Recovery of ruthenium by solvent extraction and direct electrodeposition using ionic liquid solution

Abstract

It is important to recover Ru metal from spent target materials including Pt, Co and Cr. The extraction behavior using Di-(2-ethylhexyl)phosphoric acid (HDEHP) and ionic liquid (IL), triethyl-n-pentyl phosphonium bis(trifluoromethylsulfonyl)amide ; [P2225][TFSA] diluent was investigated with pH dependence. Co(II) and Cr(II) were selectively extracted into the organic phase because the extraction of Co(II) and Cr(II) proceeded by cation exchange. As a result, Pt(IV) and Ru(III) can be separated from Co(II) and Cr(II) by controlling the pH. Moreover, the extraction mechanism of Ru(III) with the Alamine336 (A336)/[P2225][TFSA] system was based on the following anion exchange reaction; [R3NH+Cl-]org + [RuCl4(H2O)2-]aq ⇔ [R3NH+RuCl4(H2O)2-]org + [Cl-]aq, (R = CH3(CH2)7-/CH3(CH2)9-). The electrochemical behavior for Ru(III) in the [P2225][TFSA] was investigated by cyclic voltammetry at 373 K. It was revealed that two step cathodic reactions: Ru(III) + e-→ Ru(II) and Ru(II) + 2e-→ Ru(0) were proceeded in the [P2225][TFSA] system. Moreover, the potentiostatic electrodeposition allowed us to recover the blackish electrodeposits, which were identified as most of Ru metal by EDX analysis. Finally, we investigated the reuse of the Ru(III) in A336/IL solvent for continuous extraction and electrodeposition. The extraction percentage of Ru(III) using A336/IL remained relatively high (81.5−96.1%) for the 1st−5th cycles. This series of experimental results enabled us to demonstrate that Ru metal can be obtained from direct electrodeposition of the extracted [R3NH+RuCl4(H2O)2-] in the A336/[P2225][TFSA] system.

Recovery of Pd(II) from Hydrochloric Acid Medium by Solvent Extraction–Direct Electrodeposition Using Hydrophilic/Hydrophobic ILs

“…In the last decade, electrodeposition has been widely used for the purification and separation of metal ions. Many studies have reported the recovery of metals such as Cu, 22 Sr, 23 U, 24 Pt, 25 and Ru 26 through solvent extraction–direct electrodeposition. Compared with the conventional organic phase back-extraction method, direct electrodeposition can reduce the use of volatile organic solvents.…”

“…In the last decade, electrodeposition has been widely used for the purification and separation of metal ions. Many studies have reported the recovery of metals such as Cu, 22 Sr, 23 U, 24 Pt, 25 and Ru 26 1a). The characteristic UV−Vis absorption peaks of Pd(II) aqueous solution appeared at 222 and 280 nm (Figure 1b).…”

Electroanalytical Chemistry of Lanthanides/Actinides and the Feasibility of Direct Electrodeposition in Ligand Containing Ionic Liquids: A Comprehensive Review

“…As compared to the electrodeposition study in only ionic liquid medium, there are few reports dealing with the feasibility of direct electrodeposition from the ligand/IL mixture. 61,62,65,66 The authors have claimed different deposition potentials depending on the nature of ionic liquid and the feed acidity used. A schematic of the direct electrodeposition of the metal ion from the ligand containing IL phase is shown in Fig.…”

Electrodeposition Behavior of Extracted Platinum Complex in Phosphonium-Based Ionic Liquids Evaluated by Electrochemical Quartz Crystal Microbalance

“…From the standpoint of recovery, this combination method has several advantages such as simple construction, less secondary waste, and easy handling. We demonstrated the recovery of In [14], Fe [15], and Ru [16] by the combination of solvent extraction and direct electrodeposition using phosphonium-based ILs. However, the recovery of Pt metal by the extractionelectrodeposition method has not been reported so far.…”