Preparation of potassium sulfate and zeolite NaA from K-feldspar by a novel hydrothermal process

• Published in: International journal of mineral processing Vol. 155; pp. 130 - 135
• Main Authors: Su, Shuangqing, Ma, Hongwen, Chuan, Xiuyun, Cai, Biya
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.10.2016
• Subjects: Construction; Evaporation; Hydrothermal process; K-feldspar; Mineral processing; Ores; Potassium; Potassium sulfate; Residues; Sulfates; Zeolite NaA; Zeolites; Hydrothermal process; Zeolite NaA; Potassium sulfate; K-feldspar
• ISSN: 0301-7516; 1879-3525
• DOI: 10.1016/j.minpro.2016.08.017

This paper describes a novel hydrothermal method for preparing potassium sulfate and zeolite NaA from K-feldspar ore. The 3-step process involves the hydrothermal decomposition of K-feldspar, the preparation of potassium sulfate from kalsilite, and the synthesis of zeolite NaA from alumina-silica residue. K-feldspar transformed into kalsilite in a KOH solution at 280°C. K2O was extracted from kalsilite at a rate of 95.73% by using H2SO4 (5.5wt.%) and kalsilite at a mass ratio of 6.26 and a temperature of 60°C for 4h. Subsequently, agricultural-grade potassium sulfate was crystallized by direct evaporation of the resulting K2SO4 solution. The CEC value of zeolite NaA produced from the alumina-silica residue was 168mgCaO/g, making it a suitable substitute for conventional phosphatic washing builders. The method is a simple, clean and energy-efficient method for the utilization of K-feldspar ores. •A comprehensive use of K-feldspar to prepare potassium sulfate and zeolite NaA by a novel hydrothermal process is proposed.•The K-feldspar powder transformed into kalsilite in KOH solution at 280°C.•Nearly pure K2SO4 solution was prepared by dissolving kalsilite with sulphuric acid, and agricultural-grade K2SO4 product was crystallized by direct evaporation of the resulting K2SO4 solution•Zeolite NaA was synthesized by crystallizing the alumina-silica residue in 3M NaOH solution.