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

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 (5.5 wt.%) and kalsilite at a mass ratio of 6.26 and a temperature of 60 °C for 4 h. 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 168 mg CaO/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.