Effect of CaF2/CaO Composite Additive on Roasting of Vanadium-Bearing Stone Coal and Acid Leaching Kinetics

et al. 2018

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Abstract:In this paper, potassium salt roasting additives were applied to extract vanadium from vanadium-titanium magnetite concentrate. Meanwhile, the mechanisms of potassium salt roasting and acid leaching kinetics were investigated. The results indicate that potassium salt roasting additives are more efficient than sodium and calcium salt and that K 2 SO 4 works best. Under certain conditions (a dosage of K 2 SO 4 of 4 wt %, a roasting temperature of 900 • C, a roasting time of 1 h, a leaching temperature of 95 • C, a sulfuric acid concentration of 10% (v/v), and a leaching time of 1.5 h with a liquid to solid ratio of 3 mL/g) the vanadium leaching efficiency reached 71.37%, an increase of 30.20% compared to that of blank roasting. Additionally, XRD and related SEM-EDS analyses indicated that K 2 SO 4 fully destroyed the structure of vanadium-bearing minerals such as magnetite, and promoted the generation of soluble KVO 3 to inhibit the formation of insoluble Ca(VO 3 ) 2 in the roasting process. Furthermore, it promoted the dissolution of sphene and the release of its vanadium in the leaching process, which increased the vanadium leaching efficiency significantly. Meanwhile, leaching kinetics analyses showed that the leaching process was controlled by internal diffusion; the apparent activation energy decreased from 37.43 kJ/mol with blank roasting to 26.31 kJ/mol with potassium salt roasting. The reaction order, with regards to the sulfuric acid concentration, decreased from 0.6588 to 0.5799. Therefore, potassium salt roasting could improve mineral activity, accelerating the leaching process and reducing the dependence on high temperature and high acidity.

Section: Effect Of Different Additives and Their Dosage On The Vanadimentioning

confidence: 91%

Section: Kinetics Analyses Of Vanadic Acid Leaching Processmentioning

confidence: 99%

Efficient Extraction of Vanadium from Vanadium–Titanium Magnetite Concentrate by Potassium Salt Roasting Additives

Liu

et al. 2018

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“…Vanadium has been widely used in defense-related, aerospace, chemical industry, medicine, advanced materials, and other high-tech fields due to its unique physical and chemical properties [1][2][3][4][5][6]. In China vanadium-bearing shale is a dominant vanadium resource, and more than 87% of the vanadium exists in this unique vanadium resource [7][8][9]. Therefore, vanadium extraction from vanadium-bearing shale has been attracting enormous attention recently [10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

The Effects of Sodium Ions, Phosphorus, and Silicon on the Eco-Friendly Process of Vanadium Precipitation by Hydrothermal Hydrogen Reduction

Bao

2018

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The effects of sodium ions, phosphorus, and silicon on the eco-friendly process of vanadium precipitation by hydrothermal hydrogen reduction were investigated to establish the suitable concentrated solution system for this eco-friendly process. The results showed that sodium ions had no negative effects on the vanadium precipitation process. Phosphorus can reduce vanadate ion activity, and results in the decrease of vanadium precipitation percentage from 99.5% to 61.3%, as the phosphorus concentration in the feed solution increased from 0.05 g/L to 3 g/L. As a result, the aimed products of V 2 O 3 were hard to be obtained, and the purity of the precipitates was lowered. Silicon can absorb in the form of H 3 Si 3 O 7 on the surface of the precipitates, thus it was difficult for H (activity hydrogen atom) to react with the intermediate vanadium-bearing precipitates. As a result, the vanadium precipitation percentage decreased from 99.5% to 86.2% as the silicon concentration in the feed solution increased from 0.1 g/L to 3 g/L. The aimed products of V 2 O 3 were not easy to be obtained, and only the intermediate vanadium-bearing precipitates containing sodium ions were obtained. The upper limits of the concentrations of phosphorus and silicon in the feed V (V) solution were ascertained as 0.5 g/L and 0.1 g/L, respectively. As the concentrations of phosphorus and silicon in the purified alkaline-concentrated V (V) solution extracted from vanadium-bearing shale are usually below the upper limits of the concentrations, the eco-friendly process of vanadium precipitation by hydrothermal hydrogen reduction has a great application prospect in the field of vanadium extraction from vanadium-bearing shale.At present, vanadium precipitation is an indispensable process for vanadium extraction from vanadium-bearing shale [7]. The most popular vanadium precipitation method is vanadium precipitation with ammonium salt, due to its high recovery of vanadium and high purity of the obtained vanadium products [7,[17][18][19]. But this process can cause serious water and air pollution due to the addition of a large amount of ammonium salt. This environmental problem has become one of the most important factors restricting the green and sustainable development of the vanadium extraction industry.In order to solve the environmental problem in the present vanadium extraction process, an eco-friendly vanadium precipitation process without the addition of ammonium salt has been developed and reported in our previous study [20]. In this eco-friendly process, the hydrothermal hydrogen reduction technology was used for precipitating V 2 O 3 products from the stripped pentavalent vanadium (V (V)) solution extracted from vanadium-bearing shale. Both of the vanadium precipitation efficiency and the purity of the products can reach more than 99%. However, the contents of the impurity elements, such as phosphorus and silicon, in the stripped vanadium solution were very low, which cannot represent all the concentrated vanadium solutions obtained from...

“…Thus, there is still a great possibility of improving the vanadium leaching efficiency. Generally, compared to a single additive, composite additives have been considered to work better in extracting vanadium due to the synergistic effect [14,21]. Furthermore, the deeper mechanism of vanadium extraction needs to be explained, such as the essence of vanadium extraction with roasting and the rule of vanadium migration and transformation.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Novel K2SO4/KCl Composite Roasting Additive for Strengthening Vanadium Extraction from Vanadium–Titanium Magnetite Concentrate

Liu

et al. 2018

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In this paper, a novel K2SO4/KCl composite roasting additive was used to extract vanadium from vanadium–titanium magnetite concentrate. Further, the mechanism of K2SO4/KCl for extracting vanadium was studied. The results indicate that the vanadium leaching efficiency reached 82.04%, an increase of 7.43% compared to that of single K2SO4 and 10.05% compared to single KCl under the following conditions: a total dosage of K2SO4/KCl of 7 wt % with a mass ratio of 6/4, a roasting temperature of 950 °C, a roasting time of 1 h, a leaching temperature of 95 °C, a sulfuric acid concentration of 10% (v/v: volume percentage), and a leaching time of 1.5 h with a liquid-to-solid ratio of 3 mL/g. Moreover, crystal chemistry analyses indicated that the essence of the vanadium extraction with roasting was the conversion of cubic crystal systemic vanadium-bearing magnetite (FeO(Fe,V)2O3) to trigonal crystal systemic hematite (α-Fe2O3), and as most Fe(V)–O bonds were broken with the reconstructed conversion, the dissociation of V(III) occurred. Furthermore, the main decomposition products of K2SO4/KCl were K2O, SO2, and Cl2. X-ray diffraction (XRD) and related SEM-EDS analyses indicated that there were mainly three aspects in the mechanism of K2SO4/KCl for extracting vanadium. Firstly, activated K2O could combine with vanadium to generate soluble KVO3 rather insoluble Ca(VO3)2; secondly, SO2 could react with CaO to form CaSO4 to prevent the generation of acid-consuming Ca(VO3)2, which was beneficial to the dissolution of vanadium-bearing sphene (Ca(Ti,V)SiO4O); thirdly, Cl2 could destroy the structure of hematite (Fe2O3) to reduce its wrapping extent to KVO3.