Abstract
The recovery of vanadium from sulfuric and hydrofluoric mixed acid solutions generated by the direct leaching of black shale was investigated using solvent extraction and precipitation methods. The process consisted of reduction, solvent extraction, and stripping, followed by precipitation and calcination to yield vanadium pentoxide. The influence of various operating parameters on the extraction and recovery of vanadium was studied. Vanadium (IV) was selectively extracted using a mixture of 10% (v/v) di(2-ethylhexyl)phosphoric acid and 5% (v/v) tri-n-butylphosphate in sulfonated kerosene. Using six extraction and five stripping stages, the extraction efficiency for vanadium was 96.7% and the stripping efficiency was 99.7%. V2O5 with a purity of 99.52% was obtained by oxidation of the loaded strip solution and precipitation of ammonium polyvanadate at pH 1.8 to 2.2, followed by calcination of the dried precipitate at 550 °C for 2 h. It was concluded that the combination of solvent extraction and precipitation is an efficient method for the recovery of vanadium from a multi-element leach solution generated from black shale.
Highlights
Black shale is an important vanadium resource in China, where it is found extensively in the southern provinces and autonomous regions of the country
This study provides data to develop a flow sheet for the recovery of a high purity vanadium product from the solutions generated by the direct leaching of black shale
The results show that vanadium extraction efficiency initially increases with increasing pH because this is a cation exchange process
Summary
Black shale ( called stone coal) is an important vanadium resource in China, where it is found extensively in the southern provinces and autonomous regions of the country. The gross reserves of vanadium in black shale in Hunan, Hubei, Guangxi, Jiangxi, Zhejiang, Anhui, Guizhou, Henan, and Shanxi provinces are 18 million tons in terms of V2 O5 , which accounts for more than 87% of the domestic reserves of vanadium [1]. The vanadium grade in black shale generally ranges from. 0.13% to 1.2%, while grades higher than a cut-off of 0.5% account for about 40% of the total vanadium reserves [2]. Black shale is regarded as a complicated low-grade multi-element ore. Because of its relatively high vanadium grade and abundant deposits, studies of the recovery of vanadium from black shale have received considerable attention
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