Extraction and separation of vanadium (IV) by EHEHPA with citric acid complexing iron (III) from sulfate leaching solution

Abstract

The recovery of vanadium from sulfate leaching solutions is crucial for resource sustainability and environmental protection. However, the leaching solution contains impurities such as Fe (III), which have a significant impact on the separation and enrichment of V because a) the separation of Fe (III) and V (IV) through solvent extraction is problematic, and b) in the presence of oxygen from the air, it is challenging to fully reduce Fe (III) to Fe (II). Citric acid was used as a complexing agent in the aqueous phase to complex the Fe (III), and the effect of V (IV) extraction using 2-Ethylhexylphosphoric acid mono-2-ethylhexyl ester (EHEHPA) after Fe (III) complexation was investigated. To determine the complexation dose necessary for complete Fe (III) complexation, the numbers of ligands in the citric acid and Fe (III) complex were estimated, and the complexation mechanism of citric acid with Fe (III) was further clarified using UV–vis and FT-IR. According to the experimental findings, citric acid exhibits better complexing action than other complexing agents. Citric acid may complex > 96 % of Fe (III) in the liquid phase when the molar ratio of citric acid to Fe (III) is 1.5. When the pH of the solution was 1.2 and the molar ratio of citric acid to Fe (III) was 2, the extraction rates of V (IV) and Fe (III) obtained through EHEHPA were > 80 % and < 1 %, respectively. Additionally, the maximum separation factor βV/Fe was 430, which helped achieve the complete removal of Fe (III).