Sustainable and efficient leaching of tungsten in ammoniacal ammonium carbonate solution from the sulfuric acid converted product of scheelite. (1st October 2018)

• Record Type: Journal Article
• Authors: Shen, Leiting; Li, Xiaobin; Zhou, Qiusheng; Peng, Zhihong; Liu, Guihua; Qi, Tiangui; Taskinen, Pekka
• Is Part Of: Journal of cleaner production. Volume 197(2018)Part 1
• Page Start: 690
• Page End: 698
• Publication Date: 2018-10-01
• Subjects: Tungstic acid -- Calcium sulfate -- Leaching mechanism -- Calcium carbonate -- Ammonium paratungstate; Factory and trade waste -- Management -- Periodicals; Manufactures -- Environmental aspects -- Periodicals; Déchets industriels -- Gestion -- Périodiques; Usines -- Aspect de l'environnement -- Périodiques; 628.5
• DOI: 10.1016/j.jclepro.2018.06.256
• Languages: English
• ISSNs: 0959-6526

Abstract

Abstract: To directly obtain solution of (NH4 )2 WO4 instead of Na2 WO4 is the key for developing a cleaner technology of ammonium paratungstate production. In this paper, ammoniacal ammonium carbonate solution was adopted for leaching tungsten from the converted product, a mixture of H2 WO4 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 calcium sulfate to calcium carbonate due to forming CaWO4 through the secondary reaction between CaSO4 and (NH4 )2 WO4, whereas an excess (NH4 )2 CO3 (≥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 °C. This work presents a cleaner and sustainable technique for producing ammonium paratungstate, with circulating the leaching reagents and bypassing the conversion of Na2 WO4 to (NH4 )2 WO4 . Highlights: Tungsten was efficiently extracted from the mixtures of H2 WO4 and CaSO4 using ammoniacal (NH4 )2 CO3 . The conversion of CaSO4 to CaCO3 influences the WO3 leaching efficiency. (NH4 )2 CO3 can restrain the secondary reaction of CaSO4 with (NH4 )2 WO4 . Consumed ammonium carbonate can be recovered by heating (NH4 )2 SO4 solution with leaching residue.