Rare Earth Elements recovery from bauxite by biosorption onto Galdieria sulphuraria: a challenging case of study

This paper describes a preliminary study on the recovery of Rare Earth Elements (REEs) from bauxite aqueous suspensions by biosorption onto Galdieria sulphuraria, a red microalga belonging to Cyanidiophyte (Rhodophyta) class. REEs are strategic commodities in many countries, and they are a valuable resource for the growing modern technology industry, owing to their unique magnetic, phosphorescent, and catalytic properties. There is an increasing request of REEs for a wide variety of high-tech and strategic applications. As is well known, developing environmentally friendly and economic approaches for REEs recovery is crucial given the increasing demand and potential environmental impacts of traditional mining methods. Recovering REEs using biosorption onto G. sulphuraria offers a promising approach due to the organism’s ability to tolerate harsh conditions and high metal concentrations. This approach posed a challenge due to the commonly low fraction of REEs in bauxite, which is much lower than the concentrations of aluminum and iron. The experimental procedure defined in this work consists of adsorption-desorption cycles, onto a reusable biomass, with a recovery yield of 5–30 % (w/w), combining biological and chemical processes to enhance recovery efficiency while potentially minimizing environmental impact.