Abstract
Abstract Bentonite, a natural clay, is a promising candidate to be used as a buffer/backfill material in the geological disposal systems for management of high level waste (HLW). Fe released due to corrosion of canister/overpack may result in alteration of Na-montmorillonite (Na-Mt), present in bentonite, to Fe-montmorillonite (Fe-Mt) in a span of several years after the emplacement of vitrified HLW in deep geological repositories. For realistic performance assessment, it is essential to understand the sorption behavior of altered Mt with regard to the radionuclides present in HLW. Cs is one of the high-yield (137Cs t1/2 = 30.1 y, 6%) and long-lived (135Cs t1/2 = 2 × 106 y) fission products in spent fuels. The objective of present study is to understand the effect of various parameters, viz., time (0–48 h), pH (3.0–9.0), ionic strength (0.001–1 M) [Cs(I)] (10−10–10−3 M) and Fe dissolution on sorption behavior of Cs(I) on Fe(II)-Mt through batch sorption experiments. Fe(II)-Mt was synthesized by reducing Fe(III)-Mt using ascorbic acid as reducing agent in N2 atmosphere. The near-constancy in Cs(I) sorption on Fe(II)-Mt with pH (≥4), and decrease with increasing ionic strength, illustrate the ion exchange as dominant mode of Cs(I) sorption. Further, Cs(I) sorption isotherm on Fe(II)-Mt is found to be linear. The estimation of dissolved iron in the supernatant of Fe(II)-Mt suspensions demonstrated that dissolved Fe decreased with increase in pH and increased with increase in ionic strength. Moreover, the Fe2+/Fetotal ratio determined in all experiments was close to unity, thereby depicting that Fe(II) did not oxidize to Fe(III), except when suspension pH was ≥ 5.5. For comparison, Cs(I) sorption was also studied on Na(I)-Mt and compared with that on Fe(III)-Mt. Surface complexation modeling of Cs(I) sorption on the three clay minerals, viz., Na-Mt, Fe(II)-Mt and Fe(III)-Mt, has been successfully carried out.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
