Extraction of Vanadium in the Comprehensive Recycling of Spent Al₂O₃-Based Catalyst

Abstract

Under the premise of comprehensive recycling valuable metals, a novel technology was developed to extract vanadium from spent Al2O3-based catalyst. Mixture of spent catalyst and sodium carbonate was roasted at 1000°C for 30 min with the mol ratio of Na2O to (Al2O3 + V2O5 + MoO3) as 1.15, after water leaching, 97.3% of vanadium could be extracted. With CaO addition of 25 g/L and reacting at 90°C for 4 h, 98.6% of vanadium in sodium aluminate solution was precipitated as desilication residue. The desilication residue was leached at 80°C for 45 min with sodium bicarbonate concentration of 100 g/L and L/S of 4 mL/g, over 96.4% of vanadium could be leached. By two purification steps with addition of 30 wt.% H2SO4 and Mg(NO3)2, respectively, over 99% of Al, 96% of Si, 93% of P and 95% of As were removed from leach liquor. Adding 50 g/L NH4NO3 to the purified leach liquor and adjusting pH to 8.2, 99.8% of vanadium could be precipitated as ammonium metavanadate. After calcination, the purity of V2O5 product was 98.25%. In the whole process, up to 88.7% of vanadium could be recovered from the spent catalyst.