Extraction of iron (III) from chloride leaching liquor with high acidity using tri-n-butyl phosphate and synergistic extraction combined with methyl isobutyl ketone

• Iron was effectively separated from high acidity chloride liquor with many ions.
• Synergistic coefficient of 2.23 was obtained by using TBP and MIBK extractant.
• Influence factors in extraction and stripping processes were investigated in detail.
• Iron extraction and stripping in one stage were above 91.0% and 89.0%, respectively.
• Mechanism on iron extraction by mixed extractant was studied based on FT-IR spectra.

Separation of iron (III) from simulated chloride leaching liquor with high acidity by tri-n-butyl phosphate (TBP) and methyl isobutyl ketone (MIBK) extraction was investigated. Synergistic effect in iron extraction was found using TBP and MIBK extractant and evaluated by synergistic enhancement coefficient. Based on the physical properties and extraction ability of organic phase, the suitable composition was 70 vol.% TBP and 30 vol.% MIBK. Iron extraction increased with an increase in HCl concentration from 4.22 mol/L to 7.74 mol/L. Under optimal extraction conditions, that is, TBP volume fraction 70%, contact time 2 min, temperature of 25 °C, and phase ratio (O/A) 1:1, the iron extraction in one stage was above 91.0% with initial HCl concentration 5.1–5.5 mol/L and iron concentration 36–39 g/L, consistent with the practical chloride leaching liquor. Results showed that negligible metal ions Cr, V, Ca, Mg, Al, Mn, Ti and Si were co-extracted. The loaded organic phase can be effectively stripped by 0.1 mol/L ammonia compared with other stripping reagents. Under the optimal stripping conditions: contact time 2 min, reaction temperature 25 °C, and phase ratio (A/O) 2:1, more than 89.0% of iron was stripped in one stage so the organic phase could be regenerated. The Fe2O3 product with high purity was prepared from the stripping solution by precipitation and calcination processes. The mechanism of iron (III) extraction using synergistic system was discussed according to FT-IR spectra results.