Study On Leaching Mechanism Of Radioactive Element Uranium And Thorium In Ta-Nb Slag With High Fluorine And Strong Acid

Ta-Nb ore belongs to rare metal minerals and is mostly used in high-tech and national defense fields.Because it contains radioactive elements such as uranium and thorium,and it’s smelting process is special,it enriches more radioactive elements in the waste slag produced in the smelting process of Ta-Nb ore.If improperly disposed and preserved,it may cause environmental pollution and waste of resources to a certain extent.Recycling and reusing radioactive elements such as uranium and thorium in tantalum-niobium slag can achieve the goal of recycling,reducing,environmental protection and centralization of waste slag.（1）Based on the leaching rules of uranium and thorium in the conventional nitric acid leaching process and sulfuric acid leaching process,the phase characteristics of tantalum-niobium slag with high fluorine and strong acid are obtained by combining the research methods of related process mineralogy and material science,and the optimum leaching conditions of uranium and thorium in the acid leaching process are confirmed.On this basis,the relevant knowledge of hydrometallurgy is used to clarify the leaching kinetics and thermodynamics.The leaching characteristics of radioactive element uranium and thorium in acid leaching process were studied,and the kinetic equation of acid leaching process was improved by fitting the leaching rate and related parameters respectively.（2）This arctical through a series of characterization of tantalum-niobium slag,the related characterization includes particle size analysis,X-ray diffraction analysis,infrared spectrum analysis,thermogravimetric analysis,specific surface area pore size analysis,X-ray fluorescence spectrometry analysis,inductively coupled plasma mass spectrometry analysis and so on.It is concluded that the uranium element in tantalum-niobium slag is2.845×10³ mg/kg,and the content of thorium element is 9.030×10³ mg/kg.The comprehensive analysis of the above characterization shows that the tantalum-niobium slag is not made up of one metal oxide or salt.The tantalum-niobium slag is composed of many metals and non-metals,and the associated uranium-tantalum radioactive elements are enriched tailings.（3）In order to recover uranium and thorium from tantalum-niobium slag,a series of technological explorations have been carried out,to ensure the maximum recovery of uranium and thorium from tantalum-niobium slag,including sulfuric acid leaching experiment and nitric acid leaching experiment,temperature（40–80℃）and time（1–8hours）.Solid-liquid ratio（1:1–12:1）,concentration（0–8 mol/L）,particle size（microwave,non-microwave）were studied to analysis the leaching law of uranium and thorium leaching rate changing with conditions in a certain range.The leaching efficiency of tantalum and niobium slag with 4 mol/L sulfuric acid was the highest,the leaching rate of thorium reached69.76%,and the leaching rate of uranium was 51.03%.（4）Combining the analysis of Shrinking core model（SCM）and Arrhenius equation,the leaching kinetics of uranium and thorium from tantalum-niobium slag is obtained.The leaching reaction of uranium and thorium from tantalum-niobium slag with sulfuric acid and nitric acid conforms to the shrinking unreacted core model,which belongs to chemical control.When the temperature is raised to a certain extent,the reaction rate will be accelerated accordingly.The kinetic equation is:1-（1-x）^1/3=kt and the activation energy of chemical leaching reaction is calculated.This process can greatly reduce the radioactive element uranium in the tantalum-niobium slag and reduce a certain degree of environmental pollution.In addition,according to the leaching mechanism and conditions of tantalum-niobium slag,a series of suggestions are proposed for the subsequent process.