Looks like their sweet spot is pH 1.5-2.0. Read from 19...

Looks like their sweet spot is pH 1.5-2.0. Read from 19 September 2022 announcement.

Metallurgical test results indicate viable processing pathway for Koppamurra Rare Earths ProjectLeach optimisation test work has resulted in excellent recoveries of the four key magnet rare earth elements (REE) while reducing acid consumption and impurity dissolutionproviding potential for both an environmentally sound and commercially attractive process pathway to economically produce a high-quality specification product.

Two samples, taken from the Koppamurra prospect, were assessed for rare earth recovery characteristics

at varying pH and leach durations; KM0234_3 (1,241 ppm TREO) and KM0241_4 (2,125 ppm TREO).

Leaching in the pH range 1.5 to 2.0 showed recoveries of the four valuable magnet REEs (Nd, Pr, Tb & Dy)

were maintained, with average recoveries of 65% and up to 77%, while acid consumption from the

dissolution of iron and aluminium dropped significantly.

Acid consumption is a key economic driver in the leach process, and the reduction in consumption at

higher pH has the potential to decrease costs at a commercial scale. Reduction in iron and aluminium

dissolution reduces the risk of these deleterious components reporting to the final product on a

commercial scale. Leach test work at increased solids density on a representative composite is underway

to confirm the REE extraction response and acid consumption