Selective Extraction of lithium from low-grade Gypsiferous Clays by reduction of Calcium and Magnesium content in the pregnant leach solution (PLS)

Abstract

Lithium extraction from all deposits is associated with magnesium and calcium ions as main impurities. In this study, an effective way provided to extract the maximum amount of lithium from clay deposits while minimizing extraction of magnesium and calcium ions. After pre-feasibility studies on extraction methods, the limestone-gypsum roasting with water-leaching technique was selected for final studies. After identifying effective parameters including furnace temperature, roasting time, the ratio of calcium carbonate to feed and the ratio of calcium sulfate to feed, Taguchi experimental design was used to optimize experimental conditions and variables. For this purpose, DX7 software and L25 array were used. A furnace temperature of 800 ° C, roasting time of 2 h, a calcium carbonate to feed ratio of 1:5 and a calcium sulfate to feed ratio of 4:5 were obtained as the optimal technical and economic conditions with a lithium recovery of 68.7%. The highest lithium recovery of 75.65% was obtained at a furnace temperature of 1100 ° C, roasting time of 5 h, a calcium carbonate to feed ratio of 1:5 and a calcium sulfate to feed ratio of 1:5. In both cases, magnesium was completely removed and the maximum content of calcium (in optimal technical and economic conditions) in the leach solution was 0.1%