Study On Leaching Process Of Lithium From Lepidolite Through Mechanochemical Activation Treatment

With the rapid development of new energy vehicles,the demand of lithium-ion batteries has grown rapidly,leading to rapid market demand for lithium and its compounds.At present,extraction from minerals is the main method for the production of lithium and its compounds.So it is particularly critical to establish a high-efficiency and green technology to extract lithium(Li)and its compounds from lepidolite.Given the special mineralogical nature and stable phase structure of lepidolite,the current method,such as,sulfuric acid leaching and limestone calcination,usually have long technologies and low extraction efficiency of Li.Meanwhile,a large amount of acidic wastewater and waste residue are also generated in the process.So it is particularly critical to establish a high-efficiency and green technology to extract lithium(Li)and its compounds from lepidolite.In view of this situation,this paper systematically characterized and analyzed the lepidolite,introduced a mechanochemical activation method to enhance the extraction of Li,and systematically studied the relevant process parameters of the mechanochemical process and leaching process.Besides,the reaction mechanism of the process was also discussed.Finally,efficient lithium extraction from lepidolite was achieved through intensifying the in-situ conversion of raw material phase.The main research content is as follows:(1)Energy dispersive spectrometer(EDS),scanning electron microscope(SEM),inductive Coupled Plasma Emission Spectrometer(ICP),and Mineral Liberation Analysis(MLA)were used to characteristic the lepidolite.The analysis showed that the lepidolite concentrate is mainly composed of three types of ore phases:lepidolite,quartz and albite.The main components of them is silica and alumina with 1.46%rare and precious metal.Besides,it contains highly toxic element fluorine.In the lithium mica,the particles below 200 um are about 98.53%,and the content of' 74 um is 69.75%.The number of particles containing lepidolite was 46.75%,of which 72.6%of the lepidolite particles were completely dissociated,and the remaining particles were mainly associated with sodium Abite,Quartz and Muscovite.(2)Mechanochemical method to enhance the extraction process was systematically performed,and the optimal conditions were obtained.The leaching efficiency of Li was 99.1%from lepidolite,which had been treated by ball-milling with potassium salt at lepidolite and potassium salt ratio of 5:1,ball to powder weight ratio of 20:1,500 rpm and 3h.The mechanism of mechanochemical process of lepidolite was described by analyzing the change of phase and morphology before and after ball-milling.(3)The leaching of Li from lepidolite by sulfuric acid was studied systematically,and the optimal conditions were obtained.The leaching efficiency of Li was 99.1%under the conditions of 15%(v/v)sulfuric acid at 200rpm,4 L/kg,and 80?.Meanwhile,the characterization of the mineral before and after leaching showed that the lithium-containing phase had disappeared,which indicated that the lithium was completely leached out.In addition,high-purity lithium carbonate was also obtained from leachate.Potassium sulfate was recovered and reused through concentration and crystallization.In the summary,a sustainable green process route was established to achieve lithium extraction from lepidolite.