Production of Potassium Chloride from K-Feldspar Through Roast-Leach-Solvent Extraction Route

Abstract

This work focuses on extraction of potassium from feldspar through pyro-hydrometallurgical route. Calcium chloride was used as roasting agent for feldspar. Effect of various operating variables, viz. time, roasting temperature and CaCl2 dose on extent of roasting, were thoroughly studied. Roasting 10 g of feldspar with 17 g of CaCl2 at 900 degrees C for 1 h resulted in 99.9% conversion of K2O to KCl. Order of feldspar roasting was found to be around 2, and activation energy requirement was 136.6 kJ/mol. Calcium and sodium were leached along with potassium from chloride-roasted K-Feldspar with water at room temperature. To generate a pure solution of potassium from the leach liquor containing K, Ca and Na, it was selectively extracted from leach liquor by using dibenzo-18-crown-6 ether as extractant and m-cresol as diluent. Loading of potassium was carried out at an A/O ratio of 2:1, while stripping was carried out in water at O/A ratio of 2:1. 99.5% pure crystals of KCl were obtained on evaporation of the strip solution. A schematic flowsheet has been provided for the preparation of pure KCl from feldspar.