IRON SEPARATION FROM IRON BEARING POLYMETAL CHLORIDE SOLUTIONS BY
MEANS OF HYDROLYSIS AND CRYSTALLIZATION
B. Nowak, M. Österreicher, J. Pamminger, R. Stastny, H. Weissenbaeck
SMS Siemag Process Technologies, Daffingerstraße 4, 1030 Vienna, Austria
ABSTRACT
The producer of certain metals like Nickel and Cobalt increasingly face a shortage of easy-to-mine and
easy-to-process ore bodies. Their focus is shifting towards alternative raw materials which in turns demand
new, different extraction techniques.
One potential route for processing a ferrous ore with a non-ferrous target metal is atmospheric leaching
with hydrochloric acid, and subsequent separate extraction from the pregnant leach solution (PLS).
For the separation of iron from the PLS, and, in turns, the extraction of the non-ferrous compounds, the
following flow sheet is proposed: Preconcentration of the PLS, oxidation of ferrous (if present) to ferric
chloride, hydrolysis of ferric chloride leading to the precipitation of hematite and evaporation of
hydrochloric acid, followed by crystallization of non-hydrolysable metal chlorides by means of sparging
hydrogen chloride into the solution. Hydrogen chloride required in the latter step is produced internally by
super-azeotropic distillation of regenerated hydrochloric acid. The liquid filtrate from the crystallization
step is recycled to hydrolysis.
Depending on the specific composition of the PLS, the hematite produced contains only traces of other
impurities (typically < 1 wt%), whereas the crystallized mix of non-hydrolysable metal chlorides containing also the target metal in enriched form - contains ferric chloride only in an amount referring to
the filter cake moisture (order of magnitude: 1 wt%). The iron-free crystals can then undergo further
hydrometallurgical separation and extraction processes.
As example, this flow sheet is proposed for treating nickel laterite ores. Experiments related to the
demonstration of crucial assumptions of the flow sheet are presented. Based on those experiments a mass
and energy balance of the flow sheet is estimated and presented together with a table of the major
consumables in order to provide a basis for an estimation of operating cost and process economics.
KEYWORDS
Iron Chloride, Hydrolysis, Nickel Laterite, Hydrochloric acid