A cleaner method featuring non-salt roasting and ammonium bicarbonate leaching has been studied for the extraction of vanadium from vanadium slag. Compared to the traditional alkaline salt roasting followed by water leaching process, chromium spinel in the raw vanadium slag will not be converted to carcinogenic chromate salts and exhaust gas will not be produced in the non-salt roasting process. The soluble salt, NH4VO3, can be easily crystallized directly by cooling. The wastewater from vanadate precipitation can be recycled in the leaching process. The leaching residue can be comprehensively utilized in conjunction with an iron-making process. The oxidation mechanisms of vanadium spinel were analyzed using XRD and SEM-EDS. Additionally, the effects of leaching variables, including ammonium bicarbonate concentration, roasted vanadium slag particle size, and leaching temperature, were examined. Finally, the leaching thermodynamics and leaching kinetics have been studied. (C) 2017 Elsevier Ltd. All rights reserved.