Separation And Extraction Of Low Concentration Rb (Cs) From Salt Lake Brine

In this study,the solvent extraction,precipitation and adsorption methods were used to separate and extract rubidium and cesium in the system of simulated brine and raw brine which were studied.The extraction mechanism of rubidium and cesium by the system of 4-tert-butyl-2-（α-methylbenzyl）phenol（t-BAMBP）and sulfonated kerosene（SK）is studied from the quantum chemistry point of view.And,the influcing factors and precipitation kinetics of rubidium precipitation by phosphotungstic acid（PWA）were investigated.At the same time,several adsorption materials of rubidium and cesium were selected and prepared,and the adsorption performance and adsorption mechanism were in-depth studied.1.According to the previous work of our research group,the system of4-tert-butyl-2-（α-methylbenzyl）phenol（t-BAMBP）and sulfonated kerosene（SK）were used to separate and extract rubidium（cesium）from salt lake brine,and the suitable separation process was developed.The main influencing factors were studied respectively,the optimum process conditions were determined,and repeated extraction-stripping operation could achieve the purpose of separating and purifying rubidium from salt lake brine.In addition,it was proved that t-BAMBP can be recycled and has no obvious decrease on the extraction ability of rubidium（cesium）.Also,the molecular clusters of metal ions combined with t-BAMBP were established by Chemsketch software.Based on these molecular theoretical models,the PM7semi-empirical method was used to calculate by MOPAC 2016 software.According to the calculation results,both extraction reactions of rubidium and cesium by t-BAMBP are exothermic and occur spontaneously at 293 K.The 2:3 of ratio between alkali metal ion and t-BAMBP is more accurate description the reaction mechanism,rubidium and cesium ions reaction with t-BAMBP are easier than potassium ion.The calculated results are in good agreement with the experimental results,demonstrating that t-BAMBP is specific for rubidium and cesium.The combination of quantitative calculation with experimental result has great significance for the determination of extraction process and provides theoretical guidance for separation and extraction rubidium and cesium from salt lake brine.2.A novel phosphotungstic acid（PWA）precipitation method was established for separation and extraction rubidium from its aqueous solution.The concentration of rubidium in the filtrate was determinated by atomic absorption spectrometry（AAS）and the precipitate was analyzed by gravimetric method.In order to completely convert rubidium ions into precipitated form of phosphotungstate,the effects of precipitant dosage,pH,contact time,temperature and interfering ions on precipitation process were investigated.In addition,the study of precipitation kinetics shows that the precipitation reaction is a low temperature favorable reaction,the activation energy E_a=31.56 kJ mol^-1.The results of 10 repeated experiments show that the method of phosphotungstic acid（PWA）precipitation has good reproducibility,and the relatively consistent results were obtained by atomic absorption spectrometry（AAS）analysis and gravimetric method.The study of phosphotungstic acid（PWA）precipitation method has theoretical guidance for separation and extraction of rubidium（cesium）from salt lake brine,and provides great scientific value and economic significance for exploition and utilization of rubidium（cesium）resource in salt lake brine.3.A novel composite adsorbent of silicotungstic acid-polyacrylonitrile（STA-PAN）was prepared for investigating adsorption behaviors of rubidium（Rb）and cesium（Cs）ions from their aqueous solutions.The adsorption of STA-PAN adsorbent was characterized by SEM,EDS and FT-IR.Several experimental parameters such as pH,shaking time,initial concentration of Rb（I）and Cs（I）ions and interference ions were routinely studied in detail.The experimental results clarified that Rb（I）and Cs（I）ions were adsorbed by the adsorbent of STA-PAN at pH 7.0,and adsorption equilibrium was achieved within 2.5 h.The Rb（I）and Cs（I）ions adsorbed by STA-PAN adsorbent in accordance with the Freundlich adsorption isotherm,and the adsorption processes both were exothermic spontaneous process at 293 K.The desorption results demonstrated that Rb（I）and Cs（I）adsorbed onto composite adsorbent of STA-PAN could be effectively desorbed by 0.2 mol L^-1 HCl and regenerated into the initial form without significant deterioration in its original functionality at the same time,which exhibited good stability and recyclability of the adsorbent.Therefore,the STA-PAN composite adsorbent is suitable for separation of Rb（I）and Cs（I）ions from water resources and removal of them from wastewater.4.A novel composite adsorbent of sodium tetraphenylborate-polyacrylonitrile（TPB-PAN）was prepared for investigating adsorption behaviors of rubidium（Rb）and cesium（Cs）ions from its aqueous solutions.The adsorption of TPB-PAN adsorbent was characterized by SEM,EDS and FT-IR.Several experimental parameters such as pH,shaking time,initial concentration of Rb（I）and Cs（I）ions 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,the adsorption equilibrium was achieved within 2 h and conformed to pseudo-second-order adsorption kinetic model and which is indicated chemical adsorption.Under optimum conditions,the maximum adsorption capacity 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 from their aqueous solution which in the absence of potassium ion interference.As a consequence,the TPB-PAN adsorbent can be used potentially to 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.5.A novel composite adsorbent of ammonium phosphomolybdate-polyacrylonitrile（AMP-PAN）was prepared for sensitive and selective preconcentration and separation of rubidium and cesium ions from salt lake brine.The adsorption of AMP-PAN adsorbent was characterized by SEM,EDS and FT-IR.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）and Cs（I）ions were adsorbed by the adsorbent of AMP-PAN at pH 7.0,and adsorption equilibrium was achieved within 2.5 h.The presence of co-existing ions did not interfere with Rb（I）and Cs（I）adsorption,indicating the high selectivity toward Rb（I）and Cs（I）ions.The desorption results demonstrated that Rb（I）and Cs（I）adsorbed onto 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）and Cs（I）ions 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）and Cs（I）ions from water samples in a wide range of practical applications for extracting Rb（I）and Cs（I）ions in environmental aqueous resources.In summary,the specific extraction mechanism of rubidium and cesium by4-tert-butyl-2-（α-methylbenzyl）phenol（t-BAMBP）was explained from the perspective of quantum chemistry;the precipitation performance and kinetics of rubidium by phosphotungstic acid（PWA）were preliminary investigated;silicotungstic acid-polyacrylonitrile（STA-PAN）,sodium tetraphenylborate-polyacrylonitrile（TPB-PAN）and ammonium phosphomolybdate-polyacrylonitrile（AMP-PAN）were prepared using a precipitant capable of precipitating rubidium and cesium as a substrate.These adsorbents had better adsorption capacity toward cesium,and the order of adsorption performance of the adsorbent was:AMP-PAN>TPB-PAN>STA-PAN.In addition,AMP-PAN adsorption method showed a good performance on the separation of rubidium from raw brine.However,in the actual production and application,a single separation and extraction method often fails to meet the requirements,and multiple technologies need to be used together,which not only overcomes the shortcomings of function by oneself,but also is the future development trend of separation technologies.