Element Case Studies: Rare Earth Elements

The growing demand of strategic resources, e.g. rare earth elements (REEs), for development of modern technologies has spurred an increase in mining activities and consequently a release of REEs into the environment, posing a potential threat to human health. Phytoremediation, regarded as an in situ and low-cost means to remediate polluted soils, uses the growth and harvest of hyperaccumulator plants that take up high concentrations of metals in their shoots, allowing metal removal from contaminated soil (phytoextraction) or commercial production of high-value metals (phytomining). In this chapter, we review the discovery of REE hyperaccumulators worldwide, particularly focusing on the fern species Dicranopteris dichotoma that preferentially takes up light REEs. Though less understood, mechanisms of REE uptake, translocation, and distribution in hyperaccumulator plants are also discussed. Finally, taking D. dichotoma as an example, we estimate the phytomining potential for REEs using this species, based on its biomass production, REE concentrations in the ash, and current market prices of REEs.