Hydrophobic deep eutectic solvents (DESs) are considered to be clean and green alternatives to traditional organic solvents for metal ion extraction. Herein, a series of novel hydrophobic DESs were synthesized via the combination of methyltrioctylammonium chloride ([N₈₈₈₁]Cl) as hydrogen bond acceptors (HBAs) and saturated fatty acids or saturated fatty alcohols as hydrogen bond donors (HBDs). Then, the DESs were used for palladium(II) recovery from acid solution. The factors that affect palladium(II) extraction (including the DES species, contact time, DES dose, solution pH, and temperature) were extensively investigated. The DESs exhibit excellent performance for extracting palladium(II) from hydrochloric acid media, and more than 99% of palladium(II) was extracted under optimal conditions. UV–vis, ¹H NMR, and FTIR spectral characterizations confirm that the extraction mechanism of palladium(II) involves an anion exchange reaction whereby PdCl₄²⁻ anions in the aqueous phase replace Cl⁻ anions in DES to form ion-pairs with $\left[N_{8881}^{+}\right]$ via electrostatic interactions. Meanwhile, N₈₈₈₁Cl:1-hexanol (1:1) and N₈₈₈₁Cl:hexanoic acid (1:2) exhibit excellent selectivity for palladium(II) over other impurity metal ions. Also, palladium(II) in the loaded DES phase was efficiently recovered as elemental palladium via the hydrazine hydrate reduction method; thus, the DES could be reused for at least 5 cycles.

疏水性深共晶溶剂（DES）被认为是用于金属离子萃取的传统有机溶剂的绿色清洁替代品。在此，通过结合作为氢键受体（HBA）的甲基三辛基氯化铵（[N ₈₈₈₁ ] Cl）和作为氢键供体（HBD）的饱和脂肪酸或饱和脂肪醇，合成了一系列新型疏水性DES 。然后，将DES用于从酸性溶液中回收钯（II）。广泛研究了影响钯（II）提取的因素（包括DES种类，接触时间，DES剂量，溶液pH值和温度）。DES具有优异的从盐酸介质中萃取钯（II）的性能，并且在最佳条件下萃取出99％以上的钯（II）。紫外线可见¹ H NMR，FTIR和光谱表征确认钯（II）的提取机制涉及阴离子交换反应，由此的PdCl ₄ ^2-阴离子在水相中取代氯^-与阴离子在DES到形式离子对$\left[{ñ}_{8881}^{+}\right]$通过静电相互作用。同时，N ₈₈₈₁ Cl：1-己醇（1：1）和N ₈₈₈₁ Cl：己酸（1：2）对钯（II）的选择性优于其他杂质金属离子。另外，通过水合肼还原法有效地回收了负载的DES相中的钯（II）作为元素钯。因此，DES可以重复使用至少5个周期。