The Migration Of Radionuclide During The Smelting Of Rare Earth And Study On Adsorption Of Radionuclides By MOFs Materials

Rare earth smelting separation process would produce a large number of radioactive tailing,the waste must be properly disposed of to avoid causing radioactive contamination of the environment.In this paper,starting from the process of rare earth smelting,this paper analyzed the transfer of natural radionuclides thorium,uranium and radium in rare earth smelting process,and calculated the activity of radioactive tailing and the content of radionuclides of uranium,thorium and radium.At the same time,the removal of radioactive waste water and tailing residue were studied.The adsorption of radioactive waste water containing cesium ions by MOF-76（Sm）was also studied.It provided a theoretical basis for the extraction of useful nuclides in rare earth tailing and reuse of tailing residue.The main contents and conclusions are as follows:（1）Using X-fluorescence to analysis the tailing and Inductively coupled plasma mass spectrometry（ICP）to analysis the water which come from the process of smelting.Those results reflected that the Th and Ra that came from tailing were concentrated in acid-soluble tailing,but U was concentrated in neutralization tailing.Moreover,we found that the radioactive of acid-soluble tailing was higher than neutralization tailing.By analyzing the process of smelting and results of FITR,XRD,we found that the contents of acid-soluble tailing were Ba（SO₄）;SiO₂;insoluble species and sodium of rare earth;the mainly forms of Th and Ra in acid-soluble tailing were Th0₂;Th₃（PO₄）₄;RaSO₄,respectively.The contents of neutralization tailing were:CaC₂O₄;NaCl;carbonate and oxalate of rare earth,the mainly forms of U in neutralization tailing were U（OH）₄ and diuranate,respectively.At the same time,the removal of the extraction wastewater was studied.When pH was 8.1 and the addition of BaCl₂ was 0.33g/L,the removal efficiency was better.（2）The radioactive tailing was measured and analyzed using gamma spectrometer,the natural radioactive balance of rare earth tailing has been destroyed.In the case of equilibrium destruction,the radioactive activity of uranium series,thorium series and actinium series were mainly contributed by their daughter nuclide Ra-228,Th-224、Ra-226,Pa-231、Ac-227.The activity of tailing and the calculation formula of uranium,thorium and radium in the non-equilibrium state are obtained through the segmentation theory.The calculated results show that the total radioactive activity of acid soluble tailing is much higher than that of neutralization tailing,the average content of thorium and radium in acid soluble tailing is 420.55mg/kg、0.00029mg/kg,and the average content of uranium in neutralization tailing is 287.57mg/kg.（3）The MOF-76（Sm）was prepared by hydro-thermal synthesis,The MOF-76（Sm）samples were characterized by SEM,XRD and FTIR.Under the condition of room temperature,the adsorption properties and the adsorption mechanism of the samples were studied.The adsorption of Cs on MOF-76（Sm）was more satisfied with the second-order kinetics,mainly by chemical adsorption,and the maximum saturated adsorption capacity was 52.36 mg/g by fitting Langmuir isotherm.