Geochemistry of barium ions associated with biogenic manganese oxide nanoparticles generated by a fungus strain: Implications for radium sequestration in uranium mill tailings
Journal
Gondwana Research
Journal Volume
110
Start Page
270
End Page
282
ISSN
1342-937X
Date Issued
2022-10
Author(s)
Yokoo, Hiroki
Oki, Takumi
Uehara, Motoki
Dwi Winarni, Ilma
Yamaji, Keiko
Fukuyama, Kenjin
Ohara, Yoshiyuki
Ohnuki, Toshihiko
Hochella, Michael F.
Abstract
Biogenic Mn oxides are reactive and ubiquitous in many Earth surface environments, yet their role in radionuclide sequestration at U mill-tailings sites still require an improved understanding at the nano- and molecular-scales. This study concerns the uptake of Ba, utilized as a safe and chemically appropriate surrogate for radioactive Ra, by biogenic Mn oxides produced by a fungal species, Coprinopsis urticicola, isolated from the mine water of the Ningyo-toge U mine, Okayama, Japan. The biogenic Mn oxides were identified as birnessite nanocrystals <10 nm in width having many vacancy sites in the MnO6 octahedral layers. Ba2+ adsorption experiments using biogenic birnessite were conducted at pH 6.00 ± 0.02 with the initial Ba concentrations ranging from 10–8 to 10–3 mol/L. The apparent distribution coefficient, Kd, was calculated to be 103.8 L/g for biogenic birnessite, which is comparable to the apparent Kd of Ra in the mill tailings pond at Ningyo-toge. Both in adsorption and coprecipitation experiments, extended X-ray absorption fine edge structure analysis of Ba L3 edge revealed that the Ba atom forms an inner-sphere complex with O atoms of the MnO6 layer. A slightly greater coordination number for coprecipitated Ba may be attributed to the formation of Ba[sbnd]O binding to the newly overlying MnO6 layer during coprecipitation. Static desorption experiments for 7 days reveal that the steady-state release rate of adsorbed Ba is ∼1.4 times faster than that of the coprecipitated Ba, when the Ba concentration in the initial loading solution was ∼10–8 mol/L, indicating that the release of intercalated (coprecipitation) Ba to solution is retarded. The present study demonstrates the importance of fungus-generated Mn oxides as an efficient absorber of Ba2+, and likely Ra2+, among soil compounds in U mill-tailings. This may be applicable to other contaminated sites due to the ubiquitous occurrence of fungi in the environment.
Subjects
Barium adsorption
Biogenic Mn oxides
Coprinopsis urticicola fungus
Radium
Uranium mill tailings
Publisher
Elsevier BV
Type
journal article