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.