Research progress of vanadium extraction processes from vanadium slag: A review

Vanadium slag contains valuable elements vanadium and chromium. The purpose of this paper is to review the research progress of vanadium extraction processes. The elements content, phase composition and elements distribution of vanadium slag are summarized. According to the variation of the valence state of vanadium in the vanadium extraction processes, the research progress of different vanadium extraction technologies is systematically summarized. The extraction of element vanadium is calculated thermodynamically. The advantages and disadvantages of different vanadium extraction techniques, which are reduction (direct alloying and direct smelting of FeV), original valence extraction (molten salt chlorination), and oxidation (sodiumization, calcification, sub-molten salt, blank roasting, direct acid immersion, oxidative chlorination) are expounded. Oxidation treatment technologies are widely used at present, which can effectively extract vanadium in vanadium slag and prepare vanadium oxide. Although the processes of extracting vanadium by oxidation roasting have the problems of waste water, waste residue and waste gas, it is still the main process at present. The extraction of vanadium in the original valence state is only in the laboratory stage and further verification is needed. The reduction method has been verified in industry while the problems such as impurity elements and high energy consumption need to be further solved. The extraction of vanadium is in urgent need of further development of clean and green technology.