Leaching Of Lithium Rubidium Cesium From Lepidolite And Preparation Of Lithium Carbonate

Lepidolite has large reserves and high economic value,and is an important resource for extracting rare metals such as lithium,rubidium,cesium and their compounds.In this paper,the compound salt additive and lepidolite high-temperature roasting-leaching process are used.Based on the analysis of the raw material phase,roasting thermodynamics and mechanism analysis,the transformation law of lithium,rubidium and cesium in the roasting and leaching process is experimentally studied.The type and amount of roasting additives,the temperature,time,liquid-solid ratio and other conditions of the roasting and leaching process were systematically carried out,and the main influencing factors of the preparation of lithium carbonate from lepidolite leaching solution were studied.Environmental pollution and other issues and the purpose of efficient leaching of lithium,rubidium and cesium,the results are as follows:（1）The lepidolite mineral is a continuous layered tetrahedral structure with a complete crystal form,a flat crystal surface,and a jagged and irregularly distributed crystal edge.The minerals are composed of lepidolite,silica and albite,and lepidolite exists in the structure of K（Al,Fe,Li）（Si₃,Al）O₁₀（OH）F;（2）Combined with TG-DSC analysis,the calcination temperature range was determined to be 700～900℃,and the Gibbs free energy-temperature curve was drawn.On this basis,the roasting mechanism of compound salt is analyzed:calcium chloride mainly plays the role of decomposing lepidolite minerals and extracting rubidium and cesium,and sodium carbonate can derive lithium;XRD shows that anorthite and calcium silicate begin to appear at 700℃.Characteristic peak,at 800℃～900℃,the lepidolite and the compound salt fully react,which makes the lepidolite change from a dense and stable crystalline state to an inorganic salt.SEM shows that the lepidolite crystal is gradually corroded,forming agglomerates of irregular minerals Mutually;（3）Carry out roasting exploration experiments of different types’additives,and determine that the roasting additive is CaCl₂+Na₂CO₃.The optimal process conditions for the roasting-leaching experiment of lepidolite composite salt are:Lepidolite:CaCl₂:Na₂CO₃（mass ratio）=1:0.5:0.2,roasting temperature is 900℃,roasting time is 2h,leaching at room temperature,leaching time is 1h,liquid-solid ratio is 2:1,and the leaching rates of lithium,rubidium and cesium are:86.64%,92.58%,85.37%respectively;（4）The lepidolite leaching solution is purified to remove impurities and concentrate precipitated lithium to prepare lithium carbonate,thereby separating and enriching rubidium and cesium.The best process conditions for purification and impurity removal are:The purification temperature is room temperature,the purification reagent is 30%Na OH solution,the purification times are twice,and the filtration is performed at pH=8and pH>13,respectively,to remove most impurities,and then add an appropriate amount of 30%Na₂CO₃ solution is deeply decalcified to obtain a purification solution;the best process conditions for concentrating precipitation lithium are:Heating the concentrated purification solution to a lithium ion concentration of 14g/L,a precipitation temperature of 95℃,and a precipitation reagent of 30%Na₂CO₃ The solution,the dosage is 110%of the theoretical amount,the addition method is the reverse addition method,and the hot water is washed twice after filtration.The recovery rate of lithium carbonate can reach68.50%,the purity is close to 99.00%,and the crystallization is good,the size is uniform,the clear rod-shaped particles are,and the dispersibility is good.The recovery rates of rubidium and cesium are 72.78%and 63.51%,respectively.