Thermodynamic modeling of the sorption of radioelements onto cementitious materials
- AEA Technology, Harwell (United Kingdom)
A model has been developed for the sorption of radioelements onto cementitious materials based on the diffuse-layer modeling approach. The model assumes that silicon sites (>SiOH) and calcium sites (>CaOH) dominate the surface chemistry and the sorption of radioelements onto the cementitious materials. Both types of site may undergo surface protonation and deprotonation reactions. Cement-based systems vary greatly in their chemistry depending on their calcium-to-silicon molar ratio, and the corresponding variation in the surface chemistry has been incorporated by allowing sorption of calcium ions onto silicon sites. This process results in a change from a silica-type surface, at very low calcium-silicon ratios, to a calcium hydroxide-type surface for high-calcium cement-based materials. The predicted variation in the surface chemistry is consistent with literature data on measured zeta potentials of cements. The model has been applied successfully to describe the sorption of simple caesium and iodide ions at varying calcium-silicon ratios. In a Nirex repository for low and intermediate level wastes, a high-calcium cementitious backfill would be specified. This model has allowed a consistent interpretation of experimental data for sorption of key radioelements, including uranium and plutonium, onto the backfill, under saline and non-saline conditions.
- OSTI ID:
- 264450
- Report Number(s):
- CONF-951155-; ISBN 1-55899-315-0; TRN: 96:016595
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 27 Nov - 1 Dec 1995; Other Information: PBD: 1996; Related Information: Is Part Of Scientific basis for nuclear waste management 19; Murphy, W.M. [ed.] [Southwest Research Inst., San Antonio, TX (United States)]; Knecht, D.A. [ed.] [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States)]; PB: 957 p.; Materials Research Society symposium proceedings, Volume 412
- Country of Publication:
- United States
- Language:
- English
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