@article{oai:ynu.repo.nii.ac.jp:00009417,
 author = {Song, Yueqi and Tsuchida, Yusuke and Matsumiya, Masahiko and Uchino, Yuuki and Yanagi, Itaru},
 journal = {Minerals Engineering},
 month = {Nov},
 note = {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 H2SO4–H3PO4 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 → WO42− + 2Li+ + H2O 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[R3N]org + [HxWyOzn−]aq + n[H+]aq ⇔ [(R3NH)nHxWyOz]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 [Co2+]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.},
 pages = {224--229},
 title = {Separation of tungsten and cobalt from WC-Co hard metal wastes using ion-exchange and solvent extraction with ionic liquid},
 volume = {128},
 year = {2018}
}