Extraction of vanadium(V) from a vanadium-bearing shale leachate through bifunctional coordination in Mextral 984H extraction system

The sulfuric acid leachate from vanadium-bearing shale (SALV) has high acidity with pH around 0.5, and contains several different elements. The chelating extractant Mextral 984H was proposed to extract vanadium from said leachate. In this study, the effects of pH, temperature, extraction time, phase ratio and Mextral 984H concentration on the vanadium extraction efficiency were investigated. Moreover, this has been appraised as well in regards to other impurities such as iron, aluminum, magnesium, potassium, phosphorus, and calcium. The results show that 99.55% of vanadium was extracted through a three-stage extraction, while concentration of extracted impurities was lower than 3%. These experiments were carried out at pH = 0.53, temperature of 25℃, extraction time of 12 min, phase ratio (A/O) equal to 2:1, Mextral 984H concentration of 20 vol% and sulfonated kerosene as diluent. The extraction mechanism of vanadium was investigated using FT-IR, 1H NMR, ESI and quantitative calculations. It has been observed that the O atom on the phenolic hydroxyl and the N atom on the oximido were coordinated with V(V) to form an extraction complex composed of a six-membered ring with 1:1 (metal:ligand) mole ratio; interestingly, the H atom on the phenolic hydroxyl was dissociated. According to the reported results, the Mextral 984H extraction system can be used to extract vanadium from the SALV with no need to adjust pH, which can simplify the extraction process and reduce the consumption of chemicals.