NI43-101Pre-Feasibility Study Report - page 219

Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
, 2014
10135-200-46 - Rev. 0
Selective oxalate precipitation of REE was exceptionally better during this campaign.
The average oxalic acid dosage was 85 g/L, but the actual consumption of fresh
oxalic acid was 40.7 g/L equivalent to 175 kg/t concentrate due to recycle of oxalates.
A combined residence time of 2.3 hours was sufficient to precipitate REEs selectively
at elevated temperature ( 85-95
C) and high acid strength.
The RE oxalate precipitates contained 36.9% TREE, 37.4% oxalate, 2980 g/t Th and
only 0.58% Ca.
The captured RE oxalates from the post-precipitation circuit for recycling contained
25% TREE, 34.8% oxalate, 491 g/t Th and 5.9% Ca with traces of base metals (<
Overall Recovery
This composite represents the feed ore in years 1-9 of the Life of Mine (LoM).
Overall recoveries of REEs from ore to oxalate precipitate cake included 84% Dy,
88% Eu, 88% Nd, 88% Pr, 87% Tb and 78% Y.
Counter –Current Leach
Leach tests were fairly steady during the pilot campaign and 85-90% (average 87%)
of total REEs was extracted. The average base metal extraction was 24% Fe, 16%
Al, 83% Mg, 79% Mn and 99% Ca. At steady state conditions, the extraction of
CREEs (total acid 529 kg/t at 45 oC) were 82% Dy, 88% Eu, 89% Nd, 89% Pr, 85%
Tb and 78% Y with 21% iron extraction.
The overall hydrochloric acid dosage was 480 kg/t , however actual consumption of
fresh hydrochloric acid was 350 kg/t due to internal acid recycling. A retention time of
2.46 hours for the pre-leach step plus 1.09 hours for the leach step was sufficient to
leach the REE for this material (COMP D) and to keep base metal extraction to a
The final leach residue composition averaged 1.10% TREE, 437 g/t Th, 77 g/t U,
5.29% Al, 16.5% Fe, 6.43% K and 19.1% Si.
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