Effects of different alkalis on the behaviour of vanadium loss in the pretreatment of vanadium-bearing acid leaching solution

Abstract

This study examined the effect of different pretreating agents on vanadium loss from vanadium-bearing shale. Acid leaching solutions with added Ca(OH) 2 , CaCO 3 , NaOH, Na 2 CO 3 , and ammonia solution were evaluated. The pH of the acid leaching solution was adjusted to 2.0 to reduce vanadium loss and allow efficient removal of impurities, providing a high vanadium extraction efficiency. Ca(OH) 2 was the most effective neutralizer and its use resulted in a vanadium loss rate was as low as 4%. SEM-EDS analysis indicates that a major cause of vanadium loss is entrapment and absorption by precipitates. The low vanadium loss rate using Ca(OH) 2 as a neutralizer appears to be due to the smooth and flat surface of the precipitate, which limits vanadium entrainment. When the pH was adjusted with CaCO 3 , the crystal structure of the precipitate was incomplete. In addition, CaSO 4 and iron phosphate particles interact, promoting entrainment and absorption of vanadium. Similarly, flocculent iron phosphate was generated when the pH was adjusted with NaOH, Na 2 CO 3 , or ammonia, resulting in a crystal with a rough surface that easily entrained vanadium.