Craig Taylor reports
DEFENSE METALS HYDROMETALLURGY TEST PROGRAM ACHIEVES ~90% RARE EARTH ELEMENT EXTRACTION FROM WICHEEDA FLOTATION CONCENTRATE
Defense Metals Corp. has received final bench-scale hydrometallurgical test program results for the Wicheeda rare earth element property from SGS Canada Inc. Samples of Wicheeda flotation concentrate, used in a hydrometallurgical test program, led to the successful development of a flowsheet capable of processing the concentrate to a high-grade mixed REE hydroxide precipitate. Highlights of the recently completed hydrometallurgical test program include:
Initial processing through mild hydrochloric acid leach to extract gangue minerals while leaving REE (rare earth elements) in the leach residue;
- High REE extraction from flotation concentrate of approximately 90 per cent into a chloride-based leach solution with opportunities identified to increase recoveries even further;
Simple treatment of the leach solution with limestone achieved high (94 to 100 per cent) removal of impurities, such as iron, phosphorous and thorium with only minor (2 to 4 per cent) REE losses;
Simple treatment of purified liquor with hydrated lime led to the production of a high-grade 67.5-per-cent TREE (total REE) mixed-REE hydroxide precipitate at high (99 to 100 per cent) critical REE recovery from solution;
Overall recoveries of 70 to 75 per cent TREE from bulk sample to a high-grade mixed REE hydroxide precipitate and up to 76 to 78 per cent TREE with reprocessing of the final leach residue;
Regeneration of 20 per cent (w/w) hydrochloric acid from final process liquors for reuse in the leaching operation.
As noted herein, flowsheet improvement options have been identified that will be investigated through further testing, including: locked-cycle testing to investigate effect of recycling regenerated hydrochloric acid and sodium hydroxide; optimization of the gangue leach circuit to limit REE losses; reprocessing of leach residue back to the caustic crack stage to improve overall REE extraction; adoption of two-stage impurity removal process to limit the overall extent of REE co-precipitation; and inclusion of hydrochloric acid and caustic regeneration to reduce overall reagent consumption.
Once optimized, continuous hydrometallurgical pilot plant testing is required to confirm overall circuit operability, to confirm product recoveries, product grades and reagent consumptions under continuous conditions, and to produce bulk quantities of purified mixed REE product for further separation testing.
Details of the process development testwork carried out at SGS will be included in a joint Defense Metals/SGS paper, which will be presented at the Processing of Critical Materials Symposium (part of the Conference Of Metallurgists) in August, 2020, in Toronto.
Craig Taylor, chief executive officer of Defense Metals, stated: "These hydrometallurgical test results, which showed REE extractions of approximately 90 per cent from flotation concentrate, in conjunction with our recently released locked-cycle flotation tests that produced a high-grade 48.7-per-cent-TREO concentrate, conclude a very successful year-long metallurgical flowsheet optimization process. Defense Metals believes these are exceptional results that show the Wicheeda REE deposit mineralization is readily amenable to processing via well-established flotation and hydrochloric acid leach/caustic crack REE extraction methods. Based on these positive results, we expect to finalize our plans to commence continuous pilot plant testing in the near future."
The overall hydrometallurgical flowsheet is chloride based and uses hydrochloric acid to dissolve gangue minerals away from the REE-carrying minerals. The REE-containing leach residue is subsequently processed in a caustic treatment step to convert REE phosphates and fluorides into acid soluble REE hydroxides. The REE hydroxides are leached in hydrochloric acid, and the leach solution is treated to remove impurities, such as iron, aluminum, phosphorous and thorium. A purified and mixed REE product suitable for further REE separation can be produced either by hydroxide or oxalate precipitation. Final filtrates from gangue leaching and REE precipitation are combined and reacted with sulphuric acid to produce 20 per cent (w/w) hydrochloric acid for reuse.
About the Wicheeda REE property
The 1,708-hectare Wicheeda REE property, located approximately 80 kilometres northeast of the city of Prince George, B.C., is readily accessible by all-weather gravel roads and is nearby to infrastructure, including power transmission lines, the CN railway and major highways.
Geologically, the property is situated in the Foreland belt and within the Rocky Mountain trench, a major continental geologic feature. The Foreland belt contains part of a large alkaline igneous province, stretching from the Canadian Cordillera to the southwestern United States, which includes several carbonatite and alkaline intrusive complexes hosting the Aley (niobium), Rock Canyon (REE) and Wicheeda (REE) deposits.
The Wicheeda REE property is underlain by Kechika group metasedimentary rocks that are intruded by the southeast-trending Wicheeda carbonatite and a deformed plug or sill approximately 250 metres in diameter that hosts significant REE mineralization. This intrusion comprises a ferroan dolomite carbonatite core, which passes gradationally outward into calcite carbonatite. The REE mineralization is primarily hosted by the dolomitic carbonatite.
The scientific and technical information contained in this news release as it relates to the Wicheeda REE property has been reviewed and approved by Kristopher J. Raffle, PGeo (British Columbia), principal and consultant of Apex Geoscience Ltd. of Edmonton, Alta., a director of Defense Metals, and a qualified person as defined in National Instrument 43-101 (Standards of Disclosure for Mineral Projects). Mr. Raffle verified the data disclosed, which include a review of the analytical and test data underlying the information and opinions contained therein.
Methodology and quality assurance/quality control
Head grade, batch and locked-cycle flotation, and hydrometallurgical product assays for cerium, lanthanum, neodymium and praseodymium oxides were determined through lithium-borate fusion of a 0.5-gram sample analyzed through wavelength dispersion X-ray fluorescence (WD-XRF). The remaining rare earth elements for the head sample were determined through 0.5-gram sodium peroxide fusion multielement ICP-MS.
The SGS analyses included a quality assurance/quality control program, including the insertion of rare earth element standard and blank samples. Defense Metals detected no significant QA/QC issues during the review of the data. Defense Metals is not aware of any drilling, sampling, recovery or other factors that could materially affect the accuracy or reliability of the data referred to herein. SGS is an ISO/IEC 17025 and ISO9001:2015 accredited laboratory. SGS is independent of Defense Metals.
About Defense Metals Corp.
Defense Metals is an advanced mineral exploration company focused on the acquisition of mineral deposits containing metals and elements commonly used in the electric power market, military, national security and the production of green energy technologies, such as: high-strength alloys and rare earth magnets. Defense Metals has an option to acquire 100 per cent of the 1,708-hectare Wicheeda rare earth element property, located near Prince George, B.C., Canada.
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