Recovery of platinum by solvent extraction and direct electrodeposition using ionic liquid

The diluent characteristics and the wide electrochemical window of the ionic liquid (IL), triethyl-n-hexyl phosphonium bis(trifluoromethyl-sulfonypamide; [P-2225] [NTf2], has been exploited for the extraction of Pt(IV) using trl-n-octylamine (TOA, R3N, R = (CH2)(7)CH3) hydrochloride, followed by direct electrodeposition as Pt metal from organic phase. The extraction mechanism of Pt(IV) with [R3N center dot HCl]/[P-2225] [NTf2] has been investigated from the slope analysis. As a result, it was revealed that the extraction mechanism of Pt(IV) was based on the following anion exchange extraction; [PtCl62-](aq) + 2[R3N center dot HCI](org) double left right arrow[R3NH](2)[PtCl6](org) + 2[Cl-](aq) (R = (CH2)(7)CH3) The viscosity and the ionic conductivity for the [R3NH](2)[PtCl6] were satisfied by Vogel-Fulcher-Tamman (VFT) equation and each best -fit parameter can be estimated in this study. The electrochemical behavior for [R3NH](2)[PtCl6] in IL was investigated by Electrochemical Quartz Crystal Microbalance (EQCM) at 373 K. It was revealed that the cathodic reaction: Pt(IV) + 2e(-) -> Pt(II) was estimated from 0 V to -0.87 V and Pt (II) + 2e(-) -> Pt(0) was proceeded from - 0.87 V to -1.13 V considering from M-app = 178.5 evaluated by CV/EQCM. Moreover, the alternation of Delta eta rho (product of viscosity and density) was corresponded to the locally decrease of the viscosity of IL near the electrode. Finally, the potentiostatic electrodeposition of [R3NH](2)[PtCl6] allowed us to recover the blackish electrodeposits, which were identified as most of Pt metal by EDX and XRD analyses.