Iron oxyhydroxide colloid formation by gamma-radiolysis

Yakabuskie, Pamela A.; Keech, Peter G.; Botton, Gianluigi A.; Guzonas, David; Wren, J. C.

doi:10.1039/c1cp20084d

Cited by 37 publications

(29 citation statements)

References 25 publications

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“…For instance, irradiation led to Fe(III) reduction in a range of materials, including clays and goethite (28,(30)(31)(32). On the other hand, irradiation induced oxidation of Fe in steel and aqueous Fe(II) solutions led to the generation of the Fe(II)/(III) oxides lepidocrocite, maghemite, and magnetite (33,34). Such changes to the oxidation state of Fe may have important implications for the bioavailability of Fe(III) for microbial respiration.…”

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confidence: 99%

The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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cMicrobial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h ؊1 for 8 weeks all displayed NO 3 ؊ and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h ؊1 treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h ؊1 treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO 3 ؊ , Fe(III), or SO 4 2؊ reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h ؊1 -treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h ؊1 and 30-Gy h ؊1 treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation. In many countries, including the United Kingdom, the current policy for the long-term disposal of intermediate-level radioactive waste is to a deep geological disposal facility (GDF). In UK disposal concepts for higher-strength rocks and lower-strength sedimentary rocks, much of the intermediate-level radioactive waste is immobilized with a cementitious grout in stainless steel containers that are then surrounded with a cementitious backfill prior to closure of the facility (1). The vicinity of a GDF will not be a sterile environment, and microbial activity in the surrounding geosphere could have important implications for the evolution of biogeochemical processes, including microbial gas generation and utilization, microbially induced corrosion of waste containers and contents, and the mobility of radionuclides (2). In addition, there will be elevated concentrations of potential electron donors in and around the repository, including organics from the degradation of cellulose in the waste (3), and also molecular hydrogen from the radiolysis of water and the anaerobic corrosion of steel drums (4). Indeed, the availability of alternative electron acceptors will likely not be limited, since nitrate can be present in nuclear waste materials (5), and Fe(III) will be present due to aerobic corrosion of waste components and engineered infrastructure during the operational phase of the GDF.The stimulation of an Fe(III)-reducing community due to an increase in electron donors and acceptors is of particular interest since this may promote the reduction and precipitation of redoxactive radionuclides via the production of biogenic Fe(II)-bearing phases (2, 6). Indeed, many key Fe(III)-reducin...

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confidence: 99%

The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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“…The analysis for Cr III is only able to quantify the Cr III that is dispersed in the solution sample extracted from the test vial by syringe. Incomplete mass balance was reproducible and also observed in all of our studies on radiation-induced metal-oxide nanoparticle formation [29][30][31]. Thus, we believe that the incomplete mass balance originates from a physical process such as adsorption of Cr VI on particle surfaces, and not due to experimental errors, see further discussion in Section 4.Stage II refers to the short transition period between Stages I and III and lasts for only a few minutes.…”

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confidence: 69%

Radiation-Induced Formation of Chromium Oxide Nanoparticles: Role of Radical Scavengers on the Redox Kinetics and Particle Size

Alrehaily

Wren

2015

J. Phys. Chem. C

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The formation of Cr 2 O 3 nanoparticles by gamma irradiation of dichromate solutions was investigated in the presence of radical scavengers, t-butanol, nitrous oxide and dissolved oxygen.The concentrations of Cr VI and Cr III species and the chemical composition and sizes of particles that were formed were measured as a function of irradiation time. A mechanism is proposed that is consistent with the observed effects of scavengers on the kinetics of reduction of Cr VI in solution to solid Cr III , and the final size of Cr 2 O 3 nanoparticles that are formed. The chromium reduction occurs in three stages: Stage I involves homogeneous aqueous reduction of Cr VI (aq) to Cr III (aq) followed by spontaneous condensation of Cr(OH) 3 , providing nucleation sites onto which Cr VI and Cr III co-precipitate and form mixed Cr VI /Cr III oxide/hydroxide particles. In Stage II the aqueous reduction of Cr VI (aq) and Cr III (aq) reaches steady state but the adsorption of Cr VI continues, growing the mixed Cr VI /Cr III oxide/hydroxide particles. Stage 3 involves the solidstate conversion of Cr VI and Cr III and the particles slowly convert from a mixed Cr VI /Cr III oxide/hydroxide to Cr(OH) 3 and then to Cr 2 O 3 . Adding a radical scavenger in solution affects the kinetics of particle formation and growth at different stages differently. This information can be used to tailor the final sizes of particles.

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“…Nitrate and nitrite ions can both participate in a series of redox reactions with reducing (e.g., • e aq À , • O 2 À ) and oxidizing (e.g., • OH, HO 2 • ) species, (R41) to (R46). More importantly, one of their intermediate products, NO 2 • , disproportionates to NO 3 À and NO 2 À at a fast rate. This series of reactions establishes a pseudocatalytic cycle between NO 3 À and NO 2 À .…”

Section: Radiolysis Of Aqueous Solutionsmentioning

confidence: 99%

Long-Term γ-Radiolysis Kinetics of NO₃⁻ and NO₂⁻ Solutions

2011

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Radiolysis kinetics in NO(3)(-) and NO(2)(-) solutions during γ-irradiation were studied at an absorbed dose rate of 2.1 Gy·s(-1) at room temperature. Air- or argon-saturated nitrate or nitrite solutions at pH 6.0 and 10.6 were irradiated, and the aqueous concentrations of molecular water decomposition products, H(2) and H(2)O(2), and the variation in the concentrations of NO(3)(-) and NO(2)(-) were measured as a function of irradiation time. The experimental data were compared with computer simulations using a comprehensive radiolysis kinetic model to aid in interpretation of the experimental results. The effect of nitrate and nitrite, present at concentrations below 10(-3) M, on water radiolysis processes occurs through reactions with the radical species generated by water radiolysis, (•)e(aq)(-), (•)O(2)(-), and (•)OH. The changes in H(2) and H(2)O(2) concentrations observed in the presence of nitrate and nitrite under a variety of conditions can be explained by a reduction in the radical concentrations. The kinetic analysis shows that the main loss pathway for H(2) is the reaction with (•)OH and the main loss pathways for H(2)O(2) are reactions with (•)e(aq)(-) and (•)OH. Nitrate and nitrite compete for the radicals leading to an increase in the concentrations of H(2) and H(2)O(2). Post-irradiation measurements of H(2), H(2)O(2), NO(2)(-) and NO(3)(-) concentrations can be used to calculate the radical concentrations and provide information on the redox conditions of the irradiated aqueous solutions.

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Iron oxyhydroxide colloid formation by gamma-radiolysis

Cited by 37 publications

References 25 publications

The Impact of Gamma Radiation on Sediment Microbial Processes

The Impact of Gamma Radiation on Sediment Microbial Processes

Radiation-Induced Formation of Chromium Oxide Nanoparticles: Role of Radical Scavengers on the Redox Kinetics and Particle Size

Long-Term γ-Radiolysis Kinetics of NO₃⁻ and NO₂⁻ Solutions

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Iron oxyhydroxide colloid formation by gamma-radiolysis

Cited by 37 publications

References 25 publications

The Impact of Gamma Radiation on Sediment Microbial Processes

The Impact of Gamma Radiation on Sediment Microbial Processes

Radiation-Induced Formation of Chromium Oxide Nanoparticles: Role of Radical Scavengers on the Redox Kinetics and Particle Size

Long-Term γ-Radiolysis Kinetics of NO3− and NO2− Solutions

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Long-Term γ-Radiolysis Kinetics of NO₃⁻ and NO₂⁻ Solutions