<p>New understanding of extraction and separation of vanadium(IV), iron and titanium using iron powder induction-leaching and P204-P507 synergistic extraction</p>

Herein, we investigated the induced-leaching behavior of hematite by iron powder after ammonium sulfate roasting vanadium titanomagnetite concentrate and develop a P204-P507 synergistic extraction method for separation of vanadium(IV), iron and titanium. The results showed that the effective selective separation of vanadium, iron and titanium could be obtained in which 97.39 % V and 88.62% Fe were dissolved into the solution and over 91.76% Ti was remained in leaching residue after leaching at 0.5 M H2SO4, 110 ?& nbsp;for 1 h, then added 10% iron powder and continue to leaching for 2 h. Tafel polarization curve and impedance spectroscopy both proved that iron powder could reduce the chemical reaction resistance and accelerate the ion transfer rate in the leachate. Based on the speciation analysis by Medusa software, the speciation distribution of vanadium, iron and titanium in the sulfuric acid system eventually exists in the form of VO(2+ )and Fe(II) ions, while most of titanium precipitates to the leaching residue in the form of TiO2. The five stages countercurrent extraction test was carried out to confirm the prediction of McCabe-Thiele diagram, and the extraction efficiency of vanadium reached 98.13% under the condition of mixed extractant concentration of 15%, v(P204):v(P507) of 3, pH of 1.8 and phase ratio (O/A) of 2.0. The slope method proved that P204-P507 molecule could release two H+ ions for every vanadium ion extracted, which could be attributed to the cation exchange reaction. Finally, a high-titanium slag with a TiO2 content of 85.32% was obtained by alkaline leaching method