title: Migration of75Se(IV) in crushed Beishan granite: Effects of the iron content.
abstract: The diffusion of selenite (labeled with75Se) in compacted Beishan granite (BsG) was investigated using the in-diffusion capillary method at pH values from ∼2.0 to ∼11.0 under oxic and anoxic conditions. The results indicate that the apparent diffusion coefficient (Da) values of selenite in BsG always reached the minimum at approximately pH 5. Unexpectedly, the Davalues under oxic conditions are nearly one order of magnitude lower than those under the anoxic conditions. Further characterization reveals the existence of redox-sensitive Fe(II)-containing components, which can be responsible for the great difference in Davalues. Fe(2p) X-ray photoelectron spectroscopy (XPS) results show that more Fe(III)-oxyhydroxide coating is formed on the granite's surface under aerobic conditions than is formed under anaerobic conditions. Correspondingly, Se(3d) spectra indicate that more selenium is sorbed under oxic conditions, and the sorbed amount always reached the maximum at pH values from ∼4 to ∼5. A linear combination fit of X-ray absorption near edge structure (XANES) spectroscopy data revealed that Se(0) was formed under anoxic condition and that selenite preferred to form inner-sphere complexes with Fe(III)-oxyhydroxide. Overall, this study indicates that natural Fe-bearing minerals can greatly attenuate selenite diffusion and the retardation would be enhanced under aerobic conditions.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Jiangang
authors.initials: J
authors.lastname: He
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Ma
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Mingliang
authors.initials: M
authors.lastname: Kang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Chunli
authors.initials: C
authors.lastname: Wang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Nie
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Fundamental Science Laboratory on Radiochemistry & Radiation Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China. Electronic address: liucl@pku.edu.cn.
authors.forename: Chunli
authors.initials: C
authors.lastname: Liu
keywords: Beishan granite; Diffusion; Fe(III)-oxyhydroxides; Nuclear waste disposal; Selenite