Abstract
SCS pincer ligands 1–4 were synthesised, and their ability to extract Pd(II) from HCl and HNO3 media was studied. The Pd(II) extraction properties of 1–4 were compared with those of commercial extractants (DOS and LIX®84-I) in kerosene. 1 and 2 showed superior Pd(II) extractability (E% = 99.9) relative to DOS and LIX®84-I from 0.1–8.0 M HCl and to DOS from 0.1–8.0 M HNO3 and mixed HCl + HNO3 media. The Pd(II) extraction rate, acid durability, the most suitable organic/aqueous (O/A) phase ratio, and Pd(II) loading capacity of extractants 1, 2, and DOS were evaluated. 1 and 2 exhibited a greater Pd(II) extraction rate and Pd(II) loading capacity than DOS. 1 was very stable in acid media (HCl and HCl + HNO3), whereas 2 and DOS deteriorated in HCl + HNO3. Selective extraction of Pd(II) by 1 and 2 was achieved from a mixed solution containing Pd, Pt, Rh, rare metals, and base metal ions that simulated the leach liquors of automotive catalysts. The back extraction of Pd(II) and reusability of extractants 1 and 2 were studied. The Pd(II) extraction mechanism of 1–4 was investigated using FT-IR, UV-visible, and NMR spectroscopy.
Highlights
The Pd(II) extraction rate, acid durability, the most suitable organic/aqueous (O/A) phase ratio, and Pd(II) loading capacity of extractants [1, 2], and di-n-octyl sulphide (DOS) were evaluated. 1 and 2 exhibited a greater Pd(II) extraction rate and Pd(II) loading capacity than DOS. 1 was very stable in acid media (HCl and HCl + HNO3), whereas 2 and DOS deteriorated in HCl + HNO3
The E% of all extractants decreased with increasing HCl concentration
The experimental results show a distinct dependence of E% on HCl concentration and extractant structure
Summary
Selective extraction of Pd(II) by 1 and 2 was achieved from a mixed solution containing Pd, Pt, Rh, rare metals, and base metal ions that simulated the leach liquors of automotive catalysts. Germany) carry out hydrometallurgical refining by leaching precious metals from concentrated primary and secondary sources using HCl + Cl21, 11. ® (DHS), di-n-octyl sulphide (DOS), and 2-hydroxy-5-nonylacetophenone oxime (LIX 84-I)[1, 11] are used in the solvent extraction process These reagents are useful in separating Pd(II) and Pt(IV), they are not without issues regarding extraction rate, selectivity, and durability. The kinetics of Pd(II) extraction using LIX 84-I are extremely slow, and it is necessary to use an organic amine as an accelerator to increase the extraction rate[1]
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