Selective vanadium extraction from vanadium bearing ferro-phosphorus via roasting and pressure hydrogen reduction

A novel process involving roasting with additives, water leaching, and vanadium precipitation by high-pressure hydrogen reduction is proposed to selectively extract vanadium from vanadium-bearing ferro-phosphorus. The optimum conditions of roasting and leaching are obtained as follows: roasting temperature of 850 degrees C, Na2CO3 dosage of 30 wt%, CaCO3 dosage of 30 wt%, roasting time of 1 h, leaching time of 2 h and a leaching liquid-solid ratio of 1 mL/g. A V2O3 product having a purity of 99.92% is precipitated from the leaching solution by a high-pressure hydrogen reduction. The total recovered vanadium is up to 92.3%. X-ray diffraction (XRD) analysis of the raw ore, roasted ore, and leaching residue shows that the additive of Na2CO3 during roasting can react with the vanadium-bearing compounds and transform it into water-soluble NaVO3, while the additive of CaCO3 can solidify phosphorus-bearing and chromium-bearing compounds into non-water-soluble phosphates of Ca-3(PO4)(2) and Cr-3(PO4)(2). Moreover, the iron-bearing compounds are converted into non-water-soluble Fe2O3 and Na3Fe2(PO4)(3). Thus, vanadium can be selectively extracted through the subsequent water leaching and high pressure hydrogen reduction process. Compared with the traditional process, this process is more efficient and environmentally friendly owing to the high recovery of vanadium, the non-used roasting additive of sodium chloride and the adopted eco-friendly vanadium precipitation method.