Clean production technology for effective recovery of vanadium from shale: Interaction between activators and vanadium-loaded minerals

Abstract

The vanadium in shale is embedded in the muscovite crystal phase, hindering its solubility in leaching process. In this study, a pre-decarburization activated roasting and mild acid leaching process was developed for the recovery of vanadium from shale. The results showed that NaCO3 and K2SO4 were the most effective composite additives to break muscovite into microcline and promote the production of water-soluble vanadate. Thermodynamic analysis exhibited that the pre-decarbonization before roasting was beneficial to the full oxidation of vanadium, and confirmed that the addition of K2SO4 in roasting prevented the formation of insoluble calcium vanadate, but produced anhydrite instead. XRD and SEM-EDS analysis verified that the formations of microcline and anhydrite hindered those of anorthite and calcium vanadate, and it enhanced the leaching efficiency of vanadium to 92% under the condition of mild acid leaching (2% v/v H2SO4 only). This process significantly promoted the amount of water-soluble vanadium so as to reduce the acid consumption in leaching and the content of impurities (i.e., Fe3+, Fe2+). Finally, V2O5 with purity of 99.5% was obtained after ion exchange with resin D201, precipitation by acid ammonium salt and calcination.