Selective recovery of platinum by combining a novel reusable ionic liquid with electrodeposition

In this study, five new imidazolium ionic liquids (ILs) were synthesized, and their efficiencies toward the precipitation of PtCl62- in HC1 media were evaluated. The prepared compounds were identified as 1-alkyl-3-propylimidazolium bromide ([C(n)Plm]Br, n = 12, 14, and 16), 1-tetradecyl-2-aminoethylimidazolium bromide ([C(14)PlmNH(2)]Br), and 1-tetradecyl-3-butylimidazolium bromide ([C(14)Plm]Br). FT-IR, H-1 NMR, and continuous variation method analysis were used to establish the ion-exchange model of Pt(IV) precipitation. To extract Pt (IV) from mixed metal solutions, and a novel mixed-ILs system was obtained through the dissolution of 1-tetradecyl-3-propylimidazolium bromide ([C(14)Plm]Br) in hydrophobic ILs ([C(8)Mlml] [PF6]). The mixed-ILs ([C(14)Plm] Br/[C(8)Mlm] [PF6]) exhibited excellent extraction efficiency compared to single [C(8)Mlm] [PF6]. Also, Pt(IV) ions were selectively separated from mixed metal solutions containing Rh(III), Fe3+, Ni2+, Cu2+, and Zn2+ metal ions. The separation factor beta(pt/m )(M: Fe, Ni, Cu, Zn, or Rh) was above 10(5) for all systems. The optimal potentiostatic deposition voltage of Pt was estimated to -1.75 V. Direct electrodeposition from ILs containing [C(14)Plm]Br/[C(8)Mlm] [PF6] with Pt(IV), more than 97% of Pt(IV) was reduced to Pt(0) on the copper cathode, while the system could also be regenerated for PtCl62- extraction. Surface characterization techniques like SEM, TEM, and XPS identified the deposited silver-grey films on cathode surfaces as Pt metal with metallic luster.

Automated summary

Five new imidazolium ionic liquids were synthesized and evaluated for their efficiency in precipitating PtCl62- in HCl media. A novel mixed-ILs system showed excellent extraction efficiency for Pt(IV) from mixed metal solutions, selectively separating Pt(IV) ions from metal ions of Rh(III), Fe3+, Ni2+, Cu2+, and Zn2+. Surface characterization techniques confirmed the successful electrodeposition of metallic Pt on the cathode surfaces.