Bauxite, as a significant carrier of critical metals, plays a crucial role in the efficient extraction of its associated resources, which is essential for the advancement of strategic emerging industries. This study employs a combination of experimental and density functional theory (DFT) calculations to systematically investigate the behaviour characteristics of diaspore substituted with different critical metal ions (Sr2+, Y3+, Ga3+) during flotation and leaching processes. In the experiments, sodium oleate (NaOL) was used as an anionic collector for flotation, while a HCl-NH4HSO4 composite leaching agent was employed for high-pressure acid leaching. The results indicate that the enrichment sequence of critical metal elements during flotation is Y > Sr > Ga, whereas the dissolution order of these ions under the same leaching conditions is Sr2+ > Y3+ > Ga3+.DFT calculations further elucidate the lattice strain and electronic property changes induced by lattice substitution. The reduced band gap following substitution provides additional channels for electron transfer by NaOL, thereby enhancing the flotation enrichment efficiency of the critical metals. Notably, Y3+ substitution significantly lowers the band gap and causes a substantial downward shift in the lowest unoccupied molecular orbital (LUMO) energy level, thereby strengthening collector adsorption and resulting in the highest flotation enrichment factor (EF). Mulliken charge analysis reveals the charge order of the substituting ions as Al3+ (+1.68 e) > Ga3+ (+1.67 e) > Y3+ (+1.53 e) > Sr2+ (+1.25 e). The lower charge density and reduced bond population of the Sr-O bond in Sr2+ maximally weaken the bonding strength, facilitating the easier detachment of Sr2+ from the diaspore lattice in the composite leaching agent. These findings are highly consistent with the enrichment and dissolution patterns observed in the experiments. This study provides a solid theoretical foundation for the efficient utilization of critical metals associated with bauxite.

中文翻译：

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关键金属离子晶格取代机制对铝土矿浮选分离和浸出行为的协同调控：实验和 DFT 计算

铝土矿作为关键金属的重要载体，在其相关资源的高效开采中发挥着至关重要的作用，这对于推进战略性新兴产业至关重要。本研究采用实验和密度泛函理论 （DFT） 计算相结合的方式，系统地研究了不同临界金属离子（Sr2+、Y3+、Ga3+）取代的散孢子在浮选和浸出过程中的行为特征。在实验中，油酸钠 （NaOL） 用作浮选的阴离子捕收剂，而 HCl-NH4HSO4 复合浸出剂用于高压酸浸出。结果表明，浮选过程中关键金属元素的富集顺序为 Y > Sr > Ga，而在相同浸出条件下，这些离子的溶解顺序为 Sr2+ > Y3+ > Ga3+。DFT 计算进一步阐明了晶格取代引起的晶格应变和电子性质变化。取代后带隙减小为 NaOL 的电子转移提供了额外的通道，从而提高了关键金属的浮选富集效率。值得注意的是，Y3+ 取代显著降低了带隙，并导致最低未占据分子轨道 （LUMO） 能级大幅下降，从而加强了捕集剂吸附并导致最高的浮选富集因子 （EF）。Mulliken 电荷分析揭示了取代离子的电荷顺序为 Al3+ （+1.68 e） > Ga3+ （+1.67 e） > Y3+ （+1.53 e） > Sr2+ （+1.25 e）。 Sr2+ 中 Sr-O 键的较低电荷密度和减少的键群最大限度地削弱了键合强度，有利于 Sr2+ 更容易从复合浸出剂中的尘生孢子晶格上分离。这些发现与实验中观察到的富集和溶出模式高度一致。本研究为铝土矿伴生关键金属的高效利用提供了坚实的理论基础。