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Separation among rubidium and potassium ions from salt lake brines remains challenging. In this work, a typical room temperature ionic liquid 1-ethyl-3-metyhlimidazaolium bis(trifluoromethylsulfonyl)imide ([C2mim+][NTf2–]) was used as diluent and synergistic extractant, dicyclohexano-18-crown-6 (DCH18C6) was used as extractant to extract rubidium ions from brine solutions which contain high concentrations of potassium ions was investigated. Under the optimal conditions, the single extraction efficiency of rubidium ions was up 93.63%. The thermodynamic parameters of the rubidium ion extraction were obtained. Based on the slope analysis method, the extracted species in the organic phase were ascertained as 1:1 complex. UV-visible has been performed to investigate the ion concentration of ionic liquid before and after the interaction of metal ions and ligands. Rubidium ions in [Rb · DCH18C6]+ complex were stripped by 2.5 mol · L–1 NH4NO3. The extraction system offers high efficiency, simplicity and environmentally friendly application prospect to separate rubidium from brine solutions.

Application of 1-butyl-3-metyhlimidazaolium hexafluorophosphate ([C4mim][PF6]), in the extraction of rubidium and cesium from brine solutions using 1,4,7,10,13,16-hexaoxacyclooctadecane (18C6) as extractant was investigated. Parameters that affect the extraction including pH of aqueous phase, equilibration time, dosage of the ionic liquid, phase ratio, concentration of 18C6 were studied. Under the optimal conditions, the single extraction efficiency of rubidium ions and cesium ions were up 84.11% and 94.99%, respectively. The stripping of alkali metal ions from the loaded organic phase with different stripping agents and concentrations were also investigated. The initial value of the K/Cs and K/Rb ratios were 93.0 and 104.3, respectively, which have dropped 91.21% and 88.01%, respectively, after the extraction and stripping experiments. It was taken a big step in the separation and enrichment of cesium (rubidium) ion and potassium ion. The extraction mechanism was revealed most likely to be a cation exchange mode in this system.

Graphical abstract The extraction kinetics of rubidium by t-BAMBP/sulfonated kerosene from brine solutions was investigated by rising single drop method. The extraction process is controlled by the diffusion and the chemical reaction takes place at the interfacial area and bulk phase. The rate of Rb+ by t-BAMBP in the investigated system is closed to first-order with respect to [Rb+], [H+] and t-BAMBP. A model of mass-transfer process of reactants with a rising single drop method was established and the mechanism of rubidium extraction with t-BAMBP/sulfonated kerosene was proposed. Highlights • Extraction kinetics of Rb+ by t-BAMBP/SK from brine solutions was investigated. • Extraction process is controlled by the diffusion. • A mass transfer model for extractants was established. • The mechanism of the rubidium extraction with t-BAMBP/SK was proposed. Abstract Kinetics of rubidium extraction by 4-tert-butyl-2-(α-methylbenzy) phenol (t-BAMBP)/sulfonated kerosene in brine solutions were investigated using the rising single drop technique. Parameters affecting the mass transfer mechanism, including the interfacial area, initial alkalinity of aqueous phase, concentration of rubidium ions and t-BAMBP, and temperature were studied. The results indicated that the process of extraction was controlled by the diffusion process, while the chemical reaction occurred at the interfacial area. Dynamic equation of the extraction system, R e = 2.901 × 10−5[Rb+]1.022[OH−]1.179[t-BAMBP]0.991 was obtained by non-linear fitting the experimental data. Moreover, a new mechanism of the rubidium extraction with t-BAMBP/sulfonated kerosene was proposed. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel composite adsorbent of sodium tetraphenylborate – polyacrylonitrile (TPB–PAN) was prepared for investigating adsorption behaviors of rubidium (Rb) and cesium (Cs) ions from their aqueous solutions. Several experimental parameters such as pH, shaking time, initial concentration, and interference ions were routinely evaluated. The experimental results showed that the Rb(I) and Cs(I) were both adsorbed by the adsorbent of TPB‐PAN at pH 7.0, and the adsorption equilibriums were achieved within 2 h. The presence of co‐existing ions did not get involved with Rb(I) and Cs(I) adsorption, indicating the high selectivity of TPB‐PAN adsorbent toward Rb(I) and Cs(I) ions. Under optimum conditions, the maximum adsorption capacities for Rb(I) and Cs(I) ions by the adsorbent of TPB‐PAN were 44.64 mg g−1 and 118.48 mg g−1 based on the langmuir sorption isotherm study. In addition, the adsorption processes of rubidium and cesium both are exothermic spontaneous process. Therefore, the proposed adsorbent of TPB‐PAN allowed the selective, sensitive, easy to use, cost‐effective, high efficiency, fast kinetics of preconcentration and separation (removal) Rb(I) and Cs(I) ions even in the presence of competing ions. As a consequence, the TPB‐PAN adsorbent can be used potentially for preconcentration and separation Rb(I) and Cs(I) ions from water samples in a wide range of practical applications for removal Rb(I) and Cs(I) ions in environmental aqueous resources. [ABSTRACT FROM AUTHOR]

Abstract: In this study, a novel composite adsorbent of ammonium phosphomolybdate – polyacrylonitrile (AMP–PAN) was prepared for sensitive and selective preconcentration and separation of rubidium (Rb(I)) ion from salt lake brine. Several experimental parameters, such as pH value, shaking time, concentration, interference ions, regeneration, stability and reusability were systematically investigated. The experimental results clarified that the Rb(I) ion was adsorbed by the adsorbent of AMP‐PAN at pH 7. Under optimum condition, the maximum sorption capacity for Rb(I) ion by the adsorbent was 500 mg g−1 based on the Langmuir adsorption isotherm study. The adsorption equilibrium was achieved within 2 h. The presence of co‐existing ions did not interfere with Rb(I) adsorption, indicating the high selectivity toward Rb(I) ion. The desorption results demonstrated that Rb(I) ion adsorbed the composite adsorbent of AMP‐PAN could be effectively desorbed by 0.5 mol L−1 NH4Cl and regenerated into the initial form without significant deterioration in its original functionality at the same time, which exhibited good stability of the adsorbent. Therefore, the proposed adsorbent of AMP‐PAN allowed the sensitive, selective, easy to use, cost‐effective, high efficiency, fast kinetics, stable and reusability preconcentation and separation of Rb(I) ion even in the presence of competing ions. As a consequence, the AMP‐PAN adsorbent can be used potentially to preconcentration and separation of Rb(I) ion from water samples in a wide range of practical applications for extracting Rb(I) ion in environmental aqueous resources. [ABSTRACT FROM AUTHOR]