滕南煤田煤矸石锂镓赋存及柠檬酸选择性浸出研究

Study on the Occurrence of Lithium Gallium and Selective Leaching of Citric Acid in Coal Gangue of Tengnan Coalfield

  • 摘要: 锂镓是重要战略性关键金属,煤矸石中赋存的锂镓具有低开采成本、储量丰富等特点,是一种重要的二次资源。因此,查明煤矸石中锂镓的赋存状态,开发其绿色高效提取技术,已成为该领域面临的关键挑战。本论文以滕南煤田煤矸石为研究对象,利用逐级化学提取和物理分选方法研究锂镓的赋存特征,结果表明煤矸石中锂镓元素主要以残渣态(铝硅酸盐态)赋存,占比超过90%,锂镓主要分布在2.4~2.6 g/cm3密度级产物中,其中锂的富集倍数达到1.25,各煤矸石指标基本一致。煤矸石经600 ℃焙烧2h活化后,采用1 mol/L柠檬酸浸出锂镓,结果显示锂元素的浸出率达到了75.01%,镓的浸出率为36.15%,而常量元素浸出率分别为铝16.49%、铁11.19%、钛3.99%,均远低于锂镓。扫描电镜−能谱(SEM−EDS)与红外光谱(FT−IR)分析结果证明,在不破坏铝硅酸盐中Al−O键的前提下,通过柠檬酸三级电离逐步释放氢离子,保证锂镓的溶出的,同时柠檬酸根离子发生锂镓离子配位反应而结合,减少溶液中锂镓离子,促进固相中锂镓的进一步溶出,实现了锂镓选择性浸出。本研究系统地分析了滕南煤田煤矸石中锂镓的资源禀赋,提出了利用方法,可为该地区煤矸石高值化利用理论支撑。

     

    Abstract: Lithium and gallium are important strategic key metals. Coal gangue, of which lithium and gallium has the characteristics of low mining cost and abundant reserves, is regarded as an important secondary resource. Therefore, identifying the occurrence state and developing green and efficient extraction technologies of lithium and gallium in coal gangue have become key challenges in this field. This paper collected coal gangue of Tengnan Coalfield as the research object and studied the occurrence characteristics of lithium and gallium using sequential chemical extraction and physical separation methods. The results show that lithium and gallium in coal gangue mainly exist in the residual state (aluminosilicate state), accounting for more than 90%. Lithium and gallium are mainly distributed in coal gangue with a density range of 2.4 to 2.6 g/cm3, in which the enrichment factor of lithium reaches 1.25. After being calcined at 600 ℃ for 2h, coal gangue was leached with 1 mol/L citric acid for the extraction lithium and gallium. The results show that the leaching rate of lithium reached 75.01%, along with 36.15% for gallium, while that of untargeted elements were 16.49% for aluminum, 11.19% for iron, and 3.99% for titanium. The analysis results of scanning electron microscopy−energy dispersive spectroscopy (SEM−EDS) and fourier transform infrared spectrometer (FT−IR) prove that the hydrogen ions ionized by citric acid during the leaching process could not break the Al−O bond in the aluminosilicate structure. Citric acid generates hydrogen ion and citrated through three−stage ionization, resulting in lithium and gallium selective extraction by continuous acidification and coordination. This paper systematically is supposed to provide theoretical support for the high−value utilization of coal gangue in Tengnan Coalfield through the revelation of lithium and gallium characteristic and extraction assessment.

     

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