Selective sorption of palladium by thiocarbamoyl-substituted thiacalix[n]arene derivatives immobilized on amberlite resin: application to leach liquors of automotive catalysts

Abstract

p-tert-Butylthiacalix[4/6]arenes (1 and 2) and their thiocarbamoyl derivatives (3 and 4) were immobilized on Amberlite XAD-7 (XAD). Pd(II) adsorption from single-metal solution, simulated mixed-metal solution, and automotive catalyst leach liquor in HCl media was performed in the batch mode. The Pd(II) sorption capacity of 3 and/or 4 immobilized on XAD (7 and 8) was 40.2 mg g⁻¹ and 60.0 mg g⁻¹, respectively. In contrast, 1 and/or 2 immobilized on XAD (5 and 4) had lower sorption capacities than 7 and 8, 10.1 mg g⁻¹ and 13.4 mg g⁻¹, respectively. Resins 7 and 8 selectively sorbed 99% of Pd(II) ions from automotive catalyst liquor comprising Rh, Pd, Pt, Zr, Ce, Ba, Al, La, and Y in 0.1 M HCl media. XAD and the extractant-impregnated XAD resins were characterized by FT-IR, XRD, SEM-EDAX, and WDXRF before and after Pd(II) sorption. The sorption data were fitted to Freundlich and Langmuir isotherms. Thermodynamic parameters such as ΔG^o, ΔH^o, and ΔS^o were calculated to evaluate the nature of the sorption process. The Pd(II) sorption efficiency of 7 and 8 was also tested by column method. Desorption of Pd(II) ions from the loaded resins was performed using acidic thiourea, thereby enabling recycling of the resins. Thus, both resins 7 and 8 can be used for the effective separation of Pd(II) from secondary resources.