A typical flake graphite concentrate sampled from a graphite flotation plant was used to prepare high purity graphite. The carbon content of the concentrate was 85.6%, and silicate and iron-containing minerals were found principally in the concentrate. High-grade graphite concentrate with a carbon content of 95% was obtained in the flotation process with feed pulp of 5% solids by weight after regrinding by a low-speed ball milling system. A small amount of the flotation reagents such as caustic soda, water glass, kerosene, and pine oil were added. The resulting flotation concentrate was mixed with alkali and roasted at 500 °C for 90 min. During the alkali roasting, the silicate mineral was converted into the water- and acid-soluble materials. Afterward, the soluble materials and iron-containing minerals were dissolved by acid leaching. As a result, a product with a carbon content of 99.82% was prepared. According to the calculation results of Gibbs energy, the reactions between impurities and chemicals in alkali roasting and acid leaching processes were spontaneous. The purification route was very effective for high purity graphite production and has been successfully applied in the pilot-scale experiment.

从石墨浮选厂取样的典型片状石墨精矿用于制备高纯度石墨。精矿含碳量为85.6%，精矿中主要发现硅酸盐和含铁矿物。以固体重量为5%的进料矿浆经低速球磨系统重磨后浮选得到含碳量95%的高品位石墨精矿。加入少量烧碱、水玻璃、煤油、松油等浮选药剂。将所得浮选精矿与碱混合并在 500°C 下焙烧 90 分钟。在碱焙烧过程中，硅酸盐矿物转化为水溶性和酸溶性物质。之后，可溶性物质和含铁矿物通过酸浸溶解。因此，制备出含碳量为99.82%的产品。根据吉布斯能量计算结果，碱焙酸浸过程中杂质与化学物质的反应是自发的。该提纯路线对高纯石墨生产非常有效，并已成功应用于中试。