Supercritical fluid extraction is receiving growing attention for the enhanced extraction and separation of metals. A metal must be charge neutral and coordinatively ready to dissolve in non-polar supercritical carbon dioxide (sc-CO₂). This can be accomplished by bonding the metal with a combination of negative and neutral ligands. Here, we investigate the effect of four organophosphorus reagents including triethyl phosphate (TEP), tri-n-butyl phosphate (TBP), tributyl phosphine oxide (TBPO), and trioctyl phosphine oxide (TOPO), on the extraction of neodymium from a neodymium-iron-boron magnet in sc-CO₂. The COSMO-vac model is used to predict the solubility of these reagents in sc-CO₂ showing the order of TEP > TBPO ~ TBP > TOPO. The stoichiometry of Nd-ligand complexes is determined via UV-Vis spectroscopy, showing a 1:1 Nd–TEP, 1:3 Nd–TBP, 1:3 Nd-TBPO, and 1:4 Nd–TOPO complex chemistry. Highest neodymium extractions are achieved with TEP followed by TBP, TBPO, and TOPO, respectively. This is due to the increase in coordination number which results in more hydrophobic interactions between aliphatic functionalities, leading to larger micellar assemblies with lower solubility in sc-CO₂, which result in lower extraction efficiency.

超临界流体萃取对于增强金属的萃取和分离越来越受到关注。金属必须是电荷中性的，并且必须能协调地溶解在非极性超临界二氧化碳（sc-CO ₂）中。这可以通过将金属与负和中性配体结合而实现。在这里，我们研究了四种有机磷试剂，包括磷酸三乙酯（TEP），磷酸三正丁酯（TBP），三丁基氧化膦（TBPO）和三辛基氧化膦（TOPO），对从钕中提取钕的影响-CO- _2中的铁硼磁铁。COSMO-vac模型用于预测这些试剂在sc-CO _2中的溶解度显示TEP> TBPO〜TBP> TOPO的顺序。Nd-配体配合物的化学计量是通过紫外-可见光谱确定的，显示出1：1 Nd–TEP，1：3 Nd–TBP，1：3 Nd-TBPO和1：4 Nd–TOPO配合物化学。使用TEP最高的钕提取率分别是TBP，TBPO和TOPO。这是由于配位数的增加，这导致脂族官能团之间发生更多的疏水相互作用，从而导致较大的胶束组装体在sc-CO _2中的溶解度降低，从而导致提取效率降低。