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

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.