关键词: 富钾正长岩, 水热, 化学反应, 硫酸钾, 硅灰石, 高岭土, 绿色加工

Abstract: To develop an efficient and clean technique for comprehensively utilizing potassic syenite resources exposed in the Eastern Qinling to Dabie area of China, a series of experiments were performed using a typical K-feldspar powder as raw material, with focus on the hydrothermal stability of microcline in KOH-H₂O solution, reaction principle of preparing potassium sulfate, as well as processing by-products from alumina and silica residue. Microcline was easily transformed into kalsilite by dislodging 2/3 SiO₂ of the K-feldspar in the solution, resulting in nearly hundred percent higher concentration of K₂O in the solid product, from which nearly pure solution of potassium sulfate was then obtained by dissolution with sulfuric acid, and further potassium sulfate was crystallized by evaporation of the solution or by the alcohol precipitation method. The alkaline solution of mainly potassium silicate reacted with lime milk to precipitate calcium silicate hydrate, from which needle-shaped wollastonite powder was synthesized hydrothermally, and then by calcination. The alumina and silica residue were used to make calcined kaolin first by acidic washing, and then by calcination. The whole procedure developed in this research was simple and economical, with recovery ratio of K₂O up to 94.0%. In such a way, the components of K₂O, Al₂O₃, and SiO₂ in K-feldspar of the ores were wholly transformed to valuable products, giving rise to maximum utilization of K-feldspar resources, and also minimum consumption of relevant mineral resources. The technique is noted for energy conservation, high efficiency and clean production.

Key words: potassic syenite, hydrothermal, chemical reaction, potassium sulfate, wollastonite, kaolin, green processing