| With rapid increase of demand for lithium resources,numeral researchers focus on the development and utilization of pegmatite lithium resources and brine lithium resources as well as the development and utilization of clay-type lithium resources.Because the current development and utilization for clay-type lithium resources had problems such as many impurity elements in leaching solution,hard to control the reaction,excessive acidity of the leaching solution and leaching residue,and environmental pollution etc.Therefore,this study is based on the idea of green-extraction,and on the premise of understanding of the mineralogical characteristics of clay-type lithium resources,employed roasting-salt leaching method,to achieve green,and efficient leaching of clay-type lithium resources.From the perspectives of main chemical composition,mineral composition,microscopic morphological,employed X-ray fluorescence spectroscopy,inductively coupled plasma emission spectroscopy,inductively coupled plasma mass spectrometry,powder crystal X-ray diffraction,scanning electron microscopy and other analytical techniques,to compare and analyze the difference of clay-type lithium resources between two samples（YM-1 and YM-2）of Yuxi,Yunnan province,and two samples（Ame-1 and Ame-2）of Nevada,the United States.The results showed that lithium’contents of clay-type lithium resources in Yuxi and Nevada are over 1000μg/g,which has certain value for development and utilization.However,there are significant differences in the main chemical composition,mineral composition,microscopic morphological and Li occurrence state of the clay-type lithium resources of two area.Specifically speaking:（1）The differences of main chemical composition:main composition of Yuxi two samples are similar with SiO2 and Al2O3（the total amount of silicon and aluminum oxides exceeds 80%）,while main composition of two samples from Nevada are SiO2 of Ame-1（60.39%）and CaO of Ame-2（42.30%）respectively.（2）The differences in mineral composition:mineral composition of Yuxi two samples are similar with kaolinite and montmorillonite,while mineral composition of two samples from Nevada are quartz,nontronite,stevensite of Ame-1 and calcite of Ame-2 respectively.（3）The differences in microscopic morphological:two samples from Yuxi（YM-1 and YM-2）are stacked by a layered structure with flat surfaces,round edges and relatively uniform size,while two samples from Nevada（Ame-1 and Ame-2）mainly represented by massive mineral aggregates of different sizes.（4）The differences of Li occurrence states:the lithium of two samples from Yuxi（YM-1 and YM-2）occurs in montmorillonite,while the lithium of two samples from Nevada（Ame-1 and Ame-2）occurs in the crystal lattice of smectite minerals or illite.This study used three common salt solutions of sulfate（ferric sulfate,ferrous sulfate,sodium sulfate）,chloride（ferric chloride,ferrous chloride,sodium chloride,calcium chloride）,and nitrate（ferric nitrate,sodium nitrate）as the leaching agent to extract the clay-type lithium resource samples.The results showed that compared to other salt solutions,ferric sulfate,ferric chloride and ferric nitrate have better selective leaching function of lithium ions in clay-type lithium resource samples.Due to the characteristics of less impurity elements in leaching solution of ferric sulfate,therefore,the iron sulfate leaching method was more conducive to the development and utilization of clay-type lithium resources.By batch experiments,using iron sulfate as the leaching agent,to investigate the impacts of roasting temperature,leaching agent concentration,leaching temperature,and leaching time on the leaching rate of lithium.The experimental results showed that the leaching rate of lithium was up to the highest（79.38%）when the roasting temperature was600℃,the mass fraction of ferric sulfate was 20%,the leaching temperature was 90℃,the leaching time was 180 min,and the rotating speed was 240 r/min.The analysis results of mineral composition and microscopic morphology of samples before the leaching of ferric sulfate solution and after leaching of the ferric sulfate solution at different temperatures showed that the mineral composition and lamella structure of samples after leaching at different temperatures are basically unchanged.Thus,the leaching of lithium was regarded as the result of ion exchange in this study.Additionally,by comparing the impurity content of the leachate,the acidity of the leachate and the acidity of the reaction residue leachate under the iron sulfate and sulfuric acid system,and compared with the sulfuric acid leaching method,the iron sulfate leaching method has advantages of low impurity content,weak acidity of the leaching solution,weak acidity of reaction residues,and green.The leachate of leaching of the iron sulfate solution as the research object,to make lithium carbonate by concentration-purification-concentration-carbonation.The results showed that purity（60.29%）of lithium carbonate can be obtained after process of concentration-purification-concentration-carbonation. |
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