Separation and recovery of scandium from high pressure sulfuric acid leach liquor of limonitic laterite

Abstract

Extraction of Sc from Sc-rich limonitic laterite without interfering with the main nickel-cobalt production circuit will significantly enhance the economic value of laterite. A process for separation and recovery of Sc from high pressure acid leach (HPAL) liquor of limonitic laterite was proposed in this paper. Based on the chemical composition of the leach liquor, precipitation thermodynamic analysis and experiments were conducted. The results indicated that after a first step to precipitate Fe3+ at pH = 2.5 and 90 °C, Sc could be enriched through a second step precipitate at pH = 4.8 and 60 °C to 267 g/t in Sc-containing precipitate. Then, Sc was re-leached from the Sc-containing precipitate via 1 mol/L sulfuric acid at L:S ratio of 5 mL/g, 80 °C, and 40 min. Meanwhile, gypsum in the Sc-containing precipitate transformed into calcium sulfate hemihydrate during leaching. After that, Sc was synergistically extracted from the leach solution via 5% P204 and 2.5% TBP. Moreover, impurities extracted into the organic phase during the extraction of Sc were scrubbed by HCl. Finally, Sc was stripped by NaOH. By using this process, Sc could be efficiently recovered from limonitic laterite in a facile way.