Uranium (VI) sorption onto selected mineral surfaces: Key geochemical parameters

Conference · Tue Oct 01 04:00:00 UTC 1996

OSTI ID:370465

Pabalan, R T; Bertetti, F P; Prikryl, J D; Turner, D R ^[1]

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1. Southwest Research Institute, San Antonio, TX (United States)

Batch U(VI) sorption experiments were conducted using quartz, montmorillonite, clinoptilolite, and {alpha}-alumina to determine the key geochemical parameters that influence sorption onto mineral surfaces. The experiments were done at different initial U concentration, pH, M/V, and ionic strength, and at ambient and elevated PCO{sub 2} (10{sup -3.5} and 10{sup -2.0} atm, respectively). The results show that U(VI) sorption on all the minerals studied reaches a maximum at near-neutral pH ({approximately}6.3-6.8) and decreases sharply towards more acidic or alkaline conditions. The pH range where U sorption occurs corresponds to the predominance field of aqueous monomeric U(VI)-hydroxy complexes. Sorption is inhibited at high pH and PCO{sub 2} due to formation of aqueous U(VI)-carbonate complexes. For montmorillonite and clinoptilolite, ion-exchange was suppressed due to the relatively high ionic strength of the solutions. Surface charge properties of the sorbent are inferred to be relatively unimportant factors in U(VI) sorption. Sorption data plotted in terms of K{sub d} show that M/V ratio has little influence on the distribution of U(VI) between the solid and aqueous phases. Modeling of the sorption behavior of U(VI) was performed using a surface complexation approach (Diffuse-Layer Model).

• OSTI ID: 370465
• Report Number(s): CONF-960376--
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADSORPTION
CLINOPTILOLITE
MINERALS
MONTMORILLONITE
PH VALUE
QUARTZ
RADIONUCLIDE MIGRATION
SOILS
SORPTIVE PROPERTIES
SURFACE PROPERTIES
URANIUM