Lithium recovery from boron production waste by high pressure-temperature leaching

The need for lithium is increasing day by day due to its widespread use in electric vehicles, hybrid motors, lithium-ion batteries of portable electronic devices, glass, ceramics, metallurgy, chemical production and nuclear industries. It is estimated that the need for lithium will more than double by 2025, especially with the production of electric vehicles. In order to meet the required demand, researches seem to focus on potential sources of lithium. For this purpose; it is seen that many studies have been carried out on the recovery of lithium from various minerals, lithium-containing brine, industrial wastes, waste batteries and electronic wastes. In our country having 72% of the world's boron reserves, it has been determined that the ores also contain lithium, which has an extremely high economic value, as well as high boron content.. It has been determined that lithium remains in production wastes after boron production. In this thesis; in order to recover the lithium in the boron production waste at a high rate, dissolution conditions with high temperature-pressure H2SO4 leaching were investigated instead of conventional leaching methods. For this purpose, the effects of temperature, contact time, acid concentration and liquid/solid ratio on leaching yield were investigated. In order to elucidate the leaching mechanism, the data obtained were applied to the heterogeneous leaching kinetics, some kinetic parameters were calculated and the steps limiting the solubility of lithium were identified. It was found that whole lithium in the waste was leached in the presence of 1 M H2SO4, and at the liquid/solid ratio of 10, 150˚C and 120 min contact time. Also, 261.5 mg/L calcium and 217.5 mg/L magnesium ions were detected in the solution along with lithium under these conditions. It has been determined that lithium leaching fits the decreasing shrinking core model of heterogeneous reaction kinetics and the rate is controlled by a mechanism which chemical reaction and ash film diffusion are effective together. The activation energy of the process was calculated as 34.16 kJ/mol. This value is in the range of activation energies given for diffusion-controlled and chemical-reaction-controlled systems, and is an indication that the system occurs with a mixed mechanism.