Studies on Extraction of Potassium from Feldspar by Roast-leach Method Using Phosphogypsum and Sodium Chloride

The extractions of potassium value from feldspar via roasting and leaching route was studied with a focus on the effects of the roasting time, temperature, additives, and particle size. Sodium chloride and phosphogypsum (PG) were used as a source of chloride and calcium, respectively, and played the important role during the roasting of feldspar. When the feldspar sample was roasted at 900°C with sodium chloride alone, the extraction of potassium was limited to 61%. The extraction could go up to 92.5% by the addition of phosphogypsum along with sodium chloride. The optimum conditions of potassium extraction were found to be, particle size 100 µm, roasting temperature 900°C and roasting time of one hour. The X-ray diffraction study indicated the formation of sylvite (KCl) in the roasted product and its disappearance in roast-leach residue due to its high water solubility. The morphological changes during the roasting process were clearly observed by field emission scanning electron microscope (FESEM) images. The extraction of potassium from feldspar was best fitted by the Ginstling and Brounshtein kinetic model. The activation energy of 238.6 KJ/mole and 28.73 KJ/mole for low and high-temperature regions indicated that the overall extraction process follows two-steps reaction path.