Sorption of Uranium(VI) on Opalinus Clay in Absence and Presence of Humic Acid

For nuclear waste disposal in geological formations, possible host rocks in Germany are salt rock (Gorleben), granite rock and clay. Currently, intense examinations on natural clay are taking place in a joint project funded by the Federal Ministry of Economics and Technology. An important part of this is the investigation of sorption and migration processes resulting from the actinide interaction with natural clay and the determination of the influence of clay organic matter on these processes. In this regard, the sorption of uranium(VI) on natural clay is examined. Furthermore, the influence of organic matter, such as fulvic acids (FA) and humic acids (HA), known for their ability to bind metal ions, is investigated.
Here some characteristics of the natural clay, opalinus clay from Mont Terri (Switzerland), and the synthetic opalinus clay pore water are shown. The speciation of uranium(VI) in this pore water in the absence and presence of HA is presented. The sorption of uranium(VI) in the absence and presence of HA onto opalinus clay and onto the reference clay mineral kaolinite is compared .