Competency of chlorination roasting coupled water leaching process for potash recovery from K-feldspar: Mechanism and kinetics aspects

Abstract

Potassium is an important mineral for biological functions. In this study, potassium was recovered from a low-grade potash mineral, feldspar through chlorination roasting followed by water leaching. NaCl and CaCl2 were used as additives for chlorination roasting independently. The characterizations throughout the studies were carried out using a series of analytical and spectral techniques like XRD, SEM, FTIR, and Raman spectroscopy. The effects of various experimental parameters such as particle size, roasting temperature, amounts of additives, and water leaching on potassium extraction were evaluated. Water leaching was found to be independent of leaching time, temperature, and agitator speed. During roasting, the formation of water-soluble phase was evident; this phase subsequently disappeared on water leaching. The potassium extraction kinetics in the presence of both the additives was satisfactorily corroborated by Ginstling-Brounshtein model. The activation energies for CaCl2 and NaCl roasting were calculated to be 90 and 122 kJ/mole, respectively. Under the same experimental conditions, 86% of potassium extraction (as potash value) was accomplished using CaCl2 as the additive, whereas the extraction in presence of NaCl was only up to 44%. The mechanism of potassium extraction was elucidated; the superior effectiveness of CaCl2 over NaCl in the extraction process was also explained.