微晶石墨除杂脱硅研究

Experiment & ResearchStudy on Removing of Silica Impurity from Microcrystalline Graphite

针对微晶石墨中硅杂质难脱除的特点 ,进行了高温碱法结合氢氟酸法除硅的研究 ,发现氢氟酸和氢氧化钠加入量对提纯效果的影响最为显著 ,它与焙烧时间、焙烧温度和酸浸时间一起对石墨的提纯效果有显著影响。在合适工艺条件下 ,可得到固定碳C含量≥ 99 5 %的高纯石墨产品。焙烧样品水洗干净与否直接影响样品的最终固定碳含量 ,硅杂质脱除效果不佳的重要原因 ,是高温碱处理后残留的钠离子与待处理的铝、硅杂质离子反应 ,生成不溶性的冰晶石 [Na3AlF6

According to the difficulty in removing silicic impurity for microcrystalline graphite, research of purification through alkali roasting binding with hydrofluoric acid was carried out. The amount of hydrofluoric acid and alkali contribute most to the effect of purification. Temperature and time of alkali roasting and acid leaching were all found the prominent factors to the effect of purification at the same time. In this experiment, a effectual way to get rid of the silicic impurity in graphite was found, which help us to get a graphite product with a carbon content over 99.5%.The sample had been cleaned from washing process is the efficient fact,by which super pure graphite can be got .In this paper, conclusion was drew that the rudimental natrium ion from alkali leaching process can be deposited with the silicic and aluminous ion during the acid washing process to transform into cryolite[Na 3AlF 6] and fluoric sodium.