- Samples were selected for metallurgical test work across four large prospects at OD6’s Splinter Rock rare earths project in WA
- Head samples were assayed prior to, and then post, screening out of material with greater than 75um particle size
- The opportunity exists for screening size to be further optimised to maximise rare earth recovery while reducing acid consumption
Special report: Metallurgical test work conducted at OD6’s flagship Splinter Rock project has demonstrated a significant increase in total rare earth oxide (TREO) grades.
OD6 Metals (ASX:OD6) has been working on simplifying its rare earths processing flow sheet, based on metallurgical test work completed to date with the Australian Nuclear Science and Technology Organisation and CSIRO.
The company has partnered with the two research organisations to improve exploration and extraction of rare earth clay deposits at the Splinter Rock project in WA’s Esperance-Goldfields region.
Funds from a recent $1.5m placement were spent on the ANSTO program, focusing on optimising the leach recovery and impurity removal of coarse material across various regolith types at four large prospects (Prop, Centre, Scrum and Flanker).
OD6’s goal is to produce a mixed rare earth carbonate product that will enable the completion of the scoping study.
Metallurgical results from 13 samples
A total of 13 Phase 1 samples were selected from a wide variety of clays, locations and depths to develop a geo-metallurgical understanding of acid consumption and recovery.
Head samples were assayed prior to, and then post, screening out of material with greater than 75um particle size.
The screened and unscreened samples were subjected to the standard ANSTO diagnostic leach tests at 25 g/L hydrochloric, at ambient conditions and pressures, over a 6-hour period to determine if screening resulted in decreased acid consumption and to identify any impacts on MagREO recovery.
Metallurgical testing of screened material at 75um delivered up to 79% reduction in hydrochloric acid (HCl) consumption (35% average reduction) to ~10kg HCl/t total screened ore.
It also improved TREO grades by up to 224%.
OD6 says the opportunity exists for screening size to be further optimised to maximise rare earth recovery while reducing acid consumption.
Benefits to overall cost profile of operations
“Leaching of the finer faction material has the corresponding benefit of consuming an average of 35% less acid as a total of product processed,” OD6 managing director Brett Hazelden says.
“This provides a potential benefit to the overall cost profile of any future operation by reducing the amount of material that needs to be leached with acid by approximately 40%.
“Additional screening size optimisation will occur in future phases of work providing the potential for further improvements.”
The Chlor-Alkali process
OD6 has obtained information from chlor-alkali electrolyser vendors and experts to determine if owning and operating a site-based facility is a viable processing option.
The chlor-alkali process involves passing an electric current through high-purity sodium chloride (NaCl or salt) brine to produce hydrogen, chlorine and caustic soda; the hydrogen and chlorine can then be combined into hydrochloric acid.
A single chlor-alkali electrolyser is indicatively capable of treating more than 5Mtpa of REE bearing clay.
Given power being the main cost driver, OD6 envisages that low-cost power supply would be sourced from an owned and operated hybrid power system consisting of solar, wind turbines, energy storage and gas or diesel-powered generators.
It is understood that a similar facility currently powering the Esperance township and surrounding areas is achieving a 70% renewable power penetration rate which is a significant achievement that OD6 should aim to replicate.
This article was developed in collaboration with OD6 Metals, a Stockhead advertiser at the time of publishing.
This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.