助熔剂辅助碱熔-酸浸法制备高纯石墨

针对石墨中含有可溶性硅酸盐的情况,采用助熔剂辅助碱熔-酸浸法将天然鳞片石墨提纯,研究助熔剂种类及其用量、氢氧化钠质量分数、焙烧熔融温度、焙烧熔融时间对石墨纯化效果的影响,并对样品进行扫描电子显微镜(SEM)和X射线衍射(XRD)表征。结果表明:以偏硼酸锂作为碱熔焙烧助熔剂的纯化效果最佳。取质量分数60%的氢氧化钠溶液10 mL、质量分数20%的盐酸溶液20 mL、偏硼酸锂0.6 g、石墨10 g,在焙烧温度500℃、焙烧时间120 min、酸浸温度80℃、酸浸时间80 min的条件下,石墨的固定碳w(C)可由87.62%提高到99.69%。SEM和XRD分析表明,助熔剂辅助碱熔-酸浸法石墨纯化技术没有破坏石墨本身的结构与形貌。该工艺方法简单,反应温度低,污染小,能耗较低,能显著提高石墨的固定碳,可用于指导高纯石墨的生产实践。

Research on fluxing agent alkali fusion and acid leaching technology for graphite fabrication

This paper is devoted specifically to an effective response to the presence of soluble silicates in graphite. This response consists of using an auxiliary base flux melting-acid leaching method for purification of natural flake graphite, and defining the effect of the type and amount of flux, sodium content, melting temperature roasting, baking melting time on graphite purification, and characterizing sam- ple scanning electron microscope（SEM） and X-ray diffraction（XRD）. The study indicates that the lithi- um metaborate flux as alkali fusion roasting gives a best purification ; the presence of 10 mL of sodium hy- droxide solution with the mass fraction of 60%, 0.6 g of lithium metaborate, 10 g of graphite, calcination temperature of 500 ℃, roasting time of 120 rain, 20 mL of hydrochloric acid solution with the mass fraction of 20%, leaching temperature of 80 ℃, and acid immersion time of 80 rain allows fixed carbon graphite w（C） to be increased from 87.62% to 99.69%. SEM and XRD analysis suggests that the fluxassisted alkali fusion-acid leaching graphite purification technology eliminates damages to the structure and morphology. The process which features a simpler operation, lower reaction temperature, less pollution, and lower energy consumption allows a significant improvement in the content of fixed carbon graphite, demonstrating its potential as a guide to high purity graphite production.