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N. L. Banik, R. Buda, S. Bürger, Jens Volker Kratz, N. Trautmann
Sorption of tetravalent plutonium and humic substances onto kaolinite
Keywords: Plutonium, Oxidation state, Kaolinite, Sorption, desorption
The sorption of tetravalent plutonium onto kaolinite, a clay mineral, has been studied as a function of pH. The sorption studies have been performed by batch experiments under aerobic and anaerobic conditions (glove box). A pH range of 0–11 has been investigated with plutonium concentrations of 3.5×10-7−6.9×-9 M and a solid phase concentration of 4 g/L. A sorption edge at about pH=1 and maximum sorption around pH=8.5 has been found under aerobic and anaerobic conditions. In the presence of CO2 at pH>8.5, the sorption of plutonium is decreased due to the formation of soluble carbonate complexes. This is supported by speciation calculations for Pu(IV)-hydroxo-carbonate species in aqueous solution. Depending on the pH, 1%−10% of the sorbed plutonium is desorbed from the kaolinite and released into the fresh solution. For comparison with the behavior of Pu(IV), the sorption of the redox-stable Th(IV) onto kaolinite has also been investigated. Furthermore, the sorption of humic substances (HS) onto kaolinite has been studied as a function of pH and for varying concentrations of HS as a prerequisite to understand the more complex ternary system: plutonium, humic substances, and clay. It has been found that the sorption of Aldrich humic acid onto kaolinite is generally higher than that for Gorleben fulvic acid.
Radiochimica Acta, Oldenbourg Wissenschaftsverlag
Print ISSN: 0033-8230
Volume: 95, 10/2007
Pages: 569 - 575