Efficient Separation and Extraction of Vanadium and Chromium in High Chromium Vanadium Slag by Selective Two-Stage Roast
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VANADIUM, chromium, and their compounds are important rare metal resources, and are generally used in various fields such as steel alloys, ceramics, catalysts, and so on.[1–4] Furthermore, the toxicity and carcinogenicity of high valence vanadium (V) and chromium (VI)[5,6] are another important reasons why they are widely concerned. In China, the main feedstock for vanadium extraction is vanadium–titanium-bearing magnetite, a complicated ore including iron, vanadium, titanium as well as other valuable elements such as chromium. During smelting with vanadium–titanium-bearing magnetite, chromium and vanadium with similar chemical properties are reduced into the molten pig iron with coke in a blast furnace and then oxidized
TAO JIANG and XIANGXIN XUE are with the School of Metallurgy, Northeastern University, and the Liaoning Key Laboratory for Recycling Science of Metallurgical Resources, Shenyang, 110819, Liaoning, China. JING WEN, YINGZHE XU, and JIAYI LIU are with the School of Metallurgy, Northeastern University. Contact e-mail: [email protected] Manuscript submitted September 25, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
and enriched into the vanadium slag in a vanadium-extracting converter. In the traditional vanadium extraction processes, chromium is removed as a kind of impurity.[7,8] While for HCVS, chromium can no longer be ignored due to its comparable content with vanadium, and HCVS could be regarded as a potential feedstock to extract vanadium and chromium simultaneously. The immature research of co-extracting vanadium and chromium efficiently with lower cost, along with the toxicity of chromium hinder the utilization of HCVS in industry, and the most remarkable obstacle is the separation technology of vanadium and chromium. At present, sodium salt roasting is the most commonly used technology for vanadium extraction from ordinary vanadium slag with lower chromium,[8] which includes the separation process of vanadium and chromium in the liquid phase. Many works have reported that chromium (III) can be oxidized to soluble sodium chromate (VI) and transfer into liquor phase along with sodium vanadate.[9] Various methods to separate vanadium and chromium in the liquid phase emerge such as chemical precipitation,[10] solvent extraction,[11–14] ion exchange,[15] and adsorption.[16] The chemical precipitation methods were limited due to the low purification of products and the high consumption of acid.[13] The solvent extraction methods had high cost and complex processes, hindering the
large-scale application in the actual industrial production. And the ion-exchange methods produced large volume of wastewater. Therefore, it is meaningful to investigate a new low-cost and simple process for separating and extracting vanadium and chromium in HCVS. Meanwhile, it is worth noting that most of the existing separation techniques have focused on the extraction of vanadium and chromium in the liquid phase after leaching stage, but little for the separation at the roasting stage, which would be a complete
