Simultaneous extraction of Ti(IV) and Fe(III) in HCl solution containing multiple metals and the mechanism research

•Ti(IV) and Fe(III) were selectively recovered with only one extraction process.•The recovery rate of Ti(IV) and Fe(III) was close to 100%.•The extraction mechanism of Ti(IV) and Fe(III) was revealed in detail. A new process for simultaneous extraction of Ti(IV) and Fe(III) in HCl solution containing multiple metals was proposed, and the extraction mechanism was studied. The screened synergistic extractant had higher selectivity for Ti(IV) and Fe(III) than that of other metal ions. With four-stage countercurrent extraction in 1.5:1 phase ratio, the extraction efficiencies of Ti(IV) and Fe(III) were 99.76% and 99.99%, respectively. The extraction rates of co-extracted Ca, Al, V, Mg, Mn and Cr were 0, 0, 0, 0.32%, 1.44% and 31.49%, respectively. According to FT-IR spectra, speciation analysis and slope method, the mechanism of Ti(IV) extraction could be ionic association, the form extracted could be TiOCl32[ROHH2]¯. The mechanism of Fe(III) extraction was not only ion association, but also solvation, the forms extracted could be FeCl43C18H37NO3H3¯, FeCl4ROH3.33H¯ and FeCl3ROH3.33¯. Thermodynamic studies had also been conducted. The dilute HCl and deionized water were used as stripping agents, respectively. The Ti(IV) and Fe(III) stripping efficiencies were 99.88% and 99.90%, respectively. The purities of Ti(IV) solution and Fe(III) solution were 98.75 wt% and 99.18 wt%, respectively. The regenerated extractant would not lose activity. The proposed method may promote the industrialization of TiO2 produced by the HCl process.