Selective separation of vanadium from the high-acidity leaching liquor through chelating extraction by the ketoxime extractant

The high-acidity vanadium-containing solution contains high concentrations of iron and aluminum with pH around 0.5, the ketoxime extractant with the active ingredient of 2-hydroxy-5-nonylacetophenone oxime (HNAO, HL) was proposed to extract vanadium from the solution. Under the phase ratio (O/A) of 1:2, HNAO concentration of 0.542 mol·L −1 at 25 °C for 10 min, 99.06% of vanadium was extracted after a three-stage countercurrent extraction, while the extraction of impurities was less than 1%, with the separation coefficients of vanadium from iron and aluminum were 137050 and 43197, respectively. The antioxidant properties of the extractant were studied. At 25 °C, the extractant basically did not undergo oxidative degradation. Besides, about 91.2% of the loaded vanadium was effectively stripped using 2.5 mol·L −1 Na 2 CO 3 solution. The extraction mechanism of vanadium was investigated through the slope analysis method, the spectral characterizations and density functional theory calculations. It has been observed that VO 2 + substitutes the H atom on the phenolic hydroxyl and coordinates with the N atom on the oxime and the O atom on the phenolic hydroxyl to form of a six-membered ring, and the extraction complexes were determined to be VO 2 (H 2 O)L and VO 2 L.