Cobra Resources (LSE:COBR) has reduced ammonium sulphate concentration by 40% in laboratory tests at its Wudinna Rare Earths Project in South Australia. The lower-strength solution retained about 90% of the key rare earth recoveries achieved with a stronger solution.
The Australian Nuclear Science and Technology Organisation (ANSTO) completed the 24-hour desorption tests on bulk composites from the Boland and Head prospects.
At Boland, a 0.3 molar (M) solution at pH 3 recovered 70% of neodymium-praseodymium (NdPr), 67% of dysprosium-terbium (DyTb), and 67% of heavy rare earth elements (HREE). Those results retained 91–93% of the recoveries achieved at the industry-standard concentration of 0.5M.
Head showed a similar response. Testing at 0.3M recovered 36% NdPr, 52% DyTb, and 53% HREE — retaining 90–91% of the recoveries recorded with the stronger solution.
Even without added ammonium sulphate, acidified site groundwater recovered 51% NdPr, 46% DyTb, and 50% HREE at Boland. Uranium recovery into solution fell from 29% at 0.5M to 5% without the reagent.
Managing Director Rupert Verco says the next step is to weigh the lower reagent requirements against the change in recovery.
“At Boland, magnet rare earth recoveries were only reduced by 9% with a 40% reduction in ammonium sulphate reagent when compared to the industry standard 0.5M, while acidified site groundwater with no added ammonium sulphate recovered around half of the key magnet and heavy rare earths,” Verco says.
“This operating flexibility matters because recovery cannot be assessed in isolation. Lower reagent concentrations may reduce cost, supply exposure, and the salinity load introduced to the aquifer.”
Scoping Study weighs reagent trade-offs
The composites represent 26 mineralised intervals from 24 drill holes. All tests used saline groundwater sourced from the project.
Cobra cautions that the lower-reagent conditions are not commercial operating parameters. Its ongoing Scoping Study will assess recovery, reagent consumption, solution chemistry, and economics, with further column testing and solution management studies planned.
The findings follow ANSTO purification test work that retained more than 90% of magnet and heavy rare earths while indicating reduced radionuclide concentrations, as previously reported by Mining.com.au.
Cobra expects to announce Wudinna’s maiden mineral resource estimate shortly, followed by further Scoping Study updates.
Cobra Resources is a UK-listed critical minerals explorer advancing the Wudinna Rare Earths and Manna Hill Copper projects in South Australia.
Write to France Pinzon at Mining.com.au
Main image: Cobra Resources
