Investigation of lithium leaching from boron production waste and its thermally activated products

In this thesis, it was investigated the lithium leaching from boron production waste and its thermally activated products. For this purpose, effects of leach reagent type (water, sulfuric (H2SO4), nitric (HNO3), oxalic (C2H2O4), tartaric (C4H6O6), citric (C6H8O7), ascorbic (C6H8O6) acids and sodium hydroxide (NaOH)) and concentration, contact time, temperature and liquid/solid ratio on the lithium leaching were investigated, while only effects of contact time and temperature on the leaching of lithium from the thermally activated products by water leaching were investigated. Optimum leaching conditions were determined for each leaching. Additionally, leaching solutions were analyzed and recoverability of the lithium in the form of lithium carbonate (Li2CO3) was also examined. In order to determine the leaching mechanism, the data obtained were applied to heterogeneous reaction kinetics and the steps limiting lithium leaching were revealed. It was found that the leaching rates with water, NaOH, and C6H8O6 were quite low (3.7%, 9%, and 25%, respectively), 100% of leaching rates could be achieved with H2SO4 (0.5 M, 50C, 120 min), HNO3 (1.0 M, 50C, 90 min) and C2H2O4 (0.5 M, 75C, 60 min) and, 93% and 76% leaching rates could be obtained in the presence of C4H6O6 (1.0 M, 75C, 120 min) and C6H8O7 (1.5 M, 75C, 120 min), respectively. Compared to lithium, it has been determined that the main waste structure consist of impurities, thus lithium leaching kinetics fit to the shrinking core model, and leachings are generally controlled by a dual mechanism consisting of ash film diffusion and chemical reaction. Keywords: Lithium, Leaching, Extraction, Thermal activation, Recovery