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随着新能源汽车领域的快速发展，锂离子电池作为其主要动力来源，需求量急剧增长，导致市场对于锂及其化合物的需求快速增长。现阶段国内生产锂及其化合物的主要方式还是从矿物中提取。因而，如何建立一种高效绿色的从矿物中提锂的方法显得尤为关键。从锂云母中提取锂主要采用硫酸法和石灰石煅烧法等方法，但是由于锂云母特殊的矿物学性质和稳定的物相结构，导致锂云母处理工艺流程长、酸用量大，且提取率相对较低，过程中还产生大量的废渣和酸性废水。针对这一现状，本文对所收集到的锂云母进行了系统的矿物学表征和分析，引入了机械化学活化方法强化提锂过程，系统地对提锂工艺的相关工艺参数进行了研究，对相关过程的反应机理进行了讨论探究。最终，通过强化含锂物相的原位转化实现从锂云母中高效提锂。主要研究内容如下：（1）借助SEM，EDS，ICP，XRF以及MLA等表征技术，系统地对锂云母矿进行了矿物学分析表征。分析表明，锂云母精矿主要是由锂云母、石英、钠长石、白云母三种矿相组成。主要成分为二氧化硅和氧化铝，含有2.92%的稀贵金属锂，同时含有腐蚀性剧毒元素氟元素。锂云母中200μm以下颗粒约占98.53%，74μm粒级含量占69.75%。含锂云母的颗粒数占比46.75%，其中72.6%的锂云母颗粒完全解离，其余颗粒主要与钠长石，石英，白云母伴生。（2）系统地开展了机械化学活化锂云母强化过程的实验，得到了最佳工艺。最佳机械化学活化参数为采用钾盐作为活化剂，控制转速500 rpm，精矿与活化剂比例为5:1，球磨时间3 h，球料比为20:1。通过对活化前后的物相，形貌变化分析，对钾盐活化锂云母过程进行了阐述。（3）针对活化后的浸出过程，系统地开展了活化后锂云母的浸出实验，得出了最佳的浸出工艺条件。在硫酸体积分数为15%（v/v），液固比为4:1 (L/kg)，搅拌速率200 rpm，反应温度80℃条件下进行浸出，锂的浸出率可高达99.1%。同时，通过对锂云母浸出前后的物料进行物相的表征对比亦发现含锂物相已经消失，表明锂被完全浸出。此外，对浸出液中的锂进行了除杂，提纯，制备得到高纯碳酸锂，并通过浓缩结晶，实现了硫酸钾的回收再利用，建立了一条可持续的绿色工艺路线。;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. 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 shown 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 0.68% 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 Albite, Quartz and Muscovite.(2) Mechanochemical method to enhance the extraction process was systematically performed, and the optimal conditions was 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 was 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 oC. Meanwhile, the characterization of the mineral before and after leaching shown 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.
|何明明. 锂云母机械化学活化提锂工艺研究[D]. 中国科学院研究生院,2018.|
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