Synthesis of vanadium nitride from vanadium spinel by synchronous reduction and nitridation with ammonia energy

Summary Ammonia gas (NH 3 ) is a clean energy, as well as an efficient reduction and nitridation agent. A novel process of reduction and nitridation with NH 3 followed by magnetic separation and low-temperature selective chlorination to deal with vanadium slag has been proposed. Vanadium spinel (V-Fe spinel, FeV 2 O 4 ) is the main V-bearing phase in vanadium slag, and its reduction and nitridation behavior with NH 3 were investigated in this study. Thermodynamic analysis indicated that the reaction was feasible. The experimental results demonstrated that NH 3 gas was an excellent reagent for reduction and nitridation. DFT calculation proved that NH 3 molecule was easier adsorbed on V atom. The phase component of the final product was Fe/Fe 4 N/VN x O y , whose relative mass fractions obtained by Rietveld refinement analysis were 23.5%, 1%, and 75.5%, respectively. The evolution of iron and vanadium was in the order FeV 2 O 4 → Fe 4 N/Fe 6 N 2−3 → Fe 4 N/Fe and FeV 2 O 4 → V 2 O 3 → VN x O y , respectively. VN x O y was a solid solution, whose O content decreased gradually as the temperature and duration time increased, whereas the N content increased correspondingly. The O content can be decreased to less than 0.10 wt.% after reduction and nitridation at 800°C to 850°C for 3 h.