This study introduces a new approach to extracting rare earth elements (REEs) from a Canadian ore concentrate, employing supercritical fluid extraction (SCFE) with supercritical carbon dioxide (sc-CO₂) as the solvent and a tributyl phosphate-nitric acid (TBP-HNO₃) adduct as the chelating agent. Addressing the environmental and safety concerns of traditional extraction methods, this research explores an eco-friendly and efficient SCFE technique, enhanced by a preliminary NaOH cracking step, to achieve nearly complete extraction efficiency of REEs. Characterization of the ore pre- and postextraction was thoroughly carried out using X-ray diffraction (XRD), scanning electron microscopy energy dispersion spectroscopy (SEM-EDX), and Raman Spectroscopy, revealing significant alterations in the mineralogical structure that facilitate the SCFE process. Focusing on the distribution and accessibility of REEs in feed concentrate, NaOH cracked samples, and SCFE residue, this investigation reveals the predominant presence of REE-bearing minerals in the initial and cracked samples, particularly within zircon structures. A notable transformation of iron from hematite to magnetite, absent in the feed but present in postprocessing samples, suggests a reduction process facilitated by high-temperature NaOH cracking. The findings emphasize the complexity of REE extraction from mineral matrices and the potential of integrating SCFE with NaOH cracking for improved results. The study optimized the operational parameters for NaOH cracking and SCFE, demonstrating their crucial role in maximizing REE efficiencies. An empirical model was used to quantify how these parameters influence extraction efficiency, providing insights into the SCFE process mechanisms and identifying optimal conditions. Our findings highlight the potential of SCFE as a sustainable alternative for REE extraction from primary resources with complex matrices. By significantly reducing hazardous waste and potentially utilizing atmospheric CO₂, this method aligns with global sustainability goals. This research not only contributes to advancing REE extraction technologies but also highlights the importance of exploring green chemistry solutions in critical material recovery for future technologies.

中文翻译：

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使用磷酸三丁酯-硝酸加合物从复杂矿石中优化稀土元素的超临界流体萃取


本研究介绍了一种从加拿大精矿中提取稀土元素 （REE） 的新方法，采用超临界流体萃取 （SCFE），以超临界二氧化碳 （sc-CO₂） 为溶剂，磷酸三丁基-硝酸 （TBP-HNO₃） 加合物作为螯合剂。为了解决传统提取方法的环境和安全问题，本研究探索了一种环保且高效的 SCFE 技术，并通过初步的 NaOH 裂解步骤得到增强，以实现 REE 的几乎完全提取效率。使用 X 射线衍射 （XRD）、扫描电子显微镜能量色散光谱 （SEM-EDX） 和拉曼光谱对矿石提取前后进行了彻底的表征，揭示了矿物结构的重大变化，从而促进了 SCFE 工艺。这项调查侧重于饲料精矿、NaOH 裂解样品和 SCFE 残留物中 REE 的分布和可及性，揭示了初始和裂解样品中含 REE 的矿物的主要存在，尤其是在锆石结构中。铁从赤铁矿到磁铁矿的显着转变，在原料中不存在，但存在于后处理样品中，表明高温 NaOH 开裂促进了还原过程。研究结果强调了从矿物基质中提取 REE 的复杂性以及将 SCFE 与 NaOH 裂解相结合以改善结果的潜力。该研究优化了 NaOH 裂解和 SCFE 的操作参数，证明了它们在最大限度地提高 REE 效率方面的关键作用。 使用实证模型量化这些参数如何影响提取效率，提供对 SCFE 工艺机制的见解并确定最佳条件。我们的研究结果强调了 SCFE 作为从具有复杂基质的原生资源中提取 REE 的可持续替代方案的潜力。通过显著减少危险废物并可能利用大气中的 CO₂，这种方法符合全球可持续发展目标。这项研究不仅有助于推进 REE 提取技术，还强调了探索绿色化学解决方案在关键材料回收中对未来技术的重要性。