Solvent extraction of vanadium from a stone coal acidic leach solution using D2EHPA/TBP: Continuous testing

•A continuous tasting of solvent extraction vanadium from a stone coal acidic leach solution using D2EHPA/TBP was studied.•The behaviors of vanadium and common impurities in the extraction process are discussed.•Common impurities in the leach solution can be divided into three groups with respect to their solvent extraction behavior.•High-purity V2O5 (99.61%) was obtained by this process.

This paper reports on continuous testing of a process for the recovery of vanadium from a H2SO4-HF solution, generated from the leaching of stone coal, by solvent extraction using a D2EHPA/TBP mixture as the extractant. Three unit processes are included: fully continuous countercurrent solvent extraction and stripping; oxidation and precipitation; and calcination. The solvent-extraction circuit was operated for 96 h. With six stages of countercurrent extraction, 97.7% vanadium, 98.3% molybdenum, and 97.9% titanium were extracted, while the sodium, potassium, fluorine, and nickel impurities were barely extracted. Scrubbing removed co-extracted and aqueous-entrained zinc, magnesium, silicon, and arsenic impurities. Most co-extracted impurities were scrubbed in two stages. Using five stages of stripping, more than 99.8% of the vanadium was stripped, yielding a vanadium concentration in the loaded strip solution of 34.1 g/L. Co-extracted molybdenum(VI), titanium(IV), and iron(III) remaining in the stripped organic phase were removed by a saturated sodium carbonate solution and the regenerated organic was reused for vanadium extraction. Vanadium was selectively precipitated with 98.5% efficiency from the loaded strip solution by oxidation and precipitation with ammonium sulfate. A high-purity V2O5 (99.61%) product was successfully produced by this flowsheet.