Abstract
The recovery of vanadium from a typical low-grade refractory stone coal was investigated using a pyro-hydrometallurgical process specifically including blank roasting, acid leaching, solvent extraction, and chemical precipitation. The appropriate role of parameters in each process was analyzed in detail. Roasting temperature and roasting time during the roasting process showed a significant effect on leaching efficiency of vanadium. Using H2SO4 as a leaching agent, vanadium leaching efficiency can achieve above 90% under the optimum leaching conditions of CaF2 dosage of 5%, sulfuric acid concentration of 4 mol/L, liquid to solid ratio of 2:1 mL/g, leaching time of 2 h, and leaching temperature of 95 °C. 99.10% of vanadium can be extracted from the leaching solution in three stages under the conditions of initial pH of 1.6, trioctylamine (TOA) extractant concentration of 20% (vol), phase ratio (A/O) of 2, and reaction time of 2 min. 1.0 mol/L NaOH was used to strip vanadium from the extracted solvent phase. After purification and precipitation, vanadium can be crystallized as ammonium metavanadate. The V2O5 product with a purity of 99.75% is obtained after ammonium metavanadate thermal decomposition at 550 °C for 2 h. The total vanadium recovery in the whole process is above 88%. This process has advantages of short operation time, high vanadium extraction efficiency, and high purity of the product.
Highlights
Vanadium plays an important role in many fields because of its special properties in hardness, high tensile strength, excellent corrosion resistance at low temperature, and specific physiological functions [1]
The XRD (X-ray diffraction) pattern of raw ore (Figure 1) revealed that the main mineral compositions were quartz, pyrite, calcite, Chemical compositions of stone coal were shown in Table 1, the content of V2 O5 in the raw ore and muscovite
The results showed that pH had a great effect on vanadium extraction as the extraction efficiency increased from 16% to 93% when the pH increased from 0.0 to 1.6
Summary
Vanadium plays an important role in many fields because of its special properties in hardness, high tensile strength, excellent corrosion resistance at low temperature, and specific physiological functions [1]. In China, stone coal is a special vanadium-bearing resource that contains enormous reserves of vanadium. Stone coal is a kind of carbonaceous shale which looks like coal but mostly consists of quartz and with a low calorific value [2]. Vanadium in stone coal exists in the isomorphism-like form in which vanadium replaces trivalent aluminum in the mica structure [3]. The mica structure is stable, so the key step of extracting vanadium from vanadium-containing mica is to destroy the lattice structure of the mica. Roasting and acid leaching are the most effective ways to destroy the lattice structure of mica [4]. To recover vanadium from stone coal, it is usually treated through several procedures, such as roasting, leaching, purification, and precipitation [5,6]
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