263: Mechanisms of critical mineral retention in Sargassum

Abstract: Rare-earth elements (REEs) are increasing in demand as they become more frequently used in consumer electronics and specialized technology. However, the REE supply cannot keep pace with demand, so efforts have been made to find alternative sources. An underutilized alternative source for REEs is acid mine drainage. Many current methods of REE extraction and separation are unsuitable at the low pHs found in these drainages. REE extraction from acid mine drainage can be performed through the aid of the brown seaweed (Sargassum sp.) Sargassum sp. is composed of two primary polysaccharides: alginate and fucoidan. Alginate makes up the largest percentage of the polysaccharides and is expected to be the driving factor in metal retention within the seaweed. However, preliminary data shows metal retention in the Sargassum that cannot be accounted for based on the pKa of the carboxylate groups of alginate. To investigate the molecular origin of Sargassum sp. metal chelation, we selectively extracted different components (e.g. alginate, denatured proteins) and evaluated metal binding with the extracted components individually, and the remaining biomass. By determining the individual contributions of each material, we aim to deconvolute the complex metal-binding mechanism of Sargassum sp. The exploration of mechanisms behind REE retention in seaweed may lead to further development of novel ways to separate REEs from complex solutions.