Dissolution of ammonium paratungstate tetrahydrate in aqueous ammonia before and after low temperature calcination

Put, John W. van; Duyvesteyn, Willem P.C.; Luger, Floris G.J

doi:10.1016/0304-386x(91)90018-h

Cited by 10 publications

(4 citation statements)

References 16 publications

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“…As illustrated inFig. 6, temperature has little influence on WO3 leaching yield at < 30 o C, whereas increasing temperature reduces the yield at > 30 o C especially with 2 mol/L NH3•H 2O Van Put et al (1991). stated that the amount of dissolved tungsten in aqua ammonia decreases at higher temperatures because of the low boiling point (~36 o C) of NH3•H 2O, which supports the above result.…”

supporting

confidence: 76%

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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supporting

confidence: 76%

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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“…Nevertheless, their investigations were not systematic (no precise powder surface area measurement, no analysis of the solution for the dissolved metal concentration). In the hydrometallurgical extraction literature there are some reports on the chemical dissolution behavior of WO 3 (s) in alkaline solution [18,19]. In contrast, no comparable information is available for acidic solution, although the stability of this oxide in low pH environments is important for CMP as well as other technologically important processes [1][2][3][4][5][6][7][8][9]20].…”

Section: Introductionmentioning

confidence: 99%

Dissolution kinetics of WO3 in acidic solutions

2006

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Potentiostatic polarization and rotating disk electrode techniques were used to obtain the rate constant for the dissolution of electrochemically-formed (at 1 V) WO 3 on tungsten (W) in acidic solutions. The corresponding rate constant for the chemical dissolution of WO 3 (s) powder was found by measuring the dissolved tungsten concentration as a function of time and pH. The chemical dissolution experiments supported the view that the ratedetermining step in the anodic reaction of W in acidic solution is the chemical dissolution of WO 3 (s) formed on the metal surface. Zeta potential measurements gave the isoelectric point (iep) of the WO 3 (s) powder as pH 1.5, a value that was somewhat smaller than the point of zero charge (pzc) of WO 3 (s) formed on W metal (pH 2.5). This difference was attributed to the highly hydrated nature of the oxide film formed on W metal in aqueous systems.

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“…The dissolution of metals from Ag/Cu and Ag/ Au alloys in acidic and cyanide solutions was studied by Choi et al 68 The rate of ammonium paratungstate 85 107 tetrahydrate dissolution in aqueous ammonia was analyzed. 69 Awakura et a!. 70 determined the kinetics of malachite [CU 2 C0 3 (OH)21 dissolution in aqueous ethylenediaminetetraacetate (EDTA) solutions.…”

Section: Hydrometallurgymentioning

confidence: 99%

Developments in physical chemistry and basic principles

Sohn

1992

JOM

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Dissolution of ammonium paratungstate tetrahydrate in aqueous ammonia before and after low temperature calcination

Cited by 10 publications

References 16 publications

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

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

Dissolution kinetics of WO3 in acidic solutions

Developments in physical chemistry and basic principles

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