Efficiently removal the lanthanides using electroreduction diffusion method/high-temperature adsorption technique

The consumption of electricity and the price of molten salt are key factors that limit the pyroprocessing of nuclear fuel. This paper proposes a strategy to reduce costs associated with pyroprocessing of spent fuel by combining electrolytic refining and molecular sieve adsorption for fission product removal and radioactive waste salt recovery. Firstly, we investigated the electrochemical process of ytterbium on a gallium film electrode in LiCl-KCl using various methods, calculating its kinetic parameters at different temperatures. Potentiostatic electrolysis experiments were conducted at 773 K, resulting in the formation of Ga-Yb alloy as the electrodeposited product with a ytterbium removal rate reaching 93.78 %. Then, we studied the adsorption behavior and mechanism of ytterbium through electrorefining combined with molecular sieve adsorption. Experimental results showed that the extraction rate achieved more than 99.99 %, significantly reducing electrolysis costs while increasing target nuclide removal rates. Finally, we investigated the molten salt adsorption mechanism using molecular sieves, identifying chemical ion exchange as the primary mechanism based on recalibration using pseudo-first-order, pseudo-second-order, and Weber-Morris kinetic models. In conclusion, combining electrodeposition and high-temperature adsorption provides an effective approach for recovering and utilizing waste salt in pyroprocessing.