Heap Leaching: OD6 Metals’ Innovative Approach to Rare Earth Extraction

The global demand for rare earth elements (REEs) is skyrocketing, driven by the proliferation of electric vehicles (EVs), renewable energy technologies, and advanced electronics. According to a recent report, the global REE market is projected to reach $28.4 billion by 2032, expanding at a CAGR of 10.1% from 2025. This surge in demand has intensified the search for efficient and environmentally responsible extraction methods. OD6 Metals, an Australian company, is emerging as a key player in this space, pioneering an innovative heap leaching approach to REE extraction at its Splinter Rock Project in Western Australia.

Understanding Heap Leaching

Heap leaching is an industrial mining process used to extract valuable metals from ore. Instead of traditional mining methods that involve energy-intensive processes like roasting, flotation, and complex chemical treatments, heap leaching simplifies the extraction process through direct chemical dissolution. The process involves piling crushed ore into large heaps on an impermeable base and then spraying a leaching solution over the heap. As the solution percolates through the ore, it dissolves the target metals, which are then collected for further processing.

The basic steps in heap leaching are:
1. Crushing the ore: The ore containing valuable metals is crushed.
2. Spreading the ore: The crushed ore is spread over geomembrane-lined pads that are solid and water-resistant to prevent the leaching solvent from contaminating the soil.
3. Spraying leaching solvent: A leaching solvent, such as sulfuric acid, is sprayed over the pads.
4. Collecting the solution: The valuable minerals dissolved into the solution are collected.
5. Metal recovery: The valuable metals are then collected using absorption methods.

OD6 Metals’ Heap Leaching Innovation

OD6 Metals is applying a refined heap leaching process at its Splinter Rock Project, located approximately 150km northeast of Esperance, Western Australia. The company’s approach focuses on rare earth-bearing clays and incorporates several innovative steps to enhance efficiency and minimize environmental impact.

Key elements of OD6 Metals’ heap leaching process include:

Low-Acid Usage: OD6 Metals utilizes a simple, low-acid usage leaching process for rare earth-bearing clays.
Nanofiltration: This process recycles acid, concentrates REEs, and reduces liquid volume. According to a recent announcement, nanofiltration technology has enabled OD6 to recover 84.5% of hydrochloric acid for recycling while retaining 94% of REEs for further processing.
Ion Exchange (IX): Ion exchange concentrates rare earth elements and enhances the removal of iron and aluminum. OD6 Metals’ proprietary ion exchange technology has demonstrated over 90% efficiency in lab trials.
Impurity Removal (IR): This step ensures the final removal of residual deleterious elements.
Product Precipitation: High-grade Mixed Rare Earth Carbonate (MREC) is recovered. OD6 Metals has successfully produced high-quality MREC of approximately 56% TREO (total rare earth oxides) and Mixed Rare Earth Hydroxide (MREH) of approximately 59% TREO.

This flowsheet optimization combines heap leaching, nanofiltration, ion exchange, and impurity removal processes to create a more efficient and cost-effective operation. This approach eliminates several expensive processing steps such as leach tanks, thickening, clay washing, and solid-liquid separation.

Advantages of OD6 Metals’ Approach

OD6 Metals’ innovative heap leaching approach offers several key advantages:

Cost-Effectiveness: Heap leaching is generally a lower-cost method compared to conventional tank leaching. OD6 Metals’ Managing Director, Brett Hazelden, has stated that the company’s downstream steps are the “most capital-efficient and operationally simple route” to advance the value output of Splinter Rock.
Scalability: The heap leaching process only requires a “modular, scalable construction,” eliminating the need for large leach tanks and complex separation circuits.
Environmental Benefits: OD6 Metals’ process reduces energy consumption and water usage compared to traditional methods. The company’s nanofiltration technology recovers a significant portion of hydrochloric acid for recycling, minimizing reagent use and plant size.
High-Quality Product: OD6 Metals’ process produces a higher-quality Mixed Rare Earth Carbonate (MREC) product with lower impurity levels, particularly uranium and thorium. This is crucial for market acceptance and product value.

Environmental Considerations and Mitigation

While heap leaching offers numerous advantages, it’s essential to address potential environmental concerns. These include:

Leachate Leakage: Ensuring the integrity of the impermeable base to prevent leaching solution from leaking into the surrounding soil and groundwater.
Acid Mine Drainage (AMD): Preventing the oxidation of sulfide minerals in the ore, which can generate AMD, a highly acidic and metal-rich solution.
Wildlife Impacts: Protecting wildlife from exposure to toxic chemicals in the leaching solution or contaminated water sources.
Soil Contamination: Preventing spills or leaks of leaching solution that can contaminate the soil.

OD6 Metals incorporates several measures to mitigate these risks:

Spent Heap Management: After leaching, heaps undergo neutralization and stabilization to prevent acid generation, with encapsulation systems to isolate any potentially reactive materials.
Water Circuit Design: Comprehensive water management systems capture and treat all contact water, with continuous monitoring to ensure compliance with discharge standards.
Progressive Rehabilitation: Concurrent reclamation of disturbed areas as operations advance, minimizing the active footprint and accelerating ecosystem restoration.

Market Implications and Strategic Advantage

The rare earth elements market is currently dominated by a few key players, with China being the largest producer and consumer of REEs. OD6 Metals’ innovative heap leaching process has the potential to disrupt this market by providing a cost-effective and environmentally responsible alternative for REE extraction.

A key benefit of OD6’s process innovations is the ability to produce a higher-quality Mixed Rare Earth Carbonate (MREC) product with lower impurity levels, particularly uranium and thorium. This is critically important for market acceptance and product value. Specifications for U/Th in MREC vary by customer, but OD6’s ability to achieve <0.001 wt% levels of both U and Th positions the company to meet even the most stringent market requirements of U < 2 ppm and Th < 5 ppm.

OD6 Metals is strategically positioned to capitalize on the growing demand for REEs and the increasing focus on supply chain diversification. The company is actively engaging with potential offtake partners and expanding its network of potential high-value downstream customers across North America, Europe, and Asia.

The Future of Rare Earth Extraction

OD6 Metals’ innovative heap leaching approach represents a significant step forward in rare earth extraction. By combining cost-effectiveness, scalability, and environmental responsibility, the company is poised to become a leading player in the critical minerals sector. As the demand for REEs continues to grow, OD6 Metals’ technology could play a crucial role in ensuring a sustainable and secure supply of these essential elements.

Open Questions:

How will OD6 Metals’ heap leaching process perform at full commercial scale?
What impact will OD6 Metals’ technology have on the overall rare earth elements market?
How will regulations and enforcement surrounding rare earth mining evolve to ensure responsible environmental practices?