Lepidolite Extraction Of Lithium From A Clean Slag Preparation Of Aluminum Sulfate

For make qualified lithium carbonate from lifted lithium-leach liquor of lepidolite in sulfate, have to remove impurity step by step on leach liquor. First purification residue is production after formed hydroxide precipitates of Al3+ in leach liquor, by adjusting the pH of leach liquor by using CaO. This result is″residue″highly of first purification residue which is very high in Al and Ca, If the residue is discharged or piled up directly, it would be cause wasteful of resource and pollution of environment. Therefore, recovering the resource of aluminium and calcium in first purification residue is referenced, which not only reduces the environmental pollution but also has some economic value.This thesis recovers aluminium and calcium of purification residue by sulfuric acid leaching. Preparation main product of aluminum sulfate by abstracting aluminium, and calcium sulfate by precipitating calcium which return to main process flow of producing lithium carbonate for circulation utilization. For making a qualified product of aluminum sulfate, settling purification residue in advance is selected by means of roasting and water extraction which based on the phase characteristics and content of purification residue, the aim of that is leaching element of the alkali metal in purification residue. The factors that influenced leaching rate of element of the alkali metal are investigated during water extraction, including roasting temperature, roasting time, temperature, liquid-solid ratio and time of water extraction etc. Under the optimum conditions, leaching rate of lithium, sodium potassium, rubidium and cesium reaches 82.30%, 79.68%, 83.95%, 86.86% and 81.23% respectively.Purification residue after removing element of the alkali metal by roasting and water extraction is renamed aluminium-calcium residue. The relationship between leaching rate and factors is studied, which include the amount of sulfuric acid(32～34%), the temperature and time of acid extraction, liquid-solid ratio, stirring intensity etc in the process of single stage leaching aluminium-calcium residue by sulfuric acid. The results indicated that the concentration of aluminium sulphate solution is low in the optimum conditions which single stage extraction aluminium-calcium residue by sulfuric acid, and free acid content is higher in aluminium sulphate solution, that needs to use up a large number of alkali for counteracting and cost are enlarged.On the basis of the problems present in the single stage extraction, three stage upstream leaching is used instead. Adjusting technology parameters based on the single stage leaching to get appropriate conditions, in these conditions, the leaching rate of aluminium is as high as 98% which has a rise of 2% compared with single stage leaching, and the concentration of aluminium sulphate solution is raised substantially. Settlement of aluminium sulphate solution in the second and third stage is the major problem in the process of three stage upstream leaching. Influence of the concentration and amount of flocculant on settlement is studied when non-ionic polyacrylamide is selected for flocculant, and the best concentration and amount of flocculant are fixed.Finally, aluminium sulphate solution that have collected is used to evaporate, output voltage is controlled in this progress, removed from the heat when the white powder aluminium sulphate appeared in the bottom of the flask, the production of aluminium sulphate is obtained after being cooling naturally. The prepared aluminium sulphate measures up to the quality standard of grade-1 of the technical aluminium sulphate through detecting and analysis.