Vanadium (V) extraction in systems with quaternary ammonium salts

Abstract

Vanadium (V) extraction with quaternary ammonium salts from neutral and slightly alkaline solutions was studied. It was shown that in all systems at pH = 5.0...9.0, i.e. in the region of the existence of metavanadate ions, the degree of vanadium extraction is close to 100 %. The cationic part of the extractants does not significantly affect the recovery of V, the type of anion in the extractant is determining. Stripping of vanadium with PAO salts is difficult and takes place in a solid-phase version regardless of the type of stripping agent (NH4Cl, NaOH or NH4HCO3), which is a significant drawback. New extraction systems based on trialkylmethylammonium chloride or trialkylmethylammonium sulfate (TAMAS) with paraalkylphenol have been studied. In these systems, along with highly efficient extraction, efficient stripping with NaOH solutions in a two-phase system is realized, which allows to obtain concentrated vanadium stripping without precipitation and ensures its high recovery from the organic phase. The ease of stripping is due to the formation in the organic phase of trialkylmethylammonium phenolate. The extractant is regenerated by treating the organic phase with solutions of acid solutions (H2SO4) or NH4HCO3. The results of pilot tests on the extraction of V from leaching solutions of spent vanadium sulfuric acid catalysts containing; g/dm3: 7.13 V; 0.012 P; 0.08 As and 0.35 SiO2 with a 0.2 M solution of TAMAS mixed with 0.4 M paraalkylphenol in kerosene + 15% 2-ethylhexanol, and stripping of V with 1.5 M NaOH solution showed high efficiency of this system. For the 4 stage of extraction and 2 stripping, the degree of vanadium extraction was 99.7%. Obtained from a re-extract vanadium pentoxide met the requirements of TU brand VNO-1.