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

No Thumbnail Available
Journal Title
Journal ISSN
Volume Title
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2018-10-01
Major/Subject
Mcode
Degree programme
Language
en
Pages
9
690-698
Series
JOURNAL OF CLEANER PRODUCTION, Volume 197
Abstract
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 ammonium 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 calcium 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 °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.
Description
Keywords
Ammonium paratungstate, Calcium carbonate, Calcium sulfate, Leaching mechanism, Tungstic acid
Other note
Citation
Shen , L , Li , X , Zhou , Q , Peng , Z , Liu , G , Qi , T & Taskinen , P 2018 , ' Sustainable and efficient leaching of tungsten in ammoniacal ammonium carbonate solution from the sulfuric acid converted product of scheelite ' , Journal of Cleaner Production , vol. 197 , pp. 690-698 . https://doi.org/10.1016/j.jclepro.2018.06.256