Waste Sargassum Seaweed as a Sustainable Resource for Rare Earth Element Recovery

Abstract

Rare earth elements (REEs) are vital for advanced technologies, yet their supply is limited and geographically concentrated, highlighting the need for alternative sources. Since 2011, massive pelagic Sargassum blooms have produced millions of tons of biomass along coastlines, posing environmental challenges but offering untapped resource potential. Here, we demonstrate an ecofriendly “algal mining” approach, repurposing as a renewable biosorbent for REE recovery, offering a waste-to-resource pathway aligned with circular economy principles. We present the first direct comparison of REE uptake in fresh and dried Sargassum filipendula across concentrations from 0.1 to 600 μM. Fresh biomass showed superior accumulation at low, environmentally relevant concentrations (0.1–11 μM) than dried biomass, while uptake was comparable at higher levels (100–600 μM). S. filipendula sequestered up to 77,299 μM ytterbium, with Langmuir isotherm modeling indicating high adsorption capacities and binding affinities, particularly for heavy REEs. Compared with activated carbon, S. filipendula maintained superior performance under high salinity and variable pH conditions that reduce the conventional adsorbent efficiency. These findings support the S. filipendula as a marine-adapted, scalable biosorbent that can simultaneously mitigate the impacts of coastal Sargassum blooms and contribute to the sustainable supply of critical materials for renewable energy and advanced technologies.