Study On The Preparation Of Lithium Carbonate From Medium To Low Grade Lithium Porcelain Stone By Composite Sulfate Method

With the rapid development of new energy sources,the demand for lithium has increased significantly.In this paper,using medium and low grade lithium porcelain stone（Li₂O=1.86%）and high grade lithium mica（Li₂O=4.0%）as raw materials,the sulfuric acid roasting salt method and the chloride roasting method were used to extract lithium from lithium ores,respectively.The first part:Using sodium sulfate,potassium sulfate,calcium sulfate,and other sulfates as roasting aids,the roasting water leaching method was used to extract lithium from lithium ores.The effects of factors such as sulfate type,ore material ratio,roasting temperature,and roasting time on the lithium ion leaching rate were discussed,and the thermodynamics,microscopic morphology,and phase changes during the roasting process were studied.The results show that:The optimal roasting conditions for the lithium ceramic stone composite sulfate roasting method are as follows:roasting temperature 850℃,roasting time 1 h,lithium ceramic stone potassium sulfate sodium sulfate=1?0.35?0.15.The optimal leaching conditions are:L/S（volume mass ratio,L/g）=2,leaching temperature 95℃,leaching time 1h.The best conditions for lithium precipitation are:precipitation temperature95℃,precipitation time 2h,adding 1.2 times the theoretical amount of 30%sodium carbonate solution.Under these conditions,after roasting 500 g of lithium ceramic stone,the lithium ion leaching rate reaches 95%.10.4 g of lithium carbonate was obtained by primary precipitation of the leaching solution with a purity of 99%.After cooling and salt precipitation,4.5 g of lithium carbonate was obtained by secondary precipitation of the filtrate with a purity of 92%.The overall yield of lithium was 63.1%.During the calcination process of lepidolite,at 700℃,lepidolite begins to transform into KAl Si₃O₈ phase,and as the temperature increases,it then transforms into KAl Si₂O₆ phase and Si O₂ phase.Finally,it exists in the residue in the form of KAl Si₂O₆,Si O₂,and KAl Si₃O₈,thereby preventing aluminum ions from entering the leaching solution during the impregnation process.The optimal roasting conditions for the lithium mica composite sulfate roasting method are:roasting temperature 850℃,roasting time 1 h,lithium mica,sodium sulfate,calcium sulfate=1?0.3?0.7.Under these conditions,after roasting 500 g of lepidolite,the leaching rate of lithium is 87%.31.9 g of lithium carbonate was obtained by primary precipitation,with a purity of 99.3%.After cooling and salt precipitation,1.9 g of lithium carbonate was obtained by secondary precipitation of the filtrate,with a purity of 94%.The overall yield of lithium was 67.7%.At high temperatures,lepidolite mainly transforms into KAl Si₂O₆,Ca Al₂Si₂O₈,KLi SO₄,and Na Al Si₃O₈.The second part:Using sodium chloride and calcium chloride as roasting aids,the roasting water leaching method was used to extract lithium from lithium ores.The effects of factors such as chloride salt type,ore material ratio,roasting temperature,and roasting time on the leaching rates of lithium,rubidium,and cesium were discussed.The thermodynamics,microscopic morphology,and phase changes during the roasting process were studied.The results show that:The optimal roasting conditions for the lithium ore complex chloride salt roasting method are:roasting temperature 850℃,roasting time 1 h,lithium ore sodium chloride calcium chloride=1?0.2?0.3.Under these conditions,after calcination and water leaching of lithium porcelain stone,the leaching rates of lithium,rubidium,and cesium are 92.1%,90.4%,and 92.7%,respectively.After roasting 500 g of lithium ceramic stone,the lithium leaching rate is 85.6%,the purity of the final lithium carbonate product is 98%,and the overall yield of lithium oxide is 39.8%;The leaching rates of lithium,rubidium,and cesium from lepidolite after calcination with complex chloride salts and water leaching are 94.3%,92.6%,and 93.5%,respectively.After roasting 500g of lepidolite,the lithium leaching rate is 87.3%,the purity of the final lithium carbonate product is 99.2%,and the overall yield of lithium oxide is 63.1%.The surface of lithium ore after roasting with complex chloride salts is no longer smooth and smooth.Through XRD patterns,it is found that lithium ore and calcium chloride sodium chloride mainly form substances such as KCl,Na Al Si₃O₈,Ca F₂,Si O₂,Ca Al₂Si₂O₈,etc.after high-temperature roasting.