Ion Exchange and Nanofiltration Redefine Rare Earth Processing Flowsheet - First Mover Advantage for OD6 Limited? Is It Time for Investors?
- Noel Ong
- Aug 13
- 8 min read
Announcement
OD6 Metals Limited (ASX: OD6) has announced a significant step forward in rare earth processing at its flagship Splinter Rock Rare Earth Element (REE) Project in Western Australia (Figure 1). The integration of Ion Exchange (IX) and Nanofiltration (NF) technologies into the heap leach flowsheet is yielding transformational results—enhancing impurity removal, reducing acid consumption, and increasing recovery efficiency.
This innovation not only slashes processing costs but also consolidates Splinter Rock's position as Australia's leading clay-hosted rare earths project.
Figure 1: Splinter Rock Project location (source: OD6)
Managing Director Brett Hazelden commented:
“Our flowsheet development has been led by a clear vision—delivering a high-quality product that meets the needs of global customers. We’ve focused not only on product purity and recovery but also on reducing capital and operating costs to ensure robust project economics.”
“Integrating Ion Exchange into our flowsheet allows us to de-risk and improve the impurity removal process, specifically targeting aluminium, iron, uranium and thorium—key drivers of product payability.”
“The combined heap leaching and impurity removal process flowsheets that we have tested in conjunction with ANSTO are currently being assessed by CPC Engineering to determine the optimal development pathway.”
“It is also pleasing to see the Hon Madeleine King MP discussing Rare Earths at the Diggers and Dealers Mining Forum this week. The innovations of heap leach, nanofiltration and ion exchange strongly position the Splinter Rock Rare Earth Project for potential government support moving forward.”
Key Highlights - Rare Earth Processing Creating Value for OD6 Metals Limited.
Ion Exchange (IX) Enhances Product Purity
IX technology effectively removes iron (Fe), aluminium (Al), uranium (U), and thorium (Th), resulting in a cleaner rare earth product.
Nd and Pr recoveries post-impurity removal remain strong at ~75%.
Losses of REEs during the IX process are minimal (<1%).
Uranium and Thorium Removal Improves Payability
ANSTO testing confirms U and Th levels in final product are <0.001 wt%, broadening appeal to global offtake markets and enhancing pricing potential.
Acid Reduction through Nanofiltration
84.5% hydrochloric acid (HCl) recovery enables major reduction in reagent use.
Acid consumption cut from 37.2 kg/t to ~7.5 kg/t, improving environmental and cost profiles.
94% of REEs retained in the retentate; only 6% in the recycled acid stream.
Efficient Heap Leach Recoveries at Inside Centre
79% recovery for Magnetic Rare Earth Elements (MagREE).
~80% for Nd and Pr; 60–70% for Dy and Tb.
Recovery trends improve with longer leach durations (80+ days).
Optimised Processing and Flowsheet Design
Simplified heap leach–nanofiltration–ion exchange–impurity removal circuit.
Eliminates high-cost infrastructure like leach tanks and thickeners.
Downstream circuit size reduced by 69%, leading to smaller plant footprint and lower CAPEX.
Ongoing Engineering Evaluation
CPC Engineering is conducting an Optioneering Study to determine the optimal development pathway for Splinter Rock, considering cost, recovery, scalability, and product quality.
Processing Innovation at Splinter Rock
The incorporation of IX and NF technologies is part of a broader flowsheet evolution aimed at cost-effective and scalable processing. The updated flowsheet (Figure 2) includes:
Figure 2: Indicative processing steps including Heap Leach, Nanofiltration, plus Ion Exchange & Impurity Removal (source: OD6).
Heap Leach is the foundation—an energy-efficient, scalable approach well suited to the Splinter Rock deposit’s mineralogy.
Nanofiltration follows, recovering over 80% of hydrochloric acid, concentrating REEs in the retentate, and significantly reducing downstream processing volume.
Ion Exchange plays a key role in selectively removing impurities like Fe, Al, U, and Th while preserving valuable rare earth elements.
Impurity Removal is then carried out through a two-stage, pH-controlled precipitation process that improves both product purity and overall REE recovery (Figure 3).
The Chemistry:
Ion Exchange reduces REE loss and improves IR efficiency.
NaOH preferred for pH control: Stage 1 (~3.5), Stage 2 (~4.1–4.4).
Final product precipitated at pH 7.1–7.5.
~5% Nd/Pr loss; ~75% overall REE recovery.
Dy/Tb optimised at lower pH in future work.
Figure 3: Impurity Removal Curve showing decreasing Al and Fe concentration as pH is increased (source: OD6)
Finally, Mixed Rare Earth Carbonate (MREC) Precipitation trials are underway to produce a saleable rare earth carbonate or hydroxide product, with results expected to further optimise the final flowsheet.
Inside Centre Prospect: Flagship Performance.
The Inside Centre area is the current focus of development and metallurgical testing:
Indicated Resource: 119Mt @ 1,632ppm TREO.
Heap Leach Recoveries:
79% for MagREEs
~80% for Nd & Pr
60–70% for Dy & Tb
Long Leach Duration Effect: Ongoing recoveries observed after 80+ days.
Low Strip Ratio: Adds to the project’s low-cost profile.
Less than 10% of the project area explored, providing significant growth runway.
Next Steps
OD6 has completed a suite of metallurgical testwork, with final results for the Mixed Rare Earth Product, either as Mixed Rare Earth Carbonate (MREC) or Mixed Rare Earth Hydroxide (MREH) —expected shortly. These outcomes will help confirm product quality and recovery efficiency across the full flowsheet.
In parallel, CPC Engineering is progressing an Optioneering Study aimed at selecting the optimal development pathway. This study will weigh cost, recovery, scalability, and product specifications to guide final flowsheet design. Completion is expected within the current quarter.
To validate the process at a larger scale, OD6 plans to undertake pilot-scale testing using approximately one tonne of diamond core material. This work will produce kilo-scale quantities of MREC product to support offtake discussions and further optimisation.
Further downstream, the company is also assessing options for converting the mixed rare earth carbonate or hydroxide into individual rare earth oxides. This step is critical for aligning final products with market demand and broadening potential customer reach.
Technology in Focus: What is Ion Exchange (IX)?
IX is a chemical process where ions are exchanged between a liquid and a resin (Figure 4). In the Splinter Rock process:
IX removes impurities, eg Fe, Al, U, and Th with high selectivity.
Operates at low temperatures and requires minimal energy.
<1% of REEs lost in the IX process.
This step enables a smaller, more efficient downstream circuit and helps meet strict export requirements.
Figure 4: Example of an Ion Exchange system (source: OD6)
Technology in Focus: What is Nanofiltration (NF)?
NF uses pressure-driven membranes to separate substances by size and charge (Figure 5). In REE processing:
It recovers over 80% of HCl.
Concentrates REEs in the retentate for further processing.
Reduces downstream circuit volume by ~69%.
Operates efficiently in remote, modular setups.
Figure 5: Example of a Nanofiltration system and the membrane utilised (source: OD6)
Samso Concluding Comments
The clay-hosted REE story is one that I have been re-following with interest lately. For those who have been following Samso since the first Coffee with Samso with Brett Hazelden, you would know that we have been big fans of the developments of the sector. In our first episode together, I asked Brett to tell us how this clay-hosted REE business works. You can watch that conversation below.
OD6 Metals Limited (ASX: OD6) - The Rare Earth Elements Story:
The sector has had a terrible two years with REE prices experiencing a steep decline. I have been watching this space closely to see how the outcome of the big US push to have a second train for the REE downstream process. I have been wanting to get content made to follow this process, and companies that have been in this space have been shy to speak out. In fact, several have moved on from this story and are now focusing on other commodities.
OD6 Metals may be the last man standing in Australia, and it looks like it continues to lead from the front in redefining the economics of clay-hosted rare earth projects in Australia. The recent news, and I do not claim to understand, may start conversations again. The recent ASX release showing that nanofiltration and ion exchange are now proving their value in both cost reduction and processing efficiency, OD6's Splinter Rock is evolving beyond a resource story—it’s becoming a demonstration of smart engineering and disciplined innovation.
Does this mean that while many rare earth developers are still working through the basics, OD6 is advancing into value engineering? According to OD6, the acid recovery rates, high REE retention, and processing simplification are not just theoretical—they’re backed by rigorous ANSTO testing and flowsheet modelling. These are the practical steps that derisk development and add weight to long-term value propositions.
What’s especially encouraging is that all of this is being achieved on just a fraction of the tenement footprint. With less than 10% explored and a Tier-1 resource already defined, the growth runway is compelling. The addition of nanofiltration and IX simply improves the project’s scalability and economic integrity.
Figure 6: OD6 share price chart as of 7th August 2025. A market capitalisation of AUD $4.65M is making any new input to the business of OD6 very attractive to investors. (source: commsec).
The market capitalisation of under AUD $5M will make any value adding to the OD6 very attractive for serious DYOR (Figure 6). As the "Western" narrative of creating a new train of downstream REE processing business work, the refinement of the OD6 REE story will definitely create a First-Mover advantage for the likes of OD6 Metals Limited. Figure 6 shows that there is still a lot of value that can be recovered from its share price highs of 2022.
For those tracking Australia’s role in the global rare earths supply chain, Splinter Rock represents more than just a deposit—it’s a test case in how technology and geological advantage can combine to produce low-cost, high-margin production in a geopolitically strategic sector. OD6 is quietly building something significant. The market may not be pricing that in—yet.
The Samso Way – Seek the Research
In clay-hosted rare earths, success hinges on innovation. OD6’s partnership with ANSTO, emphasis on practical flowsheet engineering, and disciplined testwork progression is a textbook example of how to derisk development. As investors, look to where margins are created, not just in the ground, but in how it's processed. At Splinter Rock, the value is engineered in.
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