Ce, Gd and Yb accumulation in microalgae: an L-edge XAS study

Area of Science:

• Biotechnology
• Environmental Science
• Chemistry

Background:

• Rare earth elements (lanthanides) exhibit similar chemical properties, complicating their extraction and separation.
• Biological processes offer potential for selective elemental interactions.
• Microalgae can accumulate specific elements, presenting a novel approach for rare earth recovery.

Purpose of the Study:

• To investigate the interaction of cerium (Ce), gadolinium (Gd), and ytterbium (Yb) with the microalga Chlamydomonas reinhardtii.
• To explore the potential of microalgae for the selective separation of rare earth elements.
• To characterize the chemical forms of lanthanides bound to microalgae.

Main Methods:

• Utilized X-ray absorption spectroscopy (XAS), including X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS).
• Analyzed lanthanide interactions at the Ce L3-edge, Gd L3-edge, and Yb L3-edge.
• Characterized lanthanide-phosphate compounds formed by Chlamydomonas reinhardtii.

Main Results:

• All three lanthanides (Ce, Gd, Yb) reacted with the algae to form phosphate compounds, irrespective of phosphate granule presence.
• CePO4 formation was identified using XANES.
• The structures of GdPO4 and YbPO4 were elucidated using EXAFS analysis.

Conclusions:

• Chlamydomonas reinhardtii interacts with lanthanides to form phosphate compounds.
• Microalgae demonstrate potential for selective rare earth element removal from aqueous solutions.
• This biological approach could offer an environmentally friendly alternative for lanthanide recovery.