Extraction And Separation Of Rare Earth And Its Associated Elements By Amino Phosphine Extractant

With the rapid development of high-tech industries,the global requirements for the purity of rare earths and their compounds are increasing.Thus,how to extract and purify rare earths from rare earth minerals has become the focus of scientific researchers.Thorium and uranium are often associated with rare earth minerals due to their similar chemical properties.These radioactive elements are leached during the leaching process of rare earth ores,which affect subsequent extraction and separation of rare earths.Therefore,it is important to find a method to efficiently separate uranium and thorium from rare earths.Among the existing technologies for separating and purifying metals,the solvent extraction method has become an important method because of its high efficiency,simple equipment,high separation efficiency and large processing capacity.In this paper,the extraction and separation of rare earth and its associated elements thorium and uranium in sulfuric acid medium were studied.The main work as follows:1.The performance of selective extraction and separation of U???and Th???from sulfuric acid medium by?-aminophosphonate extractant di?2-ethylhexyl?[N-?2-ethylhexyl?aminomethyl]phosphonate?Cextrant 230,L?was studied.The extraction of uranium,thorium,rare earths,aluminum and other elements was compared under different acidity,The extraction order is:U???>Th???>Fe???>RE???>Al???,and the extraction rates gradually decrease with the increase of acidity.The uranium extraction was investigated in detail.The extraction mechanism was proposed to be a neutral complex mechanism and the extracted complex was inferred to be UO₂SO₄·2L,The influence of temperature on the extraction process was discussed,and the results showed that the extraction process was exothermic and spontaneous.The selective extraction and removal of uranium and thorium from a simulated leaching was investigated,it was found more than 99%of the radioactive U???and Th???were removed after a cross-flow extraction,which improved the subsequent extraction environment and avoid contamination of rare earth products.2.Rare earth was extracted from sulfuric acid medium by using?-aminophosphonic extractant?2-ethylhexylamino?methyl phosphonic acid mono-2-ethylhexyl ester?HEHAMP,H2A2?was studied.The effect of equilibrium acidity on the extraction of rare earth was investigated.The extraction order was consistent with that of most acidic extractants.The position of Y???fell between Ho???and Er???.The extraction order was as follows:Lu???>Yb???>Tm???>Er???>Y???>Ho???>Gd???>La???.The extraction mechanism was proposed to be a cation exchange mechanism and the extracted complex was RE?HSO4?2HA2 by the slope analysis method,which confirmed by infrared spectroscopy.Taking the heavy rare earths Yb???and Lu???as examples,the effect of temperature during the extraction process was investigated and the corresponding thermodynamic parameters were calculated.The results show that the reaction was an endothermic process.The loading capacity of 30%HEHAMP were 37.37g/LYb2O3 and 40.12g/LLu2O3,respectively.4mo/L HCl can effectively strip Yb???and Lu???from the organic phase into the aqueous solution,and the stripping rates are over 90%.