Separation of tungsten and cobalt from WC-Co hard metal wastes using ion-exchange and solvent extraction with ionic liquid. (November 2018)

• Record Type: Journal Article
• Authors: Song, Yueqi; Tsuchida, Yusuke; Matsumiya, Masahiko; Uchino, Yuuki; Yanagi, Itaru
• Is Part Of: Minerals engineering. Volume 128(2018)
• Page Start: 224
• Page End: 229
• Publication Date: 2018-11
• Subjects: Ion exchange -- Ionic liquid -- Solvent extraction -- Tungsten -- WC-Co hard metal; Mines and mineral resources -- Periodicals; Ressources minérales -- Périodiques; Mines and mineral resources; Periodicals; Electronic journals; 622
• DOI: 10.1016/j.mineng.2018.08.047
• Languages: English
• ISSNs: 0892-6875

Abstract

Highlights: A novel hydrometallurgical process was consisted of two step solvent extraction using ionic liquid. W(VI) was selectively extracted from WC-Co hard metal by [R3 N]/[P2225 ][NTf2 ], R = (CH2 )7 CH3 . The extraction mechanism of W(VI) was based on the ion association reaction. Co(II) was effectively extracted by PC-88A/[P2225 ][NTf2 ] at pH > 4.3 after removal of W(VI). [R3 N]/[P2225 ][NTf2 ] solvent was repeatedly applied on extraction-stripping process at 5th cycles. Abstract: Recently, the development of a process to separate W and Co from tungsten carbide-cobalt (WC-Co) hard metal wastes has become important. In this study, we proposed a novel hydrometallurgical process involving the following steps: pretreatment, leaching, ion exchange, and two-step solvent extraction (I) and (II) using ionic liquids (ILs). First, an AlCrN film coating was completely removed from a WC-Co hard metal sample by leaching in a H2 SO4 –H3 PO4 mixed acid medium at 423 K for 120 h. Then, the sample was oxidized at 1173 K for 10 h and XRD analysis showed that WO3 and CoWO4 were generated during this oxidization. After the oxidization, the leaching reaction WO3 + 2LiOH → WO4 2− + 2Li + + H2 O smoothly proceeded in leaching solution of 0.1 mol/L LiOH at 343 K for 19 h and the stoichiometry of WO3 :LiOH was 1:2, which was consistent with that of the leaching reaction. Further, after the leaching step was completed, it was beneficial to exchange H + and Li + in the leaching solution using a cation exchange resin. Solvent extraction was performed using triethyl- n -pentyl phosphonium bis(trifluoromethylsulfonyl)amide as the IL, and tri- n -octylamine was employed as the extractant for the selective separation of W(VI) for solvent extraction (I). The extraction percentages ( E ) of W(VI) and Co(II) were >95% and <2.5% at pH = 1.0, respectively, and the selective extraction of W(VI) was confirmed in this study. The extraction mechanism of W(VI) was based on the ion association reaction n [R3 N]org + [H x W y O z n − ]aq + n [H + ]aq ⇔ [(R3 NH) n H x W y O z ]org . In solvent extraction (II), a PC-88A/[P2225 ][NTf2 ] system was used for the effective extraction of Co(II) at pH > 4.3. The slope analysis results showed that the extraction mechanism was governed by the cation exchange reaction [Co 2+ ]aq + 2[(HL)2 ]org ⇔ [CoL2 ·2HL]org + 2[H + ]aq . A series of novel hydrometallurgical process using IL enabled us to demonstrate that W(VI) and Co(II) were efficiently recovered from WC-Co hard metal wastes.