Leaching behaviour of lithium from a clay sample of Kırka borate deposit in sulfuric acid solutions

Abstract

In this study, the leaching behaviour of lithium, together with cesium and rubidium, from a clay sample of Kırka borate deposit in sulfuric acid solutions was investigated with chemical, XRD, FTIR, DTA analyses methods and specific surface area measurements. It was observed that the leaching behaviours of lithium, cesium and rubidium were quite similar in character in that their extent of leaching, and their leaching markedly increased with the increase of sulfuric acid concentration from 0.1 to 2 M at 90°C. Further increase in the concentration of sulfuric acid to 4 M appeared to have a limited improvement on their leaching ratios. In 2 M H2SO4 solution and at 90°C, the optimum conditions, the leaching ratio values obtained for lithium, cesium and rubidium were 97.2, 83.7 and 65.2%, respectively. The results of XRD, FTIR and DTA analyses applied to the clay sample and the leaching residue obtained after leaching of the clay sample under the optimum conditions collectively showed that almost complete destruction of crystalline smectite structure(s) in the clay sample caused by acid leaching resulted in the formation of amorphous silica phase in the leaching residue. During this transformation, as expected, the specific surface area of the clay sample increased, from 59 to 406 m2/g. The results obtained in this preliminary study may be used in hydrometallurgical treatment of very high tonnages of clay containing processing waste of the Kırka boron plant as a potential lithium (cesium and/or rubidium) resource in the future.