Kinetics of the Carbonate Leaching for Calcium Metavanadate

The sodium salt roasting process was widely used for extracting vanadium due to its high yield rate of vanadium. However, the serious pollution was a problem. The calcium roasting process was environmentally friendly, but the yield rate of vanadium was relatively lower. Focusing on the calcium metavanadate produced in the calcium roasting process of vanadium minerals, the mechanism of the carbonate leaching for calcium metavanadate and its leaching kinetics of calcium metavanadate were studied. With the increase of the leaching agent content, the decrease of the particle size, the increase of the temperature and the increase of the reaction time, the leaching rate of vanadium increased, and the constant of reaction rate increased. In the carbonate leaching process, the calcium carbonate was globular and attached to the surface of calcium metavanadate. In the solution containing bicarbonate radical, lots of cracks formed in the dissolution process. However, the cracks were relatively fewer in the solution containing carbonate. In the present study, the carbonate leaching for calcium metavanadate was controlled by diffusion, the activation energy reached maximum and minimum in the sodium bicarbonate and the sodium carbonate solution, respectively. The activation energy value in the ammonium bicarbonate solution was between those two solutions. The kinetic equations of the carbonate leaching for calcium metavanadate were as follows: 1 - 2/3 eta- (1-eta )(2/3) = 4.39[Na2CO3](0.75)/r(0) x exp(-2527.06/T)t; 1 - 2/3 eta- (1-eta )(2/3) = 7.89[NaHCO3](0.53)/r(0) x exp(-2530.67/T)t; 1 - 2/3 eta- (1-eta )(2/3) = 6.78[NH4HCO3](0.69)/r(0) x exp(-2459.71/T)t.