title: Chemical speciation and association of plutonium with bacteria, kaolinite clay, and their mixture.
abstract: We investigated the interactions of Pu(VI) with Bacillus subtilis, kaolinite clay, and a mixture of the two to determine and delineate the role of the microbes in regulating the environmental mobility of Pu. The bacteria, the kaolinite, and their mixture were exposed to a 4 x 10(-4) M Pu(VI) solution at pH 5.0. The amount of Pu sorbed by B. subtilis increased with time, but had not reached equilibrium in 48 h, whereas equilibrium was attained in kaolinite within 8 h. After 48 h, the oxidation state of Pu in the solutions exposed to B. subtilis and the mixture had changed to Pu-(V), whereas the oxidation state of Pu associated with B. subtilis and the mixture was Pu(IV). Exudates released from B. subtilis reduced Pu(VI) to Pu(V). In contrast, there was no change in the oxidation state of Pu in the solution or on kaolinite after exposure to Pu(VI). Scanning electron microscopy-energy dispersive spectrometry analysis indicated that most of the Pu in the mixture was associated with B. subtilis. These results suggest that Pu-(IV) is preferably sorbed to bacterial cells in the mixture and that Pu(VI) is reduced to Pu(V) and Pu(IV).
authors.affiliation: Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan. ohnuki.toshihiko@jaea.go.jp
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ohnuki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yoshida
authors.forename: Takuo
authors.initials: T
authors.lastname: Ozaki
authors.forename: Naofumi
authors.initials: N
authors.lastname: Kozai
authors.forename: Fuminori
authors.initials: F
authors.lastname: Sakamoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Nankawa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Arokiasamy J
authors.initials: AJ
authors.lastname: Francis
mesh_terms: D000327:Adsorption; D001412:Bacillus subtilis / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D007616:Kaolin / Q000737:chemistry*; D010084:Oxidation-Reduction; D011005:Plutonium / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007616:Kaolin; D011005:Plutonium