Kinetics of leaching lithium from lepidolite using mixture of hydrofluoric and sulfuric acid

Abstract

The fluorine-based chemical method shows great potential in leaching lithium (Li) from lepidolite. Leaching kinetics of Li in a mixture of sulfuric acid and hydrofluoric acid, which is a typical lixivant for the fluorine-based chemical method, was carried out under crucial factors such as different HF/ore ratios (1:1–3:1 g/mL) and leaching temperatures (50–85 °C). The kinetics data fit well with the developed shrinking-core model, indicating that the leaching rate of Li was controlled by the chemical reaction and inner diffusion at the beginning of leaching (0–30 min) as a calculated apparent activation energy (Ea) of 20.62 kJ/mol. The inner diffusion became the rate-limiting step as the leaching continues (60–180 min). Moreover, effects of HF/ore ratio and leaching temperature on selective leaching behavior of Li, Al and Si were discussed. 90% of fluorine mainly existed as HF/F− in leaching solution, which can provide theoretical guidance for further removal or recovery of F.