Distribution and evaporation characteristics of Rb and Cs in complex salt brine systems

Abstract

The brine in salt lakes is rich in resources, including not only K, Mg, and B, but also valuable trace elements. During the enrichment and extraction of trace elements (Rb, Cs) from carbonate type salt lake brines, the process is significantly influenced by the presence of other coexisting ions such as Li⁺, K⁺, and Mg²⁺.The physical and chemical properties of K⁺ are extremely similar to those of Rb⁺ and Cs⁺, and its impact on the extraction of Rb⁺ and Cs⁺ is particularly significant. When K⁺, Rb⁺, and Cs⁺ coexist, they can form solid solutions such as [(K, Rb)₂SO₄], [(K, Cs)₂SO₄], and [(Rb, Cs)₂SO₄]. The formation of these solid solutions can lead to severe losses of Rb and Cs during the evaporation process of the brine, resulting in low yield. In response to the aforementioned issues regarding the evaporation process of Rb and Cs, this paper uses the aqueous-salt system phase diagram as a guide and combines experimental research with simulation calculations to study the enrichment patterns of trace elements Rb and Cs in the Na⁺, K⁺//Cl⁻, CO₃²⁻, SO₄^2--H₂O aqueous-salt system, as well as the migration mechanism of Rb and Cs.