Extraction of lithium from lepidolite via iron sulphide roasting and water leaching

• Lithium was recovered from lepidolite via FeS–CaO roasting and water leaching.
• HSC was used to simulate the thermodynamics taking place during roasting.
• Lithium was extracted from lepidolite via interaction with SO2/SO3.
• Approximately 81% lithium was extracted from lepidolite into a sulphate solution.
• High loss of S caused low Li extraction and diluted liquors.

In this study, lithium was recovered from lepidolite via iron sulphide (FeS)–CaO roasting and water leaching. The thermodynamics taking place during the roasting of lepidolite and the additives was simulated by using the HSC programme. The simulation indicates that SO2/SO3 formed from the oxidation of FeS plays an important role in extracting lithium from lepidolite. Roasting at 750 °C using FeS/Li and Ca/F molar ratios of 5:1 and 1:1, respectively, followed by leaching at 50 °C using water/calcine mass ratios of > 5:1 could yield a maximum of 81% Li recovery (at < 1 g/L Li concentration). It was found that 71.5% of S was liberated into the atmosphere, resulting in lower extraction of Li and more diluted leach liquors compared to those obtained during closed-system roasting of lepidolite and Fe sulphate mixes.