Effect of mechanical activation on extraction of vanadium from chromium-containing vanadate solution by calcification and carbonization

Abstract

The effect of mechanical activation on extraction of vanadium from chromium-containing vanadate solution by precipitation with calcium salt and leaching with sodium carbonate salt was investigated. The whole process including selective precipitation of vanadium, alkali leaching of vanadium and cyclic utilization of calcium. Compared with stirring, ball milling is more effective for vanadium precipitation under the same experiment conditions. This is because the calcium vanadate formed on the surface of Ca(OH)2 can be peeled off by mechanical activation, which can also be confirmed by SEM image, EDS spectra and XRD patterns of the precipitation. The effect of temperature ranging from 20 °C to 50 °C on vanadium leaching efficiency was studied with the other reaction conditions fixed as stirring speed of 400 r/min, NaHCO3/V molar ratio of 2.80, L/S ratio of 4:1 ml/g. It is observed that vanadium leaching efficiency exceeding 99% was obtained after only 6 min of reaction as well as leaching temperature had little influence on vanadium leaching efficiency. After filtration, the leach solution was used to prepare crystals of NH4VO3 and the leach residue was calcined to obtain CaO. The precipitation efficiency of V was 99.34% by adding CaO into chromium-containing vanadate solution according to Ca/V molar ratio 1.80 and ball milling for 90 min with 140 rpm at room temperature. Mechanical activation can not only increase the vanadium precipitation efficiency and improve the leaching performance of the precipitate, but also to realize the cyclic utilization of calcium salt and crystallization solution.