A novel adsorbent potassium magnesium ferrocyanide for selective separation and extraction of rubidium and cesium from ultra-high salt solutions

The unique properties of rubidium and cesium make them occupy a place in high-tech applications. In this paper, a novel adsorbent (potassium magnesium ferrocyanide—KMgFC) was synthesized and used to recover rubidium and cesium from ultra-high salt solutions. The composition of the material phase was determined to be K2.01[Mg0.97Fe(CN)6]‧xH2O by characterization and analysis of KMgFC. The effects of various factors on the extraction rates of Rb+ and Cs+ were investigated, and the results exhibited that the extraction rates of Rb+ and Cs+ could reach 90.7 % and 97.9 % at a reaction pH of 8.1, a temperature of 80 °C, an adsorbent dosage of 3 times the theoretical dosage, and an equilibrium time of 40 min. The equilibrium adsorption capacities of KMgFC for Rb+ and Cs+ were 158.91 mg/g and 8.11 mg/g, respectively. Furthermore, the mechanism analysis displayed that the structure of KMgFC changed slightly during the adsorption process, and the ion exchange process between Rb+ or Cs+ and K+ occurred to achieve the capture of Rb+ or Cs+. Based on the strong affinity for Rb+ and Cs+, KMgFC is expected to be a viable adsorbent to be applied for the selective recovery of rubidium and cesium.