Kinetics of Scheelite Conversion in Sulfuric Acid

Shen, Leiting; Li, Xiaobin; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui

doi:10.1007/s11837-018-2787-2

Cited by 20 publications

(3 citation statements)

References 22 publications

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“…When tungsten ore is decomposed in acid solutions, a solid H2WO4 product layer will form on the surfaces of unreacted tungsten mineral particles. It can be dissolved incorporating actions, such as controlling the acid concentration and adding an oxidizing agent [25,26,45]. Due to the absence of thermodynamic data, unfortunately, this paper does not carry out a detailed thermodynamic analysis on tungsten ore decomposition to H2[WO3(C2O4)H2O] and H3PW12O40.…”

Section: In Hcl Solutionsmentioning

confidence: 99%

Thermodynamics of Tungsten Ores Decomposition Process Options

Shen

Taskinen

2018

The Minerals, Metals &Amp; Materials Series

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The thermodynamics of tungsten ore decomposition in mineral acid and alkaline solutions were studied. The published thermodynamic data of tungsten minerals were collected and assessed. The Gibbs energies of CaWO4 (-1538.43 kJ/mol), FeWO4 (-1053.91 kJ/mol), MnWO4 (-1206.08 kJ/mol), H2WO4 (-1003.92 kJ/mol), and Na2WO4 (-1455.58 kJ/mol, aq) at 25 o C were adopted in the calculation using HSC software. The results show that CaWO4 is decomposed more readily in Na2CO3 solution than in NaOH, while FeWO4 and MnWO4 are more reactive in NaOH solutions. From a thermodynamic point of view, tungsten ore decomposes easily in acid solutions despite most ∆ increasing slightly with temperature. Oxidizing Fe 2+ to Fe 3+ in acidic solutions facilitates decomposition of FeWO4, and the reaction of CaWO4 in H2SO4 solution occurs more easily than in other mineral acids, due to the formation of sparsely soluble CaSO4. The results fit well with the experimental data and industrial experience previously reported in the literature.

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Section: In Hcl Solutionsmentioning

confidence: 99%

Thermodynamics of Tungsten Ores Decomposition Process Options

Shen

Taskinen

2018

The Minerals, Metals &Amp; Materials Series

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“…For obtaining pure and high-grade scheelite products for industrial and manufacturing purposes, leaching techniques involving the ore in alkaline media such as sodium carbonate or sodium hydroxide by autoclaving [13][14][15][16] or acidic media such as hydrochloric acid [17,18] or sulfuric acid [19,20] to give tungstic acid (H 2 WO 4 ) are mostly employed. Depending on the source of tungsten ores (wolframite, scheelite, or stolzite), various extraction routes are often used for purifying the leach liquor that arose from the leaching operations.…”

Section: Introductionmentioning

confidence: 99%

Low-Energy Feasibility for Leaching an Indigenous Scheelite Ore for Industrial Applications

Baba

Kayode

Raji

2020

J. Sustain. Metall.

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In recent times, the increasing demand for pure tungsten and its compounds in defense, medicine, high technology, and emerging innovations due to its excellent properties such as its tensile strength, corrosion resistance, and high modulus of elasticity cannot be overemphasized. In this study, an acid leaching route was adopted for the extraction of pure tungsten from a Nigerian scheelite ore consisting primarily of scheelite (Ca 4.00 W 4.00 O 16.00 : 96-900-9627) and quartz (Si 6.00 O 6.00 : 96-900-5019). At optimal leaching conditions (2.5 mol/L HCl, 70 °C, < 75 µm), 88.5% of the initial 10 g/L ore reacted within 120 min. The low apparent activation energy (E a ) estimated as 22.94 kJ/mol with the reaction order of 0.96 affirmed the dissolution reaction to occur through the diffusion control mechanism of the first-order relation. The low E a obtained further supports the feasibility and eco-friendly dissolution process as ⁓11.5% of the undissolved materials analyzed to contain silica (SiO 2 : 96-900-5302) could be used as raw materials for some defined industrial applications.

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“…Considering discharge of high-salinity wastewater, volatility, and cost, sulfuric acid is an appropriate candidate to decompose scheelite concentrate (Forward and Vizsolyi, 1965), forming solid H2WO4 and CaSO4. In our previous work, the conversion of tungsten concentrate in H2SO4 solutions was systematically studied, including the mechanism of H2WO4 layer formation on unreacted tungsten minerals (Li et al, 2017b;Shen et al, 2018a) and the kinetics of scheelite conversion in sulfuric acid (Shen et al, 2018b). It has been approved that tungsten concentrates can be completely converted in H2SO4 solution under appropriate conditions .…”

Section: Introductionmentioning

confidence: 99%

Sustainable and efficient leaching of tungsten in ammoniacal ammonium carbonate solution from the sulfuric acid converted product of scheelite

Shen

Zhou

Peng

et al. 2018

Journal of Cleaner Production

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To directly obtain solution of (NH4)2WO4 instead of Na2WO4 is the key for developing a cleaner technology of ammonium paratungstate production. In this paper, ammoniacal ammon iu m carbonate solution was adopted for leaching tungsten from the converted product, a mixture of H2WO4 and CaSO4 obtained by treating scheelite with sulfuric acid. The research indicates that tungsten can be efficiently extracted in form of ammonium tungstate solution with WO3 leaching yield of > 99.5% under moderate leaching conditions. The WO3 leaching yield is influenced by the transformation of calciu m sulfate to calcium carbonate due to forming CaWO4 through the secondary reaction between CaSO4 and (NH4)2WO4, whereas an excess (NH4)2CO3 (≥ 0.64 mol/L) can suppress the secondary reaction by facilitating the transformation. Additionally, the consumed ammonium carbonate can be recovered by treating the leaching residue with ammonium sulfate solution at above 70 o C. This work presents a cleaner and sustainable technique for producing ammonium paratungstate, with circulating the leaching reagents and bypassing the conversion of Na2WO4 to (NH4)2WO4.

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Kinetics of Scheelite Conversion in Sulfuric Acid

Cited by 20 publications

References 22 publications

Thermodynamics of Tungsten Ores Decomposition Process Options

Thermodynamics of Tungsten Ores Decomposition Process Options

Low-Energy Feasibility for Leaching an Indigenous Scheelite Ore for Industrial Applications

Sustainable and efficient leaching of tungsten in ammoniacal ammonium carbonate solution from the sulfuric acid converted product of scheelite

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