Plateau Uranium Inc. ("Plateau Uranium" or the "Company") is pleased to announce new metallurgical test work results from its Macusani Plateau uranium project in Peru. The work was completed by TECMMINE, a Peruvian metallurgical consulting company based in Lima, Peru, and was reviewed by Grenvil Dunn of Hydromet (Pty) Ltd. ("Hydromet"). The test work forms part of the Company's efforts to unlock value from the significant lithium resources contained within its uranium deposits.
The Company is continuing additional test work on uranium, lithium and other associated metals with the intention of further optimizing the process and establishing potential capital and operating costs for producing uranium and lithium from the Macusani deposits.
- The new leach test work commenced in August 2016 with samples typical of Macusani uranium mineralization from all uranium deposits considered in the Company's PEA (U-Li-rich) as well as Li-rich/U-poor samples.
- Regardless of initial uranium concentration, consistent lithium recoveries of 61 to 73% were achieved into leach solutions at temperatures between 65 to 85°C using various concentrations of sulphuric acid.
- Uranium recoveries of 98-99% were achieved for Macusani uranium mineralization along with the excellent lithium recoveries of up to 73%.
- The extensive test work has streamlined the Company's understanding of the process, resulting in a simple, straightforward crush-grind with a warm sulfuric acid leaching process.
- Additional work is planned in Peru and will be followed up with further leaching and precipitation work at international processing experts, SGS Laboratories, in Australia. A representative 300 kg bulk sample of Macusani uranium-mineralization has been shipped and is already in Australia at SGS.
- The outcome of this work will establish potential capital and operating costs to produce lithium as a by-product, and will subsequently determine its potential positive impact to the Macusani project.
Ted O'Connor, CEO of Plateau Uranium commented: "These results are extremely positive with excellent uranium and lithium recoveries from the Macusani mineralization. The low temperature and simple reaction process employed indicates that atmospheric leaching is appropriate, reducing potentially excessive Capital and Operating costs associated with pressure leaching. This represents an excellent opportunity to add value to our already strong uranium project economics. The next phase of test work will be focused on establishing more detail on the CAPEX and OPEX numbers to quantify the potential value-added impact of uranium and lithium co-production."
The new leach test work commenced in August 2016 using lithium-rich samples with background uranium and uranium-lithium-rich samples from the Macusani deposit mineralization. The lithium content ranges from 640 to 806 ppm Li in all samples. The uranium content ranges from background levels (7ppm U) in the U-poor samples to 568-629 ppm U in the mineralized samples from the various uranium deposits.
Several parameters were varied during the leach tests, including: crushing grind size; acid concentration; leach time and temperature. Leaching was undertaken at atmospheric pressure in stirred tank reactors employing sulfuric acid as the lixiviant. Additionally, initial scoping test work employed roasting, calcining and acid-curing.
The tests covered temperatures ranging from 50°C to 550°C. Although very high temperatures above 180°C usually guarantee high Lithium recoveries of up to 87% in earlier test work, the objective of this most recent work was to reach potentially economic lithium recoveries at leaching temperatures below the water boiling point. The initial scoping test work employing more aggressive conditions did not confirm any significant benefit over the more moderate temperature and atmospheric pressure tank leach processes. In all, over 150 separate leach test runs have been completed in Peru over the past several months. The conclusions of this phase of test work have resulted in a very simple, straightforward flow sheet without the aggressive processing conditions normally associated with the recovery of lithium from ores.
Consistent lithium recoveries of 61 to 73% were reported from all samples employing a sulfuric acid leach at a variety of acid concentrations and at temperatures of 65 to 85°C. Samples from the Macusani uranium deposits displayed consistent uranium recoveries of 98-99% across all temperatures.
Sulfuric acid consumption in the leach varied from 50-140 kg acid/tonne of material processed and was sufficient to simultaneously extract both uranium and lithium. Higher acid consumptions were related to finer grind sizes, and coarser grind sizes had much lower acid consumptions with identical lithium and uranium recoveries, thus giving upside to the potential project economics. The current, and planned test program is examining the grind versus recovery trade off with encouraging results.
Apart from lithium and uranium other elements were also leached during the tests, mainly potassium, rubidium and cesium. These will also be evaluated further in the additional leaching-precipitation work planned.
Mr. Grenvill Dunn, Pr Eng (RSA), C Eng (UK), FIChE, MSAIMM, MSAIChE of Hydromet Pty Ltd, a consultant to the Company, is a Qualified Person as defined under National Instrument 43-101 Standards of Disclosure for Mineral Projects, and has reviewed and approved the scientific and technical information contained in this release.