Leaching behaviour of lithium, cesium and rubidium 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 tended to improve with increasing sulfuric acid concentration, especially in the range of 0.1 to 2 mol·dm-3, at the highest leaching temperature of 363 K. Further increase of the acid concentration to 4 mol·dm-3 H2SO4 appeared to have a limited improvement in their extent of leaching. Under the optimum conditions, 2 mol·dm-3 H2SO4 concentration and 363 K leaching temperature, the leaching ratios reached for lithium (Li), cesium (Cs) and rubidium (Rb) 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 exploited for the treatment of very high tonnages of clay containing processing waste of Kırka boron plant as potential Li (Cs and/or Rb) resource.