New calcification roasting–sulfuric acid leaching：A zero-discharge, cleaner-sustainable and multi-value-added products route of vanadium

A clean and efficient route for extraction of vanadium from vanadium slag by electro-oxidation combined with ultrasound cavitation

“…Fig. 10 (d) shows that the characteristic absorption peaks observed at 600 nm and 768 nm are related to V 3+ and VO 2+ , respectively [9] , [49] . This indicates that the obtained leachates were mixtures of V 3+ ion and VO 2+ ion.…”

“…This may be attributed to that the Fe 3+ /Fe 2+ has a high electrode potential. The leached V 3+ ion could be chemically oxidized to VO 2+ ion by Fe 3+ ion as describing by equation (2) [9] . Fe 3+ + V 3+ + O 2– → Fe 2+ + VO 2+ …”

“…V mainly exists in insoluble spinel as V(III) in VS [6] . Several methods have been developed to extract V from VS including sodium salt roasting-water/acidic leaching [7] , [8] , calcification/lime roasting-acidic leaching [9] , [10] , [11] , non-salt roasting-acidic leaching [12] , manganese roasting-acidic leaching [13] , etc. By roasting at high temperature in air atmosphere, the V(III) in spinel can be fully oxidized, converting stable spinel into the leachable forms such as NaVO 3 , Na 4 V 2 O 7 , CaV 2 O 6 , etc.…”