Sorption of cobalt(II) on soil: effects of birnessite and humic acid

Time-Resolved Investigation of Cobalt Oxidation by Mn(III)-Rich δ-MnO2Using Quick X-ray Absorption Spectroscopy

“…While in Co_0.20 there is aqueous Co that can sorb to newly formed sites, in Co_0.05, where no Co 2+ remains in solution, surface-bound Co 2+ must migrate from initial sorption sites at the particle edges to the basal surface. This apparent migration of surface-bound Co 2+ to newly formed vacancies may occur due to mineral dissolution and reprecipitation, particle growth, or due to the flipping of edge-bound Co 2+ onto a vacancy formed near the edge sites. , We expect these processes to be kinetically hindered and thus explain the slow uptake of Co by Mn oxides observed in natural and lab-based samples over time scales of days to months. ,,,, …”

“…Cobalt sorption and oxidation by Mn III _δ-MnO 2 passed through a fast reaction step, which is consistent with previous studies using synthetic Mn oxides and soils containing Mn oxides. 16,18,51 Within 10 min, 88% (0.04 mol Co mol −1 Mn) and 55% (0.11 mol Co mol −1 Mn) of the total Co added to the slurry was sorbed in Co_0.05 and Co 0.20, respectively, with about 50% of the Co present as Co 3+ . Shell-by-shell fits of the EXAFS spectra acquired at t < 10 min resulted in low CNs for the Co 2+,3+ -Mn shells.…”

“…32,54 We expect these processes to be kinetically hindered and thus explain the slow uptake of Co by Mn oxides observed in natural and lab-based samples over time scales of days to months. 20,30,51,55,56 Oxidizing Capacity of Mn(III)-Rich δ-MnO 2 . After 10 min of reaction, about 50% of the sorbed Co was oxidized at the edges of Mn III _δ-MnO 2 to yield Co 3+ loadings of 0.02 and 0.05 mol Co 3+ mol −1 Mn in Co 0.05 and Co 0.20, respectively.…”

Polymer–Inorganic Coatings Containing Nanosized Sorbents Selective to Radionuclides. 2. Latex/Tin Oxide Composites for Cobalt Fixation

“…This determines a sustained interest to the fate of cobalt radionuclides in the environment, sorption/desorption on soil components, and bioavailability. 1,4,5 Independently of which strategy will be used for remediation of a radioactively contaminated site, it is imperative to eliminate or reduce migration of the radionuclides until cleanup is completed or until the radiation has decayed back to acceptable levels. 6 In order to prevent radionuclides spreading from a contaminated surface with aerosols, application of polymeric or emulsion fixatives (dust suppressors) became a general practice after nuclear accidents.…”

“…Cobalt radionuclides are strong γ-emitters, whose release from the sealed sources poses a serious health risk for humans and animals. This determines a sustained interest to the fate of cobalt radionuclides in the environment, sorption/desorption on soil components, and bioavailability. ,, …”