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

Abstract

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 CaO2 powders are mixed, briquetted, and roasted at different parameters. The generated phases are Fe2O3, Fe–Mg oxides, Fe–Ti oxides, Ca3(VO4)2, silicate, and SiO2 after roasting. The solid reaction between V2O5 and CaO is described using the vacancy diffusion mechanism. Ca2+ (or V5+) jumps and diffuses through the Ca2+ (or V5+) vacancies in the Ca3(VO4)2 layer and subsequently to the Ca3(VO4)2/V2O5 (or Ca3(VO4)2/CaO) interface and reacts with V2O5 (or CaO) and O2 (decomposed from CaO2 or transported from the air) to generate Ca3(VO4)2. The vanadium leaching rate is very sensitive to the roasting parameters of CaO/V2O5 molar ratio, temperature, time, and briquetting pressure. A maximum vanadium leaching rate of 98.31% is achieved with a CaO/V2O5 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.