Thermal treatment of K-feldspar for potassium recovery using NaCl–CaCl2 mixture and its mechanism study

Abstract

Abstract The increasing global demand for potassic fertilizer, due to the population growth, indirectly forces many countries to search for an alternative source of potassium. The present study reports the recovery of potassium from K-feldspar (K2O 12.5 wt. %) through the chlorination roasting—water leaching process applying a mixture of CaCl2 and NaCl. Individual use of NaCl and CaCl2 results in the extraction of ∼50% and 92% of potassium, respectively. Though the K-extraction is very high via CaCl2 roasting process, it adds an extra cost to the process as compared with NaCl. However, the use of salt mixture CaCl2: NaCl (40:60 wt. %) recovers potassium to the tune of ∼98% at optimum conditions (850 °C, 60 min roasting period, salt mixture: feldspar 1:1). Various experimental parameters such as temperature, time, and salt to feldspar ratio were optimized to recover maximum potassium from the complex structure of K-feldspar. The experimental results are explained using a theoretical extraction model, further supported by characterizations of the samples using XRD, SEM-EDX and FTIR studies. NOVELTY STATEMENTS Potassium extracted from K-feldspar applying a mixture of CaCl2 and NaCl. The chlorination-roasting temperature (using salt mixture) was lesser (by 50 °C) as compared with the use of individual salts. The extraction process (using salt mixture) was less expensive as compared with the use of independent salts. The K-extraction mechanism has been discussed considering the experimental results. Characterization studies support the proposed extraction mechanism.