Mapping Rare Earth Element Distribution in MSWI Ash Using Physical Separation and Sequential Extraction

Area of Science:

• Environmental Science
• Geochemistry
• Materials Science

Background:

• Growing global demand for rare earth elements (REEs) necessitates exploring secondary resources.
• Anthropogenic waste streams, such as municipal solid waste incineration (MSWI) ash, are potential sources of REEs.

Purpose of the Study:

• To characterize the distribution and speciation of REEs in Korean MSWI bottom ash (BA) and fly ash (FA).
• To investigate REE behavior across different particle sizes and magnetic fractions.
• To assess REE leachability and chemical associations within the ash matrix.

Main Methods:

• Particle size fractionation and magnetic separation of BA and FA samples.
• Sequential extraction analysis to determine REE speciation and lability.
• Inductively coupled plasma optical emission spectrometry (ICP-OES) for elemental composition.
• X-ray diffraction (XRD) for mineral phase identification.

Main Results:

• REEs are enriched in the magnetic fractions of both BA and FA.
• Higher REE concentrations were observed in coarser particle fractions.
• Light rare earth elements (LREEs) were predominant across all particle sizes.
• Sequential extraction revealed that REEs are primarily associated with stable mineral phases, with limited labile fractions.

Conclusions:

• MSWI ash contains significant amounts of REEs, particularly in magnetic and coarser fractions.
• The majority of REEs are bound within stable mineral phases, influencing their potential for mobilization.
• Findings provide a foundation for understanding REE recovery and management strategies from waste streams.