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).

Graphical Abstract

中文翻译：

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硫酸化焙烧-水浸下褐铁红土矿钪的浸出行为

本研究探讨了硫酸化焙烧-水浸 (SAL) 条件下褐铁矿红土中钪的浸出行为。褐铁矿的矿物学分析表明，钪与铁相有关。焙烧温度对硫酸化焙烧过程中的铁相转化起着重要作用。随着焙烧温度从100℃升高到800℃，铁相（针铁矿、磁铁矿和赤铁矿）逐渐转变为单斜晶Fe ₂ (SO ₄ ) ₃ (400 ℃)，然后转变为菱面体Fe ₂ (SO ₄ ) ₃（600°C），最后变成赤铁矿（800°C）。由于铁相转化机理，钪的浸出效率随着焙烧温度从100～800℃的升高先升高后降低。当褐铁矿在 600 °C 温度下焙烧 2 h，硫酸/红土比为 1/4 (mL/g) 时，在 30 ° 浸出液中总共提取了 81.15% 的钪和仅 0.37% 的铁C 以 4:1 (mL/g) 的液固比搅拌 1 小时。与高压酸浸 (HPAL) 相比，SAL 工艺能够从低品位褐铁矿中选择性和高效地富集钪，与高压酸浸 (HPAL) 相比，设备和操作成本更低，与常压酸浸相比，酸消耗更低，铁溶解更少（铝）。

图形概要