Department of Chemistry, LAQV-REQUIMTE - Associated Laboratory for Green Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal.
Department of Chemistry, LAQV-REQUIMTE - Associated Laboratory for Green Chemistry, University of Aveiro, 3810-193, Aveiro, Portugal; LCA - Central Laboratory of Analysis, University of Aveiro, 3810-193, Aveiro, Portugal.
J Environ Manage. 2024 Sep;368:122211. doi: 10.1016/j.jenvman.2024.122211. Epub 2024 Aug 25.
The crucial role of Rare Earth Elements (REEs) in the development of hi-tech in addition to their limited availability have urged countries to develop sustainable alternatives to their conventional primary sources (ore mining). Sorption technologies using magnetic materials such as spinel ferrite nanoparticles provide efficient removal of REEs from contaminated solutions and ease of separation through application of an external magnetic field. However, there is still limited knowledge available regarding the optimal operational conditions in which to use these materials, especially in complex aqueous mixtures with different REEs. In this study, we have used Surface Response Methodology (SRM) applied to MnFeO nanosorbents to identify their ideal sorption conditions of pH (4-8), REEs concentration (1-5 μM) and sorbent mass (20-180 mg L) in a mixture of nine REEs in water samples of distinct salinity (NaCl: 0-30 g L). Our results indicated that high pH favored REEs sorption because of the material's surface charge, which promoted interactions with REEs ions at pH 6-8. Yttrium was the least removed element, but total removal was achieved for lowest REEs concentration using 151 mg L of sorbent. High removals were also obtained for the concentration of 5 μM (100 % removal, except for Y and La). Salinity did not impair sorption significantly (<10 %), which was owed to the high sorbent mass used in those assays. An increase in sorbent mass and initial REEs concentration also promoted faster kinetics. The spinel type MnFeO nanoparticles showed great promise in a realistic application, which is the next proposed step in this line of research.
稀土元素（REEs）在高科技发展中的关键作用，以及其有限的可用性，促使各国开发传统主要来源（矿石开采）的可持续替代品。利用尖晶石型铁氧体纳米颗粒等磁性材料的吸附技术，可从受污染的溶液中高效去除 REEs，并通过施加外部磁场轻松实现分离。然而，对于这些材料的最佳操作条件，尤其是在不同 REEs 的复杂水混合物中，目前仍知之甚少。在本研究中，我们使用表面响应方法（SRM）对 MnFeO 纳米吸附剂进行了研究，以确定其在混合九种 REE 的水样中理想的吸附条件，包括 pH（4-8）、REEs 浓度（1-5μM）和吸附剂质量（20-180mg/L），水样的盐度（NaCl：0-30g/L）不同。结果表明，高 pH 值有利于 REEs 的吸附，因为材料的表面电荷促进了在 pH 6-8 时与 REEs 离子的相互作用。钇是去除率最低的元素，但使用 151mg/L 的吸附剂，可实现最低 REEs 浓度的完全去除。对于 5μM 的浓度，也获得了较高的去除率（除 Y 和 La 外，去除率为 100%）。盐度对吸附的影响不大（<10%），这归因于在这些实验中使用的高吸附剂质量。吸附剂质量和初始 REEs 浓度的增加也促进了更快的动力学过程。尖晶石型 MnFeO 纳米颗粒在实际应用中显示出巨大的潜力，这是下一步研究计划。
