Method for preparing vanadium oxide

The invention provides a method for preparing vanadium oxide, which comprises the following steps of: mixing vanadium slag with calcium oxide or limestone to form a mixed material; roasting the mixed material to obtain calcified clinker; leaching the calcified clinker by using C2O4 and 35-70 g/L of oxalate solution at 80-95 DEG C; after leaching, carrying out solid-liquid separation to obtain vanadium-containing leachate and residues; removing silicon from the vanadium-containing leachate, so that the silicon concentration in the vanadium-containing leachate is less than 0.1 g/L, then adding ammonium oxalate into the vanadium-containing leachate, adjusting the mol ratio of NH4 to TV to 2-3.5, precipitating ammonium metavanadate, and filtering to obtain ammonium metavanadate and vanadium precipitation wastewater; and oxidizing, roasting and deaminizing ammonium metavanadate to prepare vanadium pentoxide or reducing to prepare vanadium trioxide. According to the invention, on the premise of satisfying environment-friendly requirements, preparation of vanadium oxide from ordinary vanadium slag and high-calcium and high-phosphate vanadium slag is realized; furthermore, consumption of reagents can also be reduced; and the production cost is reduced.