Efficient recovery of some valuable elements from syenogranite, Ras Abda, North Eastern Desert, Egypt
摘要
This study investigates the sulfation roasting–water leaching behavior and recovery of valuable elements from Syenogranite sourced from Ras Abda, in Egypt's North Eastern Desert. The ore contains 375 mg/kg of U, 7.9 g/kg of Th, 7 g/kg of total rare earth elements (TREEs), and 4.1 g/kg Zr. Sulfation roasting with H2SO4 was carried out at an acid-to-ore ratio of 500 kg/t, a roasting temperature of 443 K and a roasting time of 120 min, followed by water leaching for 90 min at room temperature using a solid-to-liquid ratio of 1/5. Under these optimum conditions, the leaching efficiencies reached 84% for U, 93.5% for Th, 99% for LREES, 95% for HREES, and 93% for Zr. The leaching kinetics followed the shrinking core model, with diffusion through the product layer governing the leaching processes. The calculated activation energies were 9.5, 8.2, 2.66, 5.44, and 9.991 kJ mol−1 for U, Th, LREES, HREES and Zr, respectively, confirming the effectiveness of sulfation roasting in enhancing the leachability of the investigated elements. Thorium and REEs were recovered through oxalic acid precipitation, after which thorium was selectively separated from the oxalate cake via alkaline leaching. The sulfate leach liquor, free from Th4+ and REE3+ ions, was pH adjusted to 1.8 and subjected to solvent extraction with 20% TBP to remove interfering ions such as U4+ and Fe2+ prior to zirconium recovery. Zirconium was finally precipitated directly from the raffinate at pH 3.5 using NaOH.