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Rare Element Makes Progress Toward a Commercial Process with Rare-Earths Metallurgical Testing

^{Published on 2010-08-18 06:10:30 - Market Wire}
 

 1. With scrubbing/attritioning in water, a preconcentrate is produced with a recovery of approximately 90% and a grade up to 20% rare-earth oxide (REO); the REO resides in the finer fractions (-100 to- 500 mesh). 2. Hydrochloric acid leaching of the preconcentrates in an agitation leach system gives a recovery of about 80 to 85% of the total REO from the original mineralized material in the same general proportions as the original REO distribution. 3. Additional testing is being conducted to optimize the processing methods. 

 Table 1. Mineralogy of Large Sample Collected from Surface in Fall 2009 ---------------------------------------------------- Mineral Phase Abundance ---------------------------------------------------- Biotite 26 ---------------------------------------------------- K feldspar 21 ---------------------------------------------------- Fe-Mn oxides 16 ---------------------------------------------------- Barite 2 ---------------------------------------------------- Apatite 1 ---------------------------------------------------- Ilmenite and rutile 1 ---------------------------------------------------- Other minor silicates and oxides 7 ---------------------------------------------------- Bastnasite-group minerals 20 ---------------------------------------------------- Monazite 2 ---------------------------------------------------- Mn+Fe(REE) 3 ---------------------------------------------------- REE-nano 2 ---------------------------------------------------- 

 ------------------------------------------------------------------------- Parameter REO Oxide Distribution % ------------------------------------------------------------------------- Cutoff (%REO) 1.5 Million Tons Resource 8.0 Tonnage Factor (ft(3)/ton) 13.7 %REO 3.62 Million lbs REO 582 ------------------------------------------------------------------------- %Cerium Oxide Ce(2)O(3) 1.66 45.9 %Lanthanum Oxide La(2)O(3) 1.06 29.3 %Neodymium Oxide Nd(2)O(3) 0.52 14.4 %Praseodymium Oxide Pr(2)O(3) 0.16 4.4 %Samarium Oxide Sm(2)O(3) 0.088 2.4 %Gadolinium Oxide Gd(2)O(3) 0.045 1.2 %Yttrium Y(2)O(3) 0.032 0.9 %Europium Oxide Eu(2)O(3) 0.021 0.6 %Dysprosium Oxide Dy(2)O(3) 0.018 0.5 %Terbium Oxide Tb(2)O(3) 0.0075 0.2 %Erbium Oxide Er(2)O(3) 0.0020 0.1 %Ytterbium Oxide Yb(2)O(3) 0.0012 (less than) 0.1 %Lutetium Oxide Lu(2)O(3) 0.00016 (less than) 0.1 %Holmium Oxide Ho(2)O(3) 0.00100 (less than) 0.1 %Thulium Oxide Tm(2)O(3) 0.00015 (less than) 0.1 ------------------------------------------------------------------------- 

 ------------------------------------------------------------------------- % REO % REO Grams % Weight Assay Distribution ------------------------------------------------------------------------- +1/4" 9100 46.96 1.12 6.52 ------------------------------------------------------------------------- -1/4" 10280 53.04 14.22 93.48 ------------------------------------------------------------------------- Total Ore 19380 100 8.07 100 ------------------------------------------------------------------------- 

 ------------------------------------------------------------------------- REO Product W t. (%) REO (%) Distribution ------------------------------------------------------------------------- -500 Mesh 28.60 21.68 79.10 -325 Mesh 32.30 20.60 84.80 -200 Mesh 35.60 19.49 88.60 -100 Mesh 38.10 18.54 90.20 -48 Mesh 40.10 17.83 91.10 ------------------------------------------------------------------------- 

 Figure 1. Conceptual Flowsheet of Preconcentration Process: [ http://files.newswire.ca/675/Rare_Element_Fig1.pdf ] Figure 2. Conceptual Flowsheet of Leaching and Concentration Process: [ http://files.newswire.ca/675/Rare_Element_Fig2.pdf ]

 - The initial wet screening and light scrubbing at +3-inch size would provide a throw away product amounting to about 10 wt.% of the original sample, and containing about 1.0% of the total REO value. - After proper scrubbing and screening at 1/4-inch, it appears technically feasible to discard an additional 35 wt % of oversize material with a loss of less than 1.0% of the total REO content. - Simple wet scrubbing in autogenous or tube milling or log washing of the ROM mineralization, followed by screening at 1/4-inch, allows discard of more than 45 wt % oversize material with a loss of less than 6% of the total REO content. Accordingly, initial scrubbing and screening is an integral and important step in the development of the overall flowsheet for treating the oxide mineralization. - Additional attritioning of the minus 1/4-inch product assaying 14.2% REO in a Lightning Attrition Scrubber allows further upgrading of the preconcentrate as shown in Table 3. - It appears technically feasible to obtain an 18 to 20% REO product (preconcentrate) in about 40 wt % of the original sample, with a total REO recovery of about 90%. This light attritioning step would be an important and integral step in the overall flowsheet for treating the oxide mineralization. The selection of the best size for upgrading (preconcentrates) should be based on a cost-benefit analysis after projecting the capital and operating costs of the proposed flowsheet (including scrubbing, attritioning and leaching steps). - Although both H(2)SO4 and HCl leaching agents are applicable for dissolving REO from preconcentrates, HCl is found to be a more effective reagent. More than 90% of the contained REO values from the preconcentrate are recovered using HCl as the leaching agent. However, cost and environmental considerations dictate that HCl be regenerated and recycled in this hydrometallurgical process. - The dissolved REO values from the pregnant leach solution can be precipitated as an REO-oxalate compound, which is similar to a rare- earth carbonate concentrate. Preliminary tests indicate that all rare earths are recovered in the same general proportions as their original distributions (Table 2). - The HCl remaining in the spent leach solution can be recovered upon the addition of H(2)SO(4), which drives off HCl acid vapor to obtain HCl concentration of 20.2% for recycle.