials,a variety of hydrotalcites have been successfully prepared by hydrothermal synthesis to adsorb U（Ⅵ）in uranium-containing wastewater.The adsorption experiment results showed that the adsorption capacity of ternary hydrotalcite was higher than that of binary hydrotalcite,and the influence degree of cations on uranium adsorption efficiency was Ni²⁺>Zn²⁺>Fe³⁺～Al³⁺>Ca²⁺>Mg²⁺.（2）The porous honeycomb ZnNiFe-LDH was successfully prepared to treat 10 mg/L uranium-containing wastewater.The results of static adsorption experiments showed that the adsorption rate of ZnNiFe-LDH on U（Ⅵ）was 97.57%when the dosage of ZnNiFe-LDH was 0.1 g/L,the pH was 5,the reaction time was 120 min and the initial concentration of uranium was 10 mg/L.The adsorption kinetics and thermodynamic experiments showed that ZnNiFe-LDH adsorption of uranium was a spontaneous endothermic reaction,and the quasi-second-order kinetics model and Langmuir isothermal adsorption model could better describe the adsorption process of uranium by ZnNiFe-LDH.Combined with SEM-EDS,FI-IR,XPS and XRD,it was found that the main mechanism of ZnNiFe-LDH LDH on uranium was surface complexation.At T=25℃,the saturated adsorption capacity of ZnNiFe-LDH for uranium fitted by Langmuir isothermal adsorption model for uranium was 689.66 mg/g,and the adsorption capacity for uranium of Z_0.67N_1.33F₁-8 prepared by orthogonal experiment was 980.77 mg/g.The adsorption capacity of other zinc-nickel-iron ternary hydrotalcites for uranium was also above400 mg/g,indicating that the zinc-nickel-iron series hydrotalcite had great potential in the treatment of uranium-containing wastewater.（3）Using Na₂CO₃ as alkali solution for real-time synthesis of CaMgFe-LDH to treat high-concentration uranium-containing wastewater,orthogonal experiment confirmed that the optimal experimental scheme of real-time synthesis of CaMgFe-LDH was n M²⁺:n M³⁺=4:1,n M³⁺:n Na₂CO₃=2:5,n Ca²⁺:n Mg²⁺=1:1,and the reaction time was 120min.Under the optimum scheme,CaMgFe-LDH was synthesized in real time to treat 100 mg/L simulated uranium-containing wastewater.and the removal rate of uranium was 95.63%.It indicated that the real-time synthesis of CaMgFe-LDH for the treatment of high-concentration uranium containing wastewater had a great application prospect,which provided a good research basis for calcination of hydrotalcite into spinel to solidify uranium.（4）Using Na₂CO₃/NaOH as lye to synthesize CaMgFe-LDH treat low-concentration uranium-containing wastewater in real time.Single factor experiments showed that:real-time synthesis of CaMgFe-LDH had a good effect on treating low-concentration of 10 mg/L U,and the ratio of metal cations to anions in the system was the key to highly efficient removal of uranium by hydrotalcite.According to the general structure formula of hydrotalcite[M²⁺_1-xM_x³⁺（OH）₂][A^n-]_x/n·m H₂O,the removal rate of 10 mg/L uranium containing wastewater by real-time synthesis of CaMgFe-LDH was more than 99%,which could treat low concentration uranium containing wastewater below 0.3 mg/L,and had great application prospects in the in-situ treatment of uranium-containing wastewater.