Study On Adsorption And Separation Of Rubidium And Cesium Ion From Salt Lake Brine By Ammonium Molybdophosphate And Its Composite Ion

The rubidium and cesium resource is very rich in salt lake brine in our country, but theconcentration of rubidium ion（Rb⁺） and cesium ion（Cs⁺） in salt lakes is usually low. There areplents of potassium, sodium, magnesium, lithium ions coexisting in salt lake brine, whichbring a lot of difficulties in separation and extraction rubidium and cesium. Up to now, it isstill a worldwide problem to separate and purify rubidium/cesium from salt lake brineeconomically and feasibly.In this paper, the ammonium molybdophosphate（AMP） and ammonium molybdo-phosphate-zirconium phosphate-sillica（AMP ZrP SiO₂） composite were used in adsorptionof Rb⁺and Cs⁺from salt lake brine. The analysis method of trace Rb⁺and Cs⁺in salt lakeswas established in flame atomic absorption spectrometry. The influence of temperature, pHand other factors on the adsorption of Rb⁺and Cs⁺and the preparation technology of theabsorbents were investigated. The adsorption enthalpy（△H）, adsorption Gibbs freeenergy（△G）, activation energy（Ea） were studied. In addition, ammoniumphosphotungstate（AWP） adsorbents and precipitation method were also used in separationRb⁺and Cs⁺from salt lakes.The results show that AMP exhibits good efficiency on adsorption of both Rb⁺and Cs⁺from salt lake brine, and the reaction process is endothermic and spontaneous. The adsorptionenthalpy for Rb⁺、Cs⁺is38.01kJ/mol and70.72kJ/mol, respectively, indicating the favorableof adsorption of Rb⁺and Cs⁺on AMP at elevated temperature. The adsorption process of Rb⁺and Cs⁺is more suitable for Langmuiror monolayer adsorption. Column operation of AMP isdifficult because of its microcrystalline and poor hydraulics performance.By the group of HPO₄, AMP was combined to the surface of ZrP, then AMP ZrP wasfurther binded with SiO₂to producing AMP ZrP SiO₂. This new adsorbent is superior toAMP in adsorption performance because of its good hydraulics performance and suitable forcolumn operation. And adsorption enthalpy for Rb⁺and Cs⁺on AMP ZrP SiO₂is16.50kJ/mol and38.78kJ/mol, adsorption activation energy for Rb⁺and Cs⁺is84.51kJ/mol and57.75kJ/mol, respectively. The concentration of Rb⁺can be enrichmented10～25times ineluent by desorbing AMP ZrP SiO₂column with20%NH4Cl, achieving0.3～0.5g/L. Theconcentration of Cs⁺in eluent can achieve3～6times than the raw brine. Rb⁺and Cs⁺can beseparated by subsection receiving eluent. The concentration of magnesium, sodium,potassium can be reduced8～25times, which indicating that the effect of enrichment andseparation for Rb⁺and Cs⁺is good. AMP ZrP SiO₂can be used repeatedly. High purity RbCland CsCl can be obtained by extracting desorption liquid with t BAMBP and reverse cxtracting with HCl.