Leaching of vanadium from chromium residue

Abstract A chromium residue containing 4.8% V 2 O 5 and 30.2% Cr was obtained from a wastewater treatment plant. The leaching of vanadium from this residue using H 2 SO 4 , NaOH or Na 2 CO 3 was trialled. Different pretreatments including rinse, direct roasting and rinse followed by roasting were studied for their effects on vanadium extraction. It was found that a water rinse enhanced alkaline leaching of vanadium but not acidic leaching. The leaching efficiency of V 2 O 5 was satisfactory when roasted residue was leached by H 2 SO 4 , but some gaseous pollutants such as Cl 2 , HCl, and SO 2 , were produced when the residue was roasted at 800 °C. Leaching by NaOH extracted more vanadium than by Na 2 CO 3 . Vanadium extraction was adversely affected by oxidation of excess H 2 O 2 , while using KClO 3 improved the extent of V 2 O 5 leaching by NaOH. After being rinsed and oxidized by 2% KClO 3 , the residue was leached by 30% NaOH with a liquid–solid ratio of 2:1 in a stirred flask for 1 h at 95 °C, and the V 2 O 5 leaching efficiency could reach up to 85%.