Solvent Extraction Separation And Kinetics Of Rubidium From Salt Lake Brine

Rubidium and cesium have excellent photoelectric properties and are important strategic resources.Salt Lake Brines in China are rich in rubidium and cesium,which have not yet been effectively exploited and utilized.With the comprehensive utilization of Salt Lake resources,it is imperative to separate and extract rubidium and cesium from brine.In this paper,solvent extraction method was used to separate and enrich rubidium in brine.A crown ether-ionic liquid extraction system with different side chains and pore sizes was constructed by introducing ionic liquids as synergist in traditional crown ether system.Four kinds of ionic liquids were synthesized by modifying four traditional phenol alcohol extractants.The extraction and separation performances of rubidium in different extraction systems were studied and compared.The factors affecting the extraction performance of the system were investigated in detail,and the extraction process was optimized.The extraction ratio of rubidium ion and extractant in each system was obtained by slope method.By means of ultraviolet and infrared spectroscopy,the changes of organic phase before and after extraction were analyzed,and the extraction mechanism of different systems was studied.The extraction thermodynamic process of each system was studied and the corresponding thermodynamic parameters were obtained.The structures of three crown ether extracts and four synthesized ionic liquids were optimized by quantum calculation,and the corresponding chemical bond lengths and binding energy parameters of anions and cations were obtained.The extraction kinetics of rubidium with t-BAMBP-SK system was studied by single drop method.The main conclusions are as follows:1.A system of 18C6-[C₄mim⁺][PF₆^-]-C₂H4Cl₂ was constructed.The optimum extraction conditions were determined by single factor variable method at 291K:V_IL=80%,water phase pH not adjusted,oscillation time 15 min,18C6 concentration 0.5mol L 1,compared with O/A=1.5.Under these conditions,the single-stage extraction rates of Rb⁺,Cs⁺,K⁺were 84.11%,94.99%and 36.45%,respectively.The system can remove 99.31%Na⁺and 49.7%K⁺effectively with mixed solution containing RbCl,CsCl and H₂SO₄.Rb⁺and Cs⁺are not lost in the washing process and have partial extraction.The single-stage stripping rates of 3.0 mol·L^-11 NH4NO3for Rb⁺,Cs⁺were 90.55%and 97.73%,respectively.The results of ultraviolet absorption and infrared spectroscopy analysis show that the system can extract Rb⁺,Cs⁺by cation exchange.Compared with traditional diluents,the introduction of ionic liquids into crown ether system can effectively improve the extraction efficiency of18C6 for rubidium and cesium,and can be used for the separation of rubidium and cesium in water phase.2.The extraction system of TB21C7-[C4mim⁺][NTf₂^-]-C₂H4Cl₂ was constructed by screening the pore size and side chain of crown ether and improving the synergist.When the temperature is 291K,VIL=90%,the oscillation time is 10min,the concentration of TB21C7 is 0.2 mol·L^-11 and the ratio of O/A=1.5,the extraction rates of Rb⁺,K⁺are 93.63%and 32.50%respectively.Compared with18C6-[C4mim⁺][PF₆^-]system,TB21C7-[C4mim⁺][NTf₂^-]system has a significant improvement in the separation coefficient of rubidium and potassium,and has better hydrophobicity and faster phase separation speed.The slope method was used to calculate the ratio of the extracted compounds to 1.06.The results of ultraviolet absorption spectrum and infrared spectrum analysis showed that ionic liquids extracted Rb⁺by cation exchange;O atom of TB21C7 ether oxygen bond formed coordination bond with M⁺;Quantum calculation showed that TB21C7 and Rb⁺bound in three crown ethers with different structures.The bond length is the shortest and the interaction with Rb⁺is much stronger than that with K⁺.Thermodynamic studies of extraction showed that the crown ether system was spontaneously exothermic for Rb⁺extraction.3.The separation and extraction technology of rubidium from brine by TB21C7-[C4mim⁺][NTf₂^-]-C₂H4Cl₂ system was studied.The optimum extraction conditions were obtained by orthogonal experiment,0.25 mol·L^-1extractant,2:1 ratio,274 K temperature and 10%diluent composition.After three-stage countercurrent extraction,the distribution of Rb⁺and K⁺increased to 130.58 and 0.718,respectively,and more than 99%Rb⁺was extracted into organic phase.The extraction process was effectively completed,and the separation of rubidium ion and most of the coexisting ions in brine was realized.The separation effect of coexisting metal cations showed that the system had little extraction of Li⁺,Mg²⁺,B,and some Na⁺,K⁺coexisted.Under the optimum composition and washing conditions,the mixed detergent could remove Na⁺and most K⁺,and Rb⁺could extract part of Rb⁺from the detergent after three times washing of the loaded organic phase.After stripping the loaded organic phase with 2.5 mol·L^-11 NH₄NO₃,only Rb⁺and K⁺were detected in the stripping solution.The ratio of K to Rb decreased from 104.3 to 0.12,and Rb⁺was enriched and separated.After five cycles of organic phase,Rb⁺still had good extraction performance.4.Four kinds of ionic liquids were synthesized by modifying four different side-chain phenolic alcohols:[N⁺₄₄₄₄][pTBP^-]?[N⁺₄₄₄₄][pTBNP^-]?[N⁺₄₄₄₄][sBAMBP^-]?[N⁺₄₄₄₄][tBAMBP^-].Among them,[N⁺₄₄₄₄][tBAMBP^-]is better than the other three.At 0.5 mol·L^-1,[N⁺₄₄₄₄][tBAMBP^-]yields of single-stage extraction of rubidium and potassium were 92.7%and 16.2%,respectively.Rb⁺in supported organic phase was stripped with 0.08 mol·L^-11 HCl.The single-stage stripping rate was more than 97%.The organic phase after stripping can be regenerated by alkali washing and water washing,and the extraction rate of Rb⁺is still more than 87%after four cycles of reuse.The extraction ratio of Rb⁺to ionic liquid-like molecule is 0.667,and the ratio of Rb⁺to ionic liquid-like molecule is 2:3.Infrared spectroscopy showed that the functional groups on[N⁺₄₄₄₄]did not react with Rb⁺in the extraction process.O atoms and Rb⁺on C-O formed C-O?Rb bonds on anion[RO^-].The synthesized ionic liquid-like system was a neutral compound mechanism.Compared with the corresponding phenolic alcohol extractants,the extraction efficiency of four kinds of ionic liquids for Rb⁺has been significantly improved.Compared with the crown ether-ionic liquids system,the four kinds of ionic liquids have better selectivity for Rb⁺than the corresponding phenolic alcohol extractants.5.The extraction kinetics of rubidium from t-BAMBP/sulfonated kerosene was studied using an improved single droplet device.The results showed that the extraction rate of rubidium indicated that the extraction reaction of rubidium from t-BAMBP occurred in the interface region.The extraction rate equation was obtained R_e=3.176×10^-5[Rb⁺]^1.002[OH^-]^1.179[t-BAMBP]^0.991,and the root mean square error between the experimental and calculated values was 2.581%.Thermodynamic studies show that the extraction reaction is exothermic and low temperature is favorable for the reaction.The apparent activation energy of the extraction reaction is Ea=10.43kJ·mol^-1,and the extraction process is controlled by expansion.The study of extraction rate by coexisting ions shows that the competitive preemption of K⁺leads to the decrease of extraction rate of Rb⁺and the existence of Mg²⁺,Ca²⁺and borate ions reduces the extraction rate of Rb⁺while Li⁺has almost no effect on the extraction rate of rubidium.In the high concentration Na⁺environment,the extraction rate of rubidium is about 1/3 of that in the Na⁺free environment.The steady-state approximation method was used to deal with the mass transfer equation in the extraction process,and the extraction rate reaction equation was consistent with the macro-kinetic equation obtained from the experiment.In a word,through the construction and optimization of crown ether-ionic liquids system,Rb⁺can be effectively separated and separated from brine by extracting,washing and stripping.The modification of traditional phenol-alcohol system solves the problem that the traditional phenol-alcohol system needs to simplify the water phase,and improves the problem of slow phase separation and easy emulsification.The extraction kinetics of rubidium in t-BAMBP-SK system will be further studied,which will provide theoretical guidance for the expanded experiment of the system.