Electrochemical extraction of rubidium from salt lake by using cupric ferrocyanide based on potassium shuttle

Abstract

Extracting rubidium from high reserve salt lakes has been an important measure to cope with the growing demand for rubidium. However, due to the low concentration and high impurity ions in the salt lake, there was no rational method to extract rubidium. Prussian blue and its analogues (PBAs) with specific functional structures have shown good cycling stability for K+ and Rb+ with large ionic radii in the field of batteries and their special affinity (Li+ > Na+ > K+ > Rb+) for rubidium, which provides a new idea for the extraction of rubidium from salt lakes. In this paper, the cyclic electrochemical performance of synthesized copper ferricyanide (Cu3[Fe (CN)6]2) for rubidium was tested. Furthermore, a new method of rubidium extraction from salt lake was proposed by using potassium as the shuttle ion. The (K2Cu3[Fe (CN)6]2) obtained by intercalating K+ into copper hexacyanoferrate (Cu3[Fe (CN)6]2) with the electrochemical method was used to extract rubidium from simulated brine and the separation coefficients βRb: K, βRb: Na, βRb: Ca and βRb: Mg were 63, 1635, 585 and 2543, respectively. After that, rubidium was deintercalated by electrochemical oxidization of Rb2Cu3[Fe (CN)6]2 and the deintercalated efficiency can be reached 98 %. Rubidium enrichment can be achieved by repeating the above process with regenerated materials.