Green one-step roasting method for efficient extraction of vanadium and chromium from vanadium-chromium slag

An effective and environment-friendly method based on one-step sodium hydroxide roasting was proposed to extract vanadium and chromium from vanadium-chromium slag. In optimal conditions (roasting temperature 800 degrees C and NaOH addition dosage 30%), vanadium spinel was converted into NaVO3 while chromium spinel was converted into Na(2)Cra(4) and CaCrO4. Leaching efficiencies of vanadium and chromium reached 94.87% and 80.51%, respectively. During sodium roasting, Na also reacted with Si, Fe, Ti and Al to produce sodium salts of high melting points, which inhibits sintering of reaction mixture and facilitates the formation of vanadates and chromates. The leaching residues consist mainly of Fe2O3, which can be recycled to converter as flux of slagging materials to achieve resource recycling and zero-discharge of solid wastes. This work has provides a simple green way to extract vanadium and chromium from vanadium-chromium slag, which puts forward the green comprehensive utilization of vanadium-titanium magnetite ores with high chromium contents. (C) 2019 Elsevier B.V. All rights reserved.