Extraction Of Lithium From Lithium-rich Aluminum Electrolyte By PVC-H_1.6Mn_1.6O₄ Lithium Ion-sieve Membrane

Lithium and its compounds are widely used in various industrial fields.The consumption and demand for lithium in the Chinese market are increasing year by year.So,it is particularly important to explore new lithium ore resources.In domestic aluminum industry,a large number of bauxite containing lithium are mined and used to prepare metallurgical grade alumina.After long-term operation of aluminum reduction cell,aluminum electrolyte forms lithium-rich aluminum electrolyte due to the enrichment of lithium.Extracting lithium from lithium-rich aluminum electrolyte can not only supplement the market demand for lithium resources,but also realize the resource utilization of lithium-rich aluminum electrolyte.Among the technologies of extracting lithium from Salt Lake,spinel-type lithium ion-sieve H_1.6Mn_1.6O₄ is currently a promising lithium ion adsorbent.In this paper,through the combination of the acid leaching digestion of lithium-rich electrolyte and the absorption method,the PVC-H_1.6Mn_1.6O₄ ion-sieve membrane was prepared and used to extract lithium from lithium-rich aluminum electrolyte.In the first part,under the conventional conditions and ultrasonic assisted,the lithium-rich aluminum electrolyte was digested by acid leaching to realize the leaching of solid lithium resources,and the efficient leaching law of lithium-rich aluminum electrolyte was explored.Under conventional conditions,the optimal conditions for the digestion of lithium-rich aluminum electrolyte are acid concentration of 1 mol/L,reaction temperature at 75 ^oC,reaction time for 90 min,and liquid-solid ratio of 45:1(m L/g).The dissolution rate of the lithium-rich aluminum electrolyte is 86%,and the lithium dissolution rate is 76.48%.Under the action of ultrasonic wave,the optimal conditions for the digestion of lithium-rich aluminum electrolyte are acid concentration of 1 mol/L,reaction temperature at 75 ^oC,reaction time for 60 min,liquid-solid ratio of 1:45(m L/g),the dissolution rate of lithium-rich aluminum electrolyte is 88.56%,and the dissolution rate of lithium is 79.64%.The XRD patterns indicated that the digestion order of Na₃Al F₆,Na₅Al₃F₁₄,Li Na₂Al F₆ in lithium-rich aluminum electrolyte,from easy to difficult,is Na₃Al F₆,Na₅Al₃F₁₄,Li Na₂Al F₆.The quantitative correspondence between the dissolution rate of lithium-rich aluminum electrolyte and the lithium dissolution rate was established by regression analysis,and the lithium dissolution rate could be predicted semi-quantitatively in time,which was convenient for the industrialized extraction of lithium from the lithium-rich aluminum electrolyte.In the second part,the preparation of PVC-H_1.6Mn_1.6O₄membrane adsorbent and the characterization of its adsorption performance in Li⁺solution and lithium-rich aluminum electrolyte solution.The lithium ion-sieve precursor Li_1.6Mn1.₆O₄ was synthesized by hydrothermal method,and the PVC-Li_1.6Mn_1.6O₄ precursor membrane was prepared by using polyvinyl chloride(PVC)as the supporter.The Li⁺of the PVC-Li_1.6Mn_1.6O₄ precursor membrane was extracted by treating with HCl solution to obtain PVC-H_1.6Mn_1.6O₄membrane adsorbent.The SEM images and XRD patterns indicated that PVC-H_1.6Mn_1.6O₄ was successfully prepared.The time for PVC-H_1.6Mn_1.6O₄membrane to reach acid elution equilibrium and adsorption equilibrium was 480 min and 240 min,respectively.Under the premise of high mechanical strength and lithium adsorption capacity,the mass concentration of PVC was 12%,and the content of precursor Li_1.6Mn_1.6O₄ was 12%.In the Li⁺solution,the Li⁺adsorption capacity of PVC-H_1.6Mn_1.6O₄ membrane adsorbent was 680.89 mg/m².After 5 cycles of adsorption,the Li⁺adsorption capacity decreased by 5.75%.The selective adsorption experiment showed that the PVC-H_1.6Mn_1.6O₄ membrane adsorbent had good selectivity for Li⁺.The adsorption process of the PVC-H_1.6Mn_1.6O₄ membrane adsorbent conformed to the Langmuir isotherm adsorption model.In the lithium-rich aluminum electrolyte solution,the Li⁺adsorption capacity of PVC-H_1.6Mn_1.6O₄ membrane adsorbent was 381.82mg/m².After 5 cycles of adsorption,the Li⁺adsorption capacity reduced by 3.20%.The adsorption process of the PVC-H_1.6Mn_1.6O₄ membrane adsorbent also conformed to the Langmuir isotherm adsorption model.