Separation of vanadium and iron from the steelmaking slag convertor using Aliquat 336 and D2EHPA: Effect of the aqueous species and the extractant type

•For efficient separation of V and Fe, transformation of ferric to ferrous was found essential.•V+4 and V+5 species were both extracted through cation exchange reactions.•Through anion exchange reactions, only V+5 species were extracted.•Proper aqueous species of V/Fe were prepared prior to SX, through leaching and cementation operations.•Flow diagram of vanadium recovery from convertor slag was proposed. In this study, a selective process for separation of vanadium and iron from the steelmaking slag was proposed. The proposed process has a potential to be considered industrially due to its relative simplicity. The process for the separation of vanadium and iron is consisted of three main stages: leaching, cementation, and solvent extraction. The leaching and cementation stage, were designed such that the proper aqueous species of vanadium and iron for the solvent extraction stage got generated. In the solvent extraction experiments, the effect of vanadium and iron aqueous species and the extractant type (extraction through anion and cation exchange reactions) on the separation of these elements were studied. In the solvent extraction stage, D2EHPA (cationic exchange) and Aliquat 336 (anionic exchange) were used. The results, for both extractants, showed that for selective separation of vanadium and iron, conversion of ferric to ferrous is essential. By converting ferrous to ferric ion, almost no iron was extracted through the anion exchange. Through cation exchange, however, ferrous extraction was started at significantly higher pH values comparing to ferric ion. D2EHPA was shown to have the ability to extract vanadium with both oxidation states of +4 and +5. Aliquat 336, however, showed no extraction toward V+4, and only extracted V+5 species. This was found due to the absence of anionic complexes of V+4 in a sulfuric acid solution. The extraction mechanism of vanadium through both anion and cation exchange reactions were studied. The results showed the formation of VO2R(RH) through cationic extraction and VO2SO4R4N for the anionic extraction. Finally, 90% vanadium stripping efficiency from D2EHPA and Aliquat 336 loaded organics were obtained using 2 M H2SO4 and 3 M HCl solutions, respectively.