Efficient Enrichment of Rubidium and Cesium from High-Salt Solution by Copper Hexacyanoferrate Co-Precipitation

Graphical In this study, copper hexacyanoferrate (CsRb–CuHCF) was used as a precipitant. Results demonstrated that CsRb–CuHCF can efficiently separate Rb + and Cs + from the high-salty solutions. The enrichment factor was up to 384 before and after precipitation. The precipitant reacts first with Cs + and then gradually with Rb + and can be used for the separation of Cs + and Rb + from each other. Cesium (Cs) and rubidium (Rb) are important rare alkali metal elements that are scarce and dispersed in nature. They often coexist with high amounts of Na + and K + . In this study, copper hexacyanoferrate (CuHCF) was used as a co-precipitant to enrich Cs + and Rb + in a high-salt solution. The effect of parameters, such as type and dose of divalent metal ions, solution pH, material dropping speed, reaction time, and temperature, was investigated for the recovery rate of Cs + and Rb + . Results showed that the recovery rates of Cs + and Rb + were 99.78% and 88.84% at the optimal Cu 2+ /(Cs + +Rb + ) molar ratio of 0.5, respectively. The reaction could be completed within 10 min in pH 3–8. The detailed characterization of the Cs + and Rb + containing co-precipitants, CsRb–CuHCF, confirm a general formula of Cs 1.09 Rb 0.81 K 0.16 Cu 0.97 Fe(CN) 6 . The (Cs + +Rb + )/(Na + +K + ) increased significantly from 0.074 to 28.47 before and after precipitation, which realized the effective enrichment of Cs + and Rb + . Studies of the precipitation reaction mechanism showed that the precipitant reacted first with Cs + and then with Rb + . This process offers a promising avenue for the enrichment and separation of Cs + and Rb + from high-salty solutions.