NI43-101Pre-Feasibility Study Report - page 218

Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
, 2014
10135-200-46 - Rev. 0
(<0.5 wt.%). In subsequent tests, calcium was significantly reduced in the REO
High precipitation rate of REEs was attributed to a recycle of oxalate crystals from the
thickener which contained 2.2% – 6.3%TREE. However, calcium content in these
crystals was high and hence lowered the purity of RE oxalate cakes in the main
Overall Recovery
The overall recovery of REEs from COMP E, which was ultimately transferred to a
final oxalate product, feed into a precipitation cake that included 88% Dy, 93% Eu,
94% Nd, 94% Pr, 90% Tb and 79% Y.
Counter –Current Leach
Leach efficiencies of CREEs at steady state conditions ( total acid 434 kg/t, 45
were 89% Dy, 94% Eu, 95% Nd, 95% Pr, 91% Tb and 83% Y. Digestion of REEs was
selective over base metals. Average base metals extractions were 17% Fe, 7% Al,
63% Mg, 46% Mn and 96% Ca.
Overall hydrochloric acid dosage was 401 kg/t. However, actual consumption of fresh
hydrochloric acid was 224 kg/t due to acid recycling. Extraction of REEs increased
with time in the preleach circuit indicating that a longer residence time would be
required (> 4hours) to enhance leach efficiency.
The final leach residue composition averaged 0.57% TREE, 134 g/t Th, 42 g/t U,
7.33% Al, 10.4% Fe, 8.51% K and 23.2% Si, supporting the concept of selective
digestion of REEs over base metals and silica.
Precipitation Cascade
The precipitation campaign for Comp E was limited to a few days and therefore, two
12-hr composite samples were evaluated. Precipitation efficiency of REEs averaged
95% but, steady state precipitation efficiencies of CREEs ( Total 82 g/L oxalate
dosage) were 99% Dy, 99% Eu, 99% Nd, 98% Pr, 99% Tb and 95% Y. Thorium
precipitation was 100%.
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