Preparation Of Organic Phosphate Ester Extract Resin And Evaluation Of Lithium Extraction Performance

With the development of new energy batteries and electric vehicles,the demand for lithium resources in today’s society is increasing.China is rich in lithium resources,most of which come from salt lake brine,and salt lake lithium resources generally have the characteristics of high magnesium-lithium ratio.The chemical properties of lithium and magnesium are similar,so it is difficult to separate and extract lithium resources.TBP（tributyl phosphate）-FeCl₃ liquid-liquid extraction system is a relatively common salt lake lithium extraction method in industrial production,but a series of problems caused by high acidity reverse extraction have not yet been solved.Extract resin is an efficient and environmentally friendly separation technology that improves extractant loss and extraction kinetics through resin materials.In this paper,a TBP-P204-FeCl₃ ternary liquid-liquid extraction system was constructed,and the extractant was obtained on this basis,the extract resin was prepared by vacuum perfusion to investigate the separation of Li⁺in high magnesium-lithium ratio brine,the main contents are as follows:（1）Simulated brine with high Mg/Li ratio was used as the feed liquid,the extraction effect of TBP-FeCl₃ liquid-liquid extraction system on Li⁺was first investigated,and on this basis,P204（bis（2-ethylhexyl）phosphate）was screened as an additive,and the effects of comparison,Fe/Li molar ratio,inverse extraction phase and other factors on the extraction effect were investigated.By ultraviolet expression of the existence of ions in the organic phase,the extraction mechanism of Li⁺was proposed.The results showed that:Under the conditions of 30%TBP+70%sulfonated kerosene,oil/water ratio of 2 and Fe/Li molar ratio of 1.3,the extraction rate of Li⁺can reach more than 60%after one extraction with TBP-FeCl₃ system,when the partition coefficient D_Li was 1.75,D_Mg was0.03,and the separation factorβ_Li/Mg could reach 65.97.When the concentration of hydrochloric acid in the reverse phase was higher than 4 mol/L,it had a good separation and extraction effect on Li⁺.After adding P204,the use of pure water in the reverse extraction phase can avoid the loss of Fe³⁺,according to the optimization of the extraction conditions,the organic phase composition was 70%TBP+10%P204,compared with O/A=2,the extraction rate of Li⁺was 53.38%,β_Li/Mg reached 69.15,Li⁺was extracted into the organic phase in the form of Li（TBP）₂[FeCl₄]during the extraction process,P204 had almost no extraction effect on Li⁺.Due to the low concentration of Cl^-in pure water,the FeCl₄^-structure was broken,Li⁺entered the aqueous phase and was reversed,while Fe³⁺was retained in the organic phase with FeCl₂L（HL）·2TBP.（2）Based on TBP-P204-FeCl₃ liquid-liquid extraction system,Fe³⁺loading was first prepared into the organic phase by extraction,and then the extractant was loaded on AB-8 macroporous resin by vacuum perfusion method to prepare AB-TP extract resin.The chemical composition and surface morphology of the resin were analyzed by infrared and scanning electron microscope characterization,and the static adsorption behavior of AB-TP extract resin on Li⁺was studied,and the preparation conditions of the extract resin were optimized through the adsorption results,and the mechanism of adsorption of Li⁺by AB-TP extract resin was analyzed.The results showed that the AB-TP_0.5 extract resin prepared by the extractant containing 80%TBP-20%P204+30 g/L Fe³⁺showed good adsorption effect on Li⁺under the condition of 50%mass fraction of the extractant,and the equilibrium adsorption amount of Li⁺in the simulated brine was 5.8 mg/g.The kinetic studies showed that the adsorption behavior of lithium by resin conforms to the quasi-secondary kinetic model,and the internal diffusion model simulation further verifies that internal diffusion was not the main factor controlling the reaction.The adsorption of Li⁺by AB-TP_0.5 resin conforms to Freundlich model.（3）The old halide is generally the factory waste after production and concentration,which contains relatively high concentration of Li⁺and a variety of other cations.In this chapter,the separation and extraction effect of TPP-P204-FeCl₃ ternary extraction system on Li⁺under the condition of coexistence of multiple cations was investigated through liquid-liquid extraction.The static adsorption experiment of AB-TP_0.5 resin on simulated old halide was conducted to investigate the separation and extraction effect of resin on Li⁺under the condition of coexistence of various ions.Then,the dynamic adsorption and desorption conditions of AB-TP_0.5 resin on simulated old halide in salt lake were optimized,and the stability of the resin was investigated by cyclic experiments.The experimental results showed that the ternary liquid-liquid extraction system can preferentially extract Li⁺in the presence of Mg²⁺,Na⁺and K⁺.Dynamic adsorption experiments showed that the flow rate of adsorption liquid,resin filling amount and adsorption method would all affect the adsorption equilibrium capacity,and the resin still maintained high adsorption performance after six cycles.Through infrared characterization,it was verified that the extractant in the resin was not lost at this time,and the extraction resin had a certain stability.