Characterization and treatment of clayey waste using a sulfuric acid roasting-water leaching process for the extraction of lithium

Abstract

In this study, a detailed characterization of the clayey waste of the Kırka boron plant was undertaken before the development of a sulfuric acid roasting-water leaching process for the extraction of lithium from this waste. The effects of roasting temperature (650-800°C) and sulfuric acid/waste ratio (90-260 kg H2SO4/1000 kg waste on a dry basis) on the extraction of lithium were investigated. By roasting the waste sample, which contained 0.37% Li2O with dolomite, smectite and borax as the main phases, at temperatures between 650°C and 800°C in the absence of sulfuric acid as the additive, CaMgSiO4 was found to form as the dominant phase after the decomposition of dolomite and smectite present in the sample. On the other hand, the X-ray diffraction analyses of the waste sample subjected to sulfuric acid treatment without roasting showed the in-situ formation of various hydrated calcium sulfate phases for all sulfuric acid/waste ratios tested. Besides, at the highest acid/waste ratio of 260, a hydrated magnesium sulfate phase was also identified in the sample. The application of the sulfuric acid roasting-water leaching process under the optimum roasting temperature of 750°C and the acid/waste ratio of 180 was found to lead to a lithium extraction of 85.7%. The applied sulfuric acid roasting-water leaching process appeared to be an attractive process with its attributes including low roasting temperature, high extraction percentage and no requirement for gypsum as the external sulfation agent