Synthesis Of Aminophosphine Extractant And The Applications In Separation Of Cerium,Thorium And Rare Earths

Rare earth elements are widely used in petrochemical,aerospace,electronic information,national defense and other fields because of its unique physical and chemical properties.With the rapid development of innovative industries and modern high-tech,the performance of advanced rare earth materials has been put forward higher requirements,and the demand for high purity rare earth is increasing.As one of the world's largest producers of rare earths,China not only has large reserves of rare earths,but also a rich variety of minerals,accounting for 90 percent of the global supply of rare earths.However,due to the large amount consumption of acid and alkali during the separation progress of rare earths,which will lead to a large amount of salty wastewater discharge,China's rare earth industry is facing serious environmental problems due to these problems.Therefore,it is very important to develop efficient,clean and green rare earth purification technology.In the process of hydrometallurgy,a suitable extractant has always been the focus of research during the extraction and separation of rare earth ions.In this paper,N atom was introduced into phosphine extractant to synthesize nitrogen-containing amine-phosphine bifunctional extractant,which was applied to the separation and purification of cerium???,thorium???and rare earths???.The main research contents are as follows:1.A new aminophosphine extractant was synthesized:?-aminophosphine extractant?DEHAPO?,which was applied to the separation and purification of cerium???,thorium???and rare earths???,the influence of the concentration of the extractant,the concentration of sulfuric acid and temperature on the extraction of cerium???was studied.The experimental results shown that cerium???can be well separated from thorium???and rare earths???under low acidity,and the extraction performance of DEHAPO was compared with that of traditional extractants,which shown a better extraction and separation capability for cerium???.The method of slope analysis was used to prove that the extraction complex of Ce???was Ce?HSO₄?₂SO₄·DEHAPO.The thermodynamics of the extraction process was studied,?H is-27.95 k J/mol,?H is less than 0,indicating that the extraction process was an exothermic reaction.The back-extraction experiments shown that the cerium ions loaded in the organic phase can be back-extracted at lower acidity,which will further reduce acid consumption.In DEHAPO's saturated load and cyclic test experiments,it was found that the saturated load capacity of 30%?v/v?DEHAPO was about 16.66 g/L Ce O₂,and the extraction efficiency of DEHAPO did not change significantly after 6cycles.Therefore,the extraction process may provide an effective method to separate Ce???,Th???and REs???well in sulfuric acid medium.2.According to previous studies,DEHAPO has a certain extraction capacity for thorium???under a certain acidity,so the influence of the concentration of sulfuric acid,the concentration of extractant and temperature was further studied on the extraction and separation capacity of thorium???and rare earths???.In order to improve the extraction capacity of the extractant,the influence of the concentration of the extractant on the extraction capacity was studied.According to the experimental results,when the concentration of the extractant was 0.2 mol/L,a better extraction result could be obtained.The concentration of sulfuric acid was about 0.1 mol/L,DEHAPO had a high extraction capacity for thorium???,the extraction rate reached the maximum,and it can separate thorium???from rare earths???well.The thermodynamics of the extraction process was studied,?H is-24.64 k J/mol,and the negative?H indicated that the extraction process of thorium was an exothermic reaction.The extraction complex of Th???was Th?HSO₄?₂?SO₄??2DEHAPO,the extraction mechanism was further verified by infrared spectroscopy and nuclear magnetism.The back-extraction experiments shown that Th???loaded in the organic phase can be back-extracted at low acidity.Therefore,DEHAPO can effectively separate Th???and REs???in sulfuric acid medium.