Achieves 98% NdPr Recoveries In Its High-Grade Concentrates
Commerce Resources Corp. (TSXV:CCE) (OTCQX:CMRZF) continues to make good progress in its metallurgical programme to produce samples of mixed rare earth carbonate (REC) concentrate to satisfy several requests by global processors.
As part of this programme, continued bench-scale flowsheet development, ahead of scale-up and bulk processing, has resulted in the highest rare earth element (REE) recoveries to date into the combined high-grade monazite mineral concentrate1 as well as into the subsequent sulphation crack water-leach liquor phase (i.e., the pregnant leach solution or PLS) Highlights include:
- Monazite mineral concentrate grade of approximately 40% rare earth oxide (REO) at 82% recovery and 3.2% mass pull (recovery and mass pull with reference to unprocessed whole rock).
- Recoveries of 98% Nd, 98% Pr, 95% Tb, and 90% Dy into the PLS (with reference to the mineral concentrate1).
- Combined overall NdPr recovery of approximately 78% into the PLS (with reference to unprocessed whole rock).
The flowsheet for the Ashram REE/ Fluorspar Deposit, developed by Hazen Research, uses conventional unit processes to produce a high-grade rare earth mineral (monazite) concentrate that is comparable to active global hard-rock REE producers.
Specifically, the Ashram flowsheet utilises a flotation – HCl leach – magnetic separation process approach to achieve high-grade (>40% REO) monazite concentrates1 at high recovery comparable to active global producers.
In the current work, flotation concentrate produced from the 2015 pilot plant operation was used as feed to the subsequent HCl leach and magnetic separation stages, which were completed at bench scale and resulted in monazite concentrate grades of approximately 40% REO at 82% overall recovery. The monazite concentrate1 was then mixed (in ~50 g batches) with concentrated sulphuric acid (H2SO4) and heated to ~220°C in a stirred pot over a ~3-hour period to convert the contained REEs into soluble rare earth sulphates (i.e., the ‘sulphation crack’), which were then dissolved in a water leach to bring the REEs into solution (i.e., the PLS).
President, Chris Grove, said the recent test work resulted in the highest recoveries of REEs achieved to date in the sulphuric acid – water leach stage, at 98% for NdPr, as well as the highest overall recoveries achieved to date from unprocessed rock into the PLS, at approximately 78% NdPr.
All major hard rock REE mines globally produce mineral concentrates of at least 35-40% REO, which are then placed into solution and processed downstream into marketable products. Such high grades of mineral concentrate considerably reduce the downstream processing cost and risk through lower reagent use, fewer deleterious elements entering solution, and a smaller hydromet plant requirement by comparison.
With respect to the Ashram Deposit, test work has now demonstrated that >80% of the REEs in the unprocessed deposit material can be effectively concentrated (i.e., recovered) into just 3-4% of the original mass, resulting in a significant upgrade factor of over 21 times the original head grade.
In addition, the recent work has now demonstrated that 98% of the NdPr contained in this concentrate can be put into solution for downstream recovery. These results are also a strong improvement on the 90-95% REE recoveries into solution achieved in prior test programmes.
“The ongoing work on the Ashram flowsheet has demonstrated that very high-grade monazite concentrates at high recoveries have been produced, and there is still room for improvement,” Mr Grove said.
“Moreover, the prior bench-scale work has demonstrated that producing high-grade monazite concentrates1 at high REE recoveries is repeatable, and now, the current test program has demonstrated that high REE recoveries into solution at the sulphuric acid water-leach stage, are also repeatable.
“Our metallurgical results to date continue to solidify our belief in Ashram as a potential low-cost leader for mixed REC / NdPr supply to the global market.”
In the next steps of the process flowsheet the leach liquor produced from the sulphuric acid water-leach stage will be treated by solvent extraction (SX) to reject thorium followed by SX to purify and concentrate the REEs. A mixed REC, high in NdPr, will then be precipitated from the SX strip liquor. This test work is currently being completed on the bench scale and in parallel to the scale-up of the sulphuric acid pot digestion stage from 50 g batches to 2.5 kg batches. The test work will continue to scale up until approximately 2.5 kg of on-spec mixed REC is produced.
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