Acidic leaching of scheelite concentrate and production of hetero-poly-tungstate salt

The aim of this study is to investigate the utility of adding chelating age nt during hydrochloric acid leaching of low-grade scheelite concentrates, o btained from Uludag, Bursa (Turkiye). Examined parameters were as follows; leaching conditions, selective precipitation of tungsten salt from the acid ic leach solution in which tungsten exists as hetero-poly-tungstate, the op timum precipitation conditions, the possibility of obtaining pure and nano- sized tungsten salt. Chelating agent leaching of scheelite concentrates in acidic solutions involves fewer process steps as compared to the classical methods. Furthermore, this route enables production of pure WO3 under preva lent conditions and without generating any spent liquor. The optimum leachi ng conditions were found to be 80 degrees C, 2 M HCl, 1/10 solid/liquid rat io, stirring speed of 900 min(-1) and W/PO43- weight ratio of 7/1. A tungst en leaching efficiency of 98% was reached under these conditions. It was al so possible to selectively precipitate a pure (over 99%) tungstate salt, wi thin minutes, from the poly-tungstate solution at 25 degrees C by adding a 'chelate breaking agent' at a NH4+/WO3 weight ratio of greater than or equa l to 1/4. (C) 1999 Published by Elsevier Science B.V. All rights reserved.