NI43-101Pre-Feasibility Study Report - page 216

Rare Element Resources
Bear Lodge Project
Canadian NI 43-101 Technical Report
October 9
, 2014
10135-200-46 - Rev. 0
Overall Recovery
The overall recoveries of CREEs from Comp B, that were ultimately transferred into
the oxalate precipitate cake were: 87% Dy, 93% Eu, 95% Nd, 95% Pr, 89% Tb and
81% Y. In this PFS, overall recovery calculations combine REE extraction and
precipitation efficiencies. Also, overall circuit recovery did not include rare earths that
should be captured downstream as oxalate crystals and recycled back to the process.
Counter –Current Leach
The specific REE recoveries in the counter current leach stream ranged from 85% to
99% (averaging 93%). But, acid digestion of base metals was comparatively low at
the same temperature (45
C). Leach efficiencies of Iron, Mn, Al, Ba, Mg and Ba are
listed below.
Iron :
96% to mid-20%.
27% to 7%
28% to 7%,
Magnesium 97% to 73%
Manganese 99% to 65%
At steady state leach conditions (297 kg/t, acid, at 45°C), the recoveries of CREEs
were as follows: 89% Dy, 88% Eu, 96% Nd, 97% Pr, 92% Tb and 86% Y. The
corresponding extraction of iron was 44% using a full HCl recycle system, acid
consumption averaged 393 kg/t (100% HCl per ton of ore) for Comp B. Residence
time in the pre-leach and leach units were 1.4 and 1.95 hr, respectively.
The final leach residue cake assayed: 0.27% TREE, 96 g/t Th, 38 g/t U, 7.68% Al,
6.09% Fe, 9.44% K and 26.0% Si indicating selective digestion of REEs over base
metals and silicates.
Precipitation Cascade
In the oxalate precipitation circuit, the specific recoveries of CREEs at steady state
conditions were: 98% Dy, 99% Eu, 96% Nd, 95% Pr, 98% Tb and 91% Y. Thorium
was co-precipitated with rare earths (99.8%) but uranium and base metals were
rejected. In terms of product purity, rare earth oxalate cakes contained +97%TREE
(44.6%TREE) with impurities averaging 1.24 wt.% calcium, 0.9 wt.% silica and 0.497
1...,206,207,208,209,210,211,212,213,214,215 217,218,219,220,221,222,223,224,225,226,...587
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