Recovery of vanadium from acid leaching solutions of spent oil hydrotreating catalyst using solvent extraction with D2EHPA (P204)

In this paper, a process of selective extraction and separation of vanadium (IV) from acid leaching solution of spent oil hydrotreating catalyst by a solvent extraction method with P204 as an extractant was proposed. Because the leaching solution contained a large amount of elements such as nickel, aluminium and iron, the effects of various conditions on the separation of vanadium from nickel, aluminium and iron were investigated and the optimum conditions were determined. At the same time, the thermodynamic discussion on the extraction process of vanadium in the system was carried out. Using kerosene as a diluent and 20% (v/v) P204 as an extractant, the single-stage maximum extraction ratio of 93.47% for vanadium was obtained under the optimum extraction conditions of O/A ratio of 2, oscillation time of 8 min, extraction temperature of 298 k(25 degrees C) and pH value of initial aqueous phase of 2. After three stages of countercurrent extraction experiments, the concentration of vanadium, iron, nickel and aluminium in the loaded organic phase were 0.377, 0.001, 0.005 and 0.02 g/L, respectively, and their extraction ratios were determined to be 99.21%, 1.02%, 2.857% and 1.942%, respectively, realizing the selective extraction and separation of vanadium. With 2 mol/L of sulfuric acid as a stripping reagent, the complete removal of vanadium from the loaded organic phase could be achieved at O/A ratio of 2 by three stages of countercurrent experiments of vanadium removal. The thermodynamic calculation showed that the enthalpy change of the vanadium extraction in the system was -20.37 kJ.mol(-1). This demonstrated that the extraction of vanadium from acid leaching solution of spent oil hydrotreating catalyst with P204 as the extractant was an exothermic reaction.