Leaching Behavior of Scandium from Limonitic Laterite Ores Under Sulfation Roasting–Water Leaching

Abstract

In the present study, the leaching behavior of scandium from limonitic laterites under sulfation roasting–water leaching (SAL) was explored. The mineralogical analysis of limonitic laterites showed that scandium was associated with the iron phase. The roasting temperature played an important role in the iron phase conversion during the sulfation roasting process. With an increase in the roasting temperature from 100 to 800 °C, the iron phase (goethite, magnetite, and hematite) gradually converted to monoclinic Fe2(SO4)3 (400 °C), then to rhombohedral Fe2(SO4)3 (600 °C), and finally to hematite (800 °C). Due to the iron phase conversion mechanism, the leaching efficiency of scandium gradually increased first and then decreased with the increase of roasting temperature from 100 to 800 °C. When limonitic laterites roasted at temperature of 600 °C for 2 h with sulfuric acid/laterite ratio of 1/4 (mL/g), a total of 81.15% of scandium and only 0.37% of iron were extracted into leaching solution at 30 °C with the liquid-to-solid ratio of 4:1 (mL/g) for 1 h with agitation. The SAL process enables the selective and efficient enrichment of scandium from low-grade limonitic laterites with lower costs for equipment and operation compared to high-pressure acid leaching (HPAL), lower acid consumption, and lower dissolution of iron compared to atmospheric pressure acid leaching (AL).