Characterization of thorium binding by sequential extractions in uranium tailings of Schneckenstein, Germany

Abstract

The chemical binding forms of Thorium in uranium tailings of Schneckenstein sites were investigated regarding a remediation strategy. A modified Tessier’s seven steps sequential extraction procedure was used for the fractionation of different classes of thorium species present in the sediments. The consecutive steps included leaching of the water-soluble thorium, liberation of thorium from exchange sites on inorganic soil constituents, extraction of carbonates bound species, release of specifically adsorbed thorium on manganese and iron oxides, removal of species associated with insoluble soil organic matter and sulfides and finally extraction of metal intrinsic in the soil matrix present in the structure of primary and secondary minerals. The results indicate that no thorium in the mobile phases. An appreciable amount of its total content is in the moderately reducible phase. Whereas, from 73 to 92% of the thorium is attached to clays and partly to resistant minerals.