Selective Extraction of Li, Rb, and Cs and Precipitation of Lithium Carbonate Directly from Lithium Porcelain Stone

Abstract

The expected increase in demand for alkali metal raises a concern over the difficulty in extracting Li, Rb, and Cs from hard rock ores. A four-step process is discussed to extract alkali metal from lithium porcelain stone. The process consists of roasting, leaching, evaporation and purification of lixivium, and precipitation of lithium salts. Two types of additives are used to enhance selective conversion into salts. The Li, Rb, Cs extraction efficiencies are determined to be 98.70, 97.27, 98.40%. An Na2SO4/CaCl2/ore mass ratio of 0.2/0.2/1 at 850°C for 60 min is used for the roasting step. Analysis of calcine and leach residue shows the cation ions from the reagents promote highly-chemo selective ion-exchange extraction of the alkali metals in the ores. After this process, the Li+ in lixivium is concentrated from 3.43 to 9.50 g/L by evaporation. A controlled amount of H2O2, NaOH, and Li3PO4 is added to the lixivium to remove the impurities. Precipitation of 94.09% of the Li in the purified solution by Na2CO3 is achieved. Further precipitation using Na3PO4 · 12H2O is done, leaving a solution from which Rb, Cs could be recovered. This proves the process is possible and practical.