Incorporation of Radioactive Contaminants into Pyroaurite-Like Phases by Electrochemical Synthesis

Roh, Yul; Lee, S.Y.; Elless, Mark P.; Foss, J. E.

doi:10.1346/ccmn.2000.0480213

Cited by 47 publications

(23 citation statements)

References 19 publications

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“…The Mn(IV) oxide was prepared as described by Lovley and Phillips (29) (45). The effects of temperatures (25 to 75°C), pH (6.5 to 9.6), and salinity (0.05 to 7% NaCl) on microbial Fe(III) reduction and mineral formation were also examined using an Fe(III) oxyhydroxide (70 mM) as an electron acceptor and lactate (10 mM) as an electron donor.…”

Section: Methodsmentioning

confidence: 99%

Isolation and Characterization of Metal-Reducing Thermoanaerobacter Strains from Deep Subsurface Environments of the Piceance Basin, Colorado

Roh

Liu

Huang

et al. 2002

Appl Environ Microbiol

144

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Five bacterial strains were isolated from anaerobic enrichment cultures that had originated from inoculations with samples collected from the deep subsurface environments of the millions-of-years-old, geologically and hydrologically isolated Piceance Basin in Colorado. Small-subunit rRNA gene-based analyses indicated that all of these bacteria were closely related to Thermoanaerobacter ethanolicus, with similarities of 99.4 to 99.5%. Three isolates (X513, X514, and X561) from the five bacterial strains were used to examine physiological characteristics. These thermophilic bacteria were able to use acetate, glucose, hydrogen, lactate, pyruvate, succinate, and xylose as electron donors while reducing Fe(III), cobalt(III), chromium(VI), manganese(IV), and uranium(VI) at 60°C. One of the isolates (X514) was also able to utilize hydrogen as an electron donor for Fe(III) reduction. These bacteria exhibited diverse mineral precipitation capabilities, including the formation of magnetite (Fe 3 O 4 ), siderite (FeCO 3 ), rhodochrosite (MnCO 3 ), and uraninite (UO 2 ). The gas composition of the incubation headspace and the ionic composition of the incubation medium exerted profound influences on the types of minerals formed. The susceptibility of the thermophilic Fe(III)-reducing cultures to metabolic inhibitors specific for ferric reductase, hydrogenase, and electron transport indicated that iron reduction by these bacteria is an enzymatic process.

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Section: Methodsmentioning

confidence: 99%

Isolation and Characterization of Metal-Reducing Thermoanaerobacter Strains from Deep Subsurface Environments of the Piceance Basin, Colorado

Roh

Liu

Huang

et al. 2002

Appl Environ Microbiol

144

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“…Hydrotalcites are important in the removal of environmental hazards in acid mine drainage [9,10]. Hydrotalcite formation also offers a mechanism for the disposal of radioactive wastes [11]. Hydrotalcite formation may also serve as a means of heavy metal removal from heavy metal contaminated waters [12].…”

Section: Introductionmentioning

confidence: 99%

Thermogravimetric analysis of hydrotalcites based on the takovite formula NixZn6-xAl2(OH)16(CO3)·4H2O

Lin

Adebajo

Frost

et al. 2005

J Therm Anal Calorim

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High resolution thermogravimetric analysis (HRTG) coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of zinc-modified hydrotalcites of takovite formulation (Ni x Zn 6-x Al 2 (CO 3 )(OH) 16 .4H 2 O) where x varies from 0 to 6. X-ray diffraction data indicate an increase in the crystallinity and decrease in the interlayer spacing of the materials with increase in the zinc composition. The results of HRTG and mass spectrometry (MS) indicate that water is lost in two major steps at 90-150 and 160-300 °C, with carbon dioxide coming off simultaneously at the second step at 200-300 °C. Further loss of CO 2 was also observed at about 550-560 °C and 735-765 °C due to decomposition of carbonate chemically bound to layer Zn 2+ and Al 3+ cations, respectively. These two steps are attributed to dehydration and dehydroxylation/decarbonation, respectively. The temperature of dehydration was found to increase linearly with increase in the moles of zinc in the takovite formula. In contrast, the temperature of dehydroxylation/decarbonation decreases almost linearly with increase in zinc composition from Ni 5 Zn 1 hydrotalcite. These observations are discussed in terms of the effects of stabilisation of the layer structure, the electronegativity of the layer metals, the charge-to-size ratio of the layer cations and the layer-interlayer hydrogen bonding interactions. Chemical reactions are proposed for the decomposition of the synthesised takovite and zinc-substituted hydrotalcites.

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“…These materials are effective traps for selenium as selenate, and react effectively with chromate, reducing it to Cr(III) as hydroxide or, possibly, as a component of modified LDH (Loyaux-Lawniczak et al, 1999). The observed formation of LDH phases, when metallic Fe is used in the reductive removal of U and Tc, results in the incorporation of these radionuclides into highly insoluble phases (Roh et al, 2000).…”

Section: Chemistry Of Layered Double Hydroxidesmentioning

confidence: 99%

Potential applications of nanostructured materials in nuclear waste management.

Braterman

Phol²,

et al. 2003

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This report summarizes the results obtained from a Laboratory Directed Research & Development (LDRD) project entitled "Investigation of Potential Applications of SelfAssembled Nanostructured Materials in Nuclear Waste Management". The objectives of this project are to (1) provide a mechanistic understanding of the control of nanometerscale structures on the ion sorption capability of materials and (2) develop appropriate engineering approaches to improving material properties based on such an understanding. 4 The project has been focused on two types of nanostructured materials: self-assembled mesoporous materials and layered double hydroxides. The major results are summarized below:• Acid-base titration experiments were performed on both mesoporous alumina and alumina particles under various ionic strengths. Under the same chemical conditions, the surface charge per mass on mesoporous alumina was as much as 45 times higher than that on alumina particles. This difference cannot be fully explained by the surface area difference between the two materials. The titration data have demonstrated that the nano-scale confinement has a significant effect, most likely via the overlap of the electric double layer (EDL), on ion sorption onto mesopore surfaces. This effect cannot be adequately modeled by existing surface complexation models, which were developed mostly for an unconfined solid-water interface.• As the pore size is reduced to a few nanometers, the difference between surface acidity constants (∆pK = pK 2 -pK 1 ) decreases, giving rise to a higher surface charge density on a nanopore surface than that on an unconfined mineral-water interface. The change in surface acidity constants results in a shift of ion sorption edges and enhances ion sorption on nanopore surfaces. Also, the water activity in a nanopore is greatly reduced, thus increasing the tendency for inner sphere complexation and mineral precipitation. All these effects combine to preferentially enrich trace elements in nanopores. This enrichment mechanism has a significant implication to many fundamental geochemical issues such as the irreversibility of ion sorption/desorption and the bioavailability of subsurface contaminants. The discovery of this mechanism provides a scientific basis for engineering high-performance ion adsorbents for nuclear waste management.• Layered double hydroxides (LDH) have shown a great promise for removing anionic contaminants. The anion sorption coefficients (K d ) have been measured for both activated and non-activated Mg-Al LDH materials. The activated material has a much higher anion sorption coefficient than the non-activated one, indicating that calcination can significantly improve anion sorption capacity of LDH. Sorption isotherms for Re and Se on the activated LDH material roughly follow the Freundlich isotherm, indicating the existence of various sorption sites with different sorption capabilities. Anions tend to first sorb on the external surface sites. As the anion concentration or the ionic strength ...

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Incorporation of Radioactive Contaminants into Pyroaurite-Like Phases by Electrochemical Synthesis

Cited by 47 publications

References 19 publications

Isolation and Characterization of Metal-Reducing Thermoanaerobacter Strains from Deep Subsurface Environments of the Piceance Basin, Colorado

Isolation and Characterization of Metal-Reducing Thermoanaerobacter Strains from Deep Subsurface Environments of the Piceance Basin, Colorado

Thermogravimetric analysis of hydrotalcites based on the takovite formula NixZn6-xAl2(OH)16(CO3)·4H2O

Potential applications of nanostructured materials in nuclear waste management.

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