Molten Salt/liquid Metal Reductive Extraction Of Rare Earth And Anodic Dissolution Of Al-Gd Alloys

The spent fuel reprocessing is one of the key technologies to make full use of uranium,ensure sustainable development of nuclear energy and protect the environment.Using spent fuel reprocessing can significantly reduces the volume and toxicity of radioactive waste.Molten salt/liquid metals reductive extraction and electrolytic refining are considered as one of the most promising dry reprocessing technique.Therefore,the separation of rare earth elements is carried out using molten salt/liquid metal reduction extraction and electrolytic refining.In the CaF₂-LiF melts,the extraction of rare earth elements from molten salt was performed using liquid Pb-Li,Bi-Li and Al-Li as reducing extractant.Meanwhile,electrorefining of Al-Gd alloy was studied in KCl-LiCl molten salt.The detailed is as follows:1.At a temperature of 1123 K,the reductive extraction of rare earths?Sm,Eu,Ce?were conducted in CaF₂-LiF molten salt/liquid metal?Pb-Li,Bi-Li or Al-Li?system.First,square wave voltammetry was used to measure the relationship between the reduction peak current and the concentration of rare earth ions in molten salts,and calibration curves for rare earth ions were plotted.Then,the extraction process of Sm,Eu,and Ce was studied in CaF₂-LiF molten salt system with different extractants,respectively.And the change of rare earth ion concentration with extraction time was monitored using calibration curves in the reductive reduction of RE?Sm,Eu,Ce?in LiF-CaF₂-RE³⁺/liquid metal?Pb-Li,Bi-Li or Al-Li?system.Meanwhile,the effects of different extractants on extraction results were also studied.The extraction efficiency and extraction rate of different rare earths were estimated.2.At 873 K,the anodic dissolution of Al-Gd alloy was investigated by cyclic voltammetry,square wave voltammetry,anodic polarization curve and Tafel curve methods in KCl-LiCl molten salts.The dissolution potential and the degree of dissolution of the alloys with different compositions were explored using cyclic voltammograms and square wave voltammograms obtained at different dissolution time.The polarization curve was used to determine the corrosion potential and corrosion behavior.The exchange current density was calculated by Tafel curves at different temperatures.Meanwhile,the influence of anodic potential and different dissolution time on the anodic dissolution was discussed.The alloys after anodic dissolution under different conditions were characterized by XRD and SEM.The anodic dissolution process of Al-Gd alloys was emphatically analyzed.3.Electrorefining of Al-Gd alloys was studied.Under different electrolytic conditions,such as different current intensities,electrolysis times,or working electrodes,etc.,metallic aluminum was electrochemical extracted.The effects of electrolytic refining of Al-Gd alloys were discussed and the current efficiency was also calculated.