Selective solvent extraction of vanadium over iron from a stone coal/black shale acid leach solution by D2EHPA/TBP

A D2EHPA and TBP mixed solvent system diluted with kerosene were used for the selective extraction of vanadium(IV) from iron(II) from an acidic stone coal leach solution that was reduced using sodium sulfite. Extraction studies were carried out under different pH and solvent concentrations, and optimized conditions were determined. The loaded organic was stripped with sulfuric acid. The number of stages required for the extraction and stripping of vanadium were determined from a McCabe-Thiele plot and confirmed by counter-current simulation studies. Results demonstrate that the extraction of vanadium increases as the initial pH and the D2EHPA concentration increases in the organic phase. A six-stage counter-current extraction simulation test was conducted over a period of 40 h at a initial pH of 2.48 with 10% (v/v) D2EHPA and 5% (v/v) TBP mixed extractant and resulted in a vanadium extraction of 97% for the feed solution containing 5.78 g/L V2O5 and 10.86 g/L total Fe. The loaded organic phase that contained 5.34 g/L V2O5 and 1.0 g/L Fe can be completely stripped by three-stage counter-current stripping with 1.5 mol/L H2SO4 at a phase flow ratio of O/A = 5:1 to give a strip solution containing 26.3 g/L V2O5 and 0.72 g/L Fe.