A Novel Method of Recovery Vanadium from Vanadium Slag through CaO2-Briquetting Roasting Process

This study proposes a clean and effective routine and aims to solve the problems of material accumulation and hypoxia during roasting vanadium slag. The vanadium slag and CaO 2 powders are mixed, briquetted, and roasted at different parameters. The generated phases are Fe 2 O 3 , Fe–Mg oxides, Fe–Ti oxides, Ca 3 (VO 4 ) 2 , silicate, and SiO 2 after roasting. The solid reaction between V 2 O 5 and CaO is described using the vacancy diffusion mechanism. Ca 2+ (or V 5+ ) jumps and diffuses through the Ca 2+ (or V 5+ ) vacancies in the Ca 3 (VO 4 ) 2 layer and subsequently to the Ca 3 (VO 4 ) 2 /V 2 O 5 (or Ca 3 (VO 4 ) 2 /CaO) interface and reacts with V 2 O 5 (or CaO) and O 2 (decomposed from CaO 2 or transported from the air) to generate Ca 3 (VO 4 ) 2 . The vanadium leaching rate is very sensitive to the roasting parameters of CaO/V 2 O 5 molar ratio, temperature, time, and briquetting pressure. A maximum vanadium leaching rate of 98.31% is achieved with a CaO/V 2 O 5 molar ratio of 3/1, with temperature, time, and briquetting pressure being maintained at 900 °C, 50 min, and 10 MPa, respectively. The present routine, which greatly shortens the roasting time, can be realized through a rotary hearth furnace, and is likely to be accepted by both iron works and the environment due to its effective and clean characteristics.