Insights into Alkali-Acid Leaching of Sericite: Dissolution Behavior and Mechanism

Sericite is a typical silicate impurity in microcrystalline graphite ores, and its removal is important in the preparation of high-purity graphite preparations. Alkali-acid leaching is an effective method used to purify graphite and remove silicate minerals. In this study, the dissolution behavior and mechanism of sericite in alkali-acid leaching were investigated. The dissolution of sericite was mainly affected by alkali leaching temperature, sodium hydroxide concentration, and alkali leaching time. According to the XRD, FTIR, and SEM-EDS analyses, the dissolution mechanism of sericite is a three-stage process: (1) sericite is dissolved in the form of soluble silicate and aluminate; (2) the dissolved silicate and aluminate then react with each other to form aluminosilicate; and (3) finally the aluminosilicate mainly composed of hydroxycancrinite and sodalite is almost completely dissolved in the hydrochloric acid solution.