Studies on recovery of vanadium from desilication residue obtained from processing of a spent catalyst

Recovery of vanadium from desilication residue obtained from the processing of a spent catalyst was investigated by leaching, purification and precipitation. In the leaching process, 96.4% vanadium can be extracted when the desilication residue (1:4 g/mL) was stirred at 800 rpm for 45 min at 80 °C with 100 g/L sodium bicarbonate. After purifying leach liquor in a two stage precipitation process, over 99% Al, 95% Si, 93% P and 95% As were removed under optimum conditions with less than 4% loss of vanadium. Adding 50 g/L NH4NO3 to the purified leach liquor and adjusting the pH to 8.2, promoted the crystallization and precipitation of 99.7% vanadium as ammonium metavanadate. After roasting ammonium metavanadate at 500 °C for 2 h, the purity of the V2O5 product was up to 98.3%. In terms of desilication residue and spent catalyst, the recovery of vanadium in the process reached 92.5% and 88.7%, respectively. The proposed leaching, purification and precipitation steps provide a feasible recovery of vanadium from desilication residue and a new approach for the comprehensive utilization of spent catalyst.