Rare Earth Exchanges

Seaweed-Based Solutions for Acid Mine Drainage: A New Frontier in Rare Earth Element Recovery

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Highlights

  • Portuguese scientists demonstrate how three seaweed species can effectively remove rare earth elements from acid mine drainage.
  • Living seaweed achieved up to 75% REE removal, concentrating elements up to 1400-fold compared to initial levels.
  • Research suggests seaweed-based remediation could transform environmental challenges into resource recovery opportunities.

A groundbreaking study led by Portugal-based scientists Thainara Viana, Nicole Ferreira, Eduarda Pereira, and Bruno Henriques investigate the use of seaweed to address the environmental and resource challenges posed by acid mine drainage (AMD). The study evaluates the ability of three seaweed species—Gracilaria sp., Ulva sp., and Fucus sp.—to remove rare earth elements (REEs) from AMD, positioning seaweed-based biotechnologies as a promising alternative for AMD treatment and resource valorization.

The recent study was published in the Science of the Total Environment (opens in a new tab).

Study Methodology

In this investigation looking at bioaccumulation vs. biosorption,  researchers compared living (bioaccumulation) and dried (biosorption) seaweed for REE removal from AMD, analyzing efficiency under original and pH-adjusted conditions.

Also under investigation were species and dosage.Gracilaria sp., Ulva sp., and Fucus sp. were tested for REE removal efficiency at different dosages.

Finally, analysis involved scanning electron microscopy (SEM-EDS) and Fourier-transform infrared spectroscopy (FTIR) as a means of examining  seaweed morphology and the chemical binding mechanisms.

What did the scientists find?

First the authors point to the efficiency of living seaweed. Bioaccumulation was more effective than biosorption, for instance, with Gracilaria sp. achieving REE removal rates up to 75% and Ulva sp. reaching 44% within 24 hours.

Living seaweed concentrated REEs up to 1400-fold compared to initial levels in another striking observation.

What about the role of polysaccharides?

Functional groups like sulphonates and carboxyls in seaweed cell walls were critical for binding REEs, as confirmed by FTIR analysis.

Other outcomes involved the measuring of pH adjustment impact.  Adjusting AMD pH to 5.0 effectively removed non-interest elements (e.g., Fe and Al) while preserving most REEs for removal by seaweed.

It turns out that seaweed dosage matters. Higher dosages of Gracilaria sp. and Ulva sp. improved REE removal, although diminishing returns were observed at excessive concentrations.

Also seaweed-based remediation can be seamlessly integrated into passive AMD treatment systems, such as wetlands, providing a low-cost, sustainable solution.

What are some study implications?  Limitations?

First, his innovative approach turns AMD from an environmental burden into a valuable resource that supports circular economy principles. Seaweed remediation offers a greener alternative to traditional REE extraction methods, which are resource-intensive and environmentally harmful.

However, challenges ensue, such as knowledge gaps. While promising, the long-term viability, scalability, and economic feasibility of seaweed-based systems require further research.

The study focuses primarily on AMD in controlled settings, leaving open questions about performance in diverse real-world environments, which open all sorts of implications.

Rare Earth Exchanges reviewed bias and assumptions inherent in the authors’ output.  The study emphasizes the promise of seaweed-based technologies without fully addressing economic barriers or potential competition from other advanced REE recovery methods.

Due to a confluence of factors and forces the study’s findings may not generalize to all REEs or other critical materials.

Conclusion

This study positions Gracilaria sp. and Ulva sp. as powerful tools for AMD remediation and REE recovery, offering a sustainable path to addressing critical mineral shortages. By integrating seaweed-based systems into current AMD treatment frameworks, industries can reduce environmental impacts while enhancing resource recovery. However, further exploration of scalability and real-world adaptability is essential for unlocking the full potential of this promising technology.

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