Montmorillonite colloids: II. Colloidal size dependency on radionuclide adsorption

Abstract

Bentonite is a strong radionuclide (RN) adsorbent. As a consequence, it is proposed as one of the engineered safety barriers in many concepts of nuclear waste disposal in granite formations. Nevertheless, in contact with groundwater of low ionic strength, montmorillonite colloids may be released from the bentonite buffer and transported towards the biosphere. During the transport of colloids in bedrock fractures, size separation of clay colloids may occur, that may potentially also affect the RN mobility. In this work, the RN adsorption (Th(IV), U(VI), Np(V), Tc(VII) and Pu(IV)) onto size fractionated montmorillonite colloids was studied in a synthetic, carbonated groundwater. We combined batch adsorption experiments and geochemical modelling. U(VI), Np(V) and Tc(VII) did not adsorb to the montmorillonite colloids in the synthetic groundwater. Adsorption of Th(IV) and Pu(IV) was strong but, within experimental uncertainties, not significantly affected by the mean colloidal size. In this case, average K D values could in principle be used in reactive transport modelling. Montmorillonite clay colloids obtained by fractionation of the raw clay material but in the presence of organic matter during the initial separation step exhibited significantly reduced affinity for Th and Pu.

Modeling of Innovation Research Clusters in the Field of Radioactive Waste Utilization

“…The adsorption of Th (IV), U (VI), Np (V), Tc (VII), and Pu (IV) on fractionated fractions of montmorillonite in synthetic carbonated groundwaters was studied. Montmorillonite colloids obtained by fractionation of crude clay material in the presence of organic matter at the initial stage of separation, there is a significant decrease in the absorption of Th and Pu [20].…”

Nano-Montmorillonite Regulated Crystallization of Hierarchical Strontium Carbonate in a Microbial Mineralization System

“…Biomineralization refers to the process that an organism constructs a hierarchical structure based on inorganic minerals under certain environmental conditions [1,2,3,4,5]. This process is highly regulated by the biological environments that guide mineral nucleation and growth, including solution states, biomacromolecules, and substrates [6,7,8]. Although the main components of many mineralized tissues are the inorganic phases regulated by the upper biological environment during crystallization and growth.…”

LA-ICP-MS analysis of trace and rare-earth element distribution in calcite fracture fillings from Forsmark, Simpevarp and Laxemar (Sweden)

“…Ø 70.3 Highly variable REE content, mostly flat Chondrite normalized profile Highly variable REE content, significant LREE enrichment minerals(Kretzschmar and Schäfer 2005;Bouby et al 2008;Norrfors et al 2016) is widely observed in ground waters.…”