Microalgae-mediated recovery of rare earth elements: mechanisms, strategies, and circular bioeconomy perspectives

Rare earth elements (REEs) are critical strategic resources for renewable energy, advanced manufacturing, electronic devices, and national defense. However, conventional REEs mining and recycling are often associated with high energy consumption, intensive chemical use, and substantial environmental burdens. Biological recovery is regarded as an important alternative for green REEs recycling. Recently, microalgae-mediated REEs has attracted significant attention due to its high absorption efficiency and environmental friendliness. However, compared with bacterial and fungal systems, microalgae-mediated REEs recovery remains relatively underexplored, and its potential application value requires further investigation. This review systematically summarizes recent progress in microalgae-based REEs recovery from secondary resources and integrates current knowledge into a unified mechanistic framework covering bioleaching, biosorption, bioaccumulation, and biomineralization. It describes the roles of microalgae in REEs release, surface adsorption, intracellular accumulation, and stable immobilization. The review further highlights the unique advantages of microalgae, including photosynthetic growth, strong surface reactivity, environmental adaptability, carbon fixation capacity, and potential integration with wastewater treatment and biomass valorization. In addition, this review identifies key bottlenecks limiting practical application, such as low biomass productivity, insufficient selectivity, incomplete mechanistic understanding, and scale-up challenges. Future research directions are proposed, including mechanistic elucidation, strain engineering, algae–bacteria consortia, immobilization technologies, and process optimization. Overall, this review provides a systematic framework for understanding and advancing microalgae-mediated green REEs recovery and offers new perspectives for REEs recycling and circular bioeconomy strategies.