Speciation Analysis of Aqueous Polyselenide Solutions

Licht, Stuart; Forouzan, Fardad

doi:10.1149/1.2048610

Cited by 47 publications

(76 citation statements)

References 4 publications

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“…This peak was assigned to HSe À . 4,5,10) At pH between 9 and 13, the sample solutions were reddish and showed absorption bands at 220, 282, and 377 nm. These results are indicative of the formation of Se 4 2À .…”

Section: Resultsmentioning

confidence: 99%

“…These results are indicative of the formation of Se 4 2À . 4,5) The UV-Vis spectra of the 1.0 mol dm À3 NaCl sample solutions at pH 7 and pH 10 are shown in Fig. 4 as representative examples.…”

Section: Resultsmentioning

confidence: 99%

“…1). Since the chemical conditions under deep underground environments are likely to be anoxic and reducing, a Se(-II) species of HSe À is considered to be dominant in neutral groundwater, 3) and polyselenide species of Se n 2À (n ¼ 1{4) is considered to be dominant in alkaline groundwater [3][4][5] induced by cementitious materials in radioactive waste repositories (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

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Solubility of Selenium at High Ionic Strength under Anoxic Conditions

Iida

Yamaguchi

Tanaka

et al. 2010

Journal of Nuclear Science and Technology

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Solubility experiments for selenium were performed at high ionic strengths (1.0 and 2.0 mol dm À3 NaCl) under anoxic conditions (p O2 < 10 À6 atm) from undersaturation and oversaturation directions. Equilibrium was attained in 40 days. The dominant aqueous selenium species were identified as hydrogen selenide, HSe À , at pH between 5 and 8, and polyselenide, Se 4 2À , at pH between 9 and 13 by UV-Vis absorption spectrometry. A solubility-limiting solid was determined to be amorphous selenium at pH between 5 and 8, and crystalline selenium at pH between 9 and 13. The equilibrium constants oflog K 0 ¼ À16:67 AE 0:03 ð9 < pH < 13Þand ion interaction coefficients for HSe À and Se 4 2À versus Na þ , "(HSe À , Na þ ) = À0:01 AE 0:10 and "(Se 4 2À , Na þ ) = À0:03 AE 0:02, were determined with the specific ion interaction theory. The standard molar free energies of formation of amorphous selenium and polyselenide species were determined to be Á f G m 0 (Se(am)) = 6:0 AE 2:2 kJ mol À1 , Á f G m 0 (Se 2 2À ) = 111:64 AE 1:61 kJ mol À1 , Á f G m 0 (Se 3 2À ) = 98:68 AE 1:02 kJ mol À1 , and Á f G m 0 (Se 4 2À ) = 95:14 AE 0:17 kJ mol À1 .

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solubility of Selenium at High Ionic Strength under Anoxic Conditions

Iida

Yamaguchi

Tanaka

et al. 2010

Journal of Nuclear Science and Technology

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“…Under low redox and low pH conditions, sulfur is precipitated while selenium is replaced by selenite and selenide, and at high pH, the reverse is true. The formation of soluble polysulfides and polyselenides appears to be a possibility under such circumstances (18,34). At moderate pH values and under reducing conditions, both elements are well within their stability fields and a mixture of the two is precipitated.…”

Section: Discussionmentioning

confidence: 99%

Linked Redox Precipitation of Sulfur and Seleniumunder Anaerobic Conditions by Sulfate-Reducing BacterialBiofilms

Hockin

Gadd

2003

Appl Environ Microbiol

142

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A biofilm-forming strain of sulfate-reducing bacteria (SRB), isolated from a naturally occurring mixed biofilm and identified by 16S rDNA analysis as a strain of Desulfomicrobium norvegicum, rapidly removed 200 M selenite from solution during growth on lactate and sulfate. Elemental selenium and elemental sulfur were precipitated outside SRB cells. Precipitation occurred by an abiotic reaction with bacterially generated sulfide. This appears to be a generalized ability among SRB, arising from dissimilatory sulfide biogenesis, and can take place under low redox conditions and in the dark. The reaction represents a new means for the deposition of elemental sulfur by SRB under such conditions. A combination of transmission electron microscopy, environmental scanning electron microscopy, and cryostage field emission scanning electron microscopy were used to reveal the hydrated nature of SRB biofilms and to investigate the location of deposited sulfur-selenium in relation to biofilm elements. When pregrown SRB biofilms were exposed to a selenite-containing medium, nanometer-sized selenium-sulfur granules were precipitated within the biofilm matrix. Selenite was therefore shown to pass through the biofilm matrix before reacting with bacterially generated sulfide. This constitutes an efficient method for the removal of toxic concentrations of selenite from solution. Implications for environmental cycling and the fate of sulfur and selenium are discussed, and a general model for the potential action of SRB in selenium transformations is presented.Sulfate-reducing bacteria (SRB) are a phylogenetically and physiologically diverse group of bacteria, characterized by their common capacity to conserve energy for growth by linking the oxidation of various substrates to the dissimilatory reduction of sulfate (S 6ϩ ) to sulfide (S 2Ϫ ). As such, SRB comprise a functional group within a sulfuretum, linking broad-scale cycling between sulfate and sulfide by ecological communities of SRB and sulfide-oxidizing bacteria (12, 28). Biological reoxidation of reduced sulfur species typically occurs at oxic-anoxic transition zones and is attributed largely to phototrophs and chemolithotrophs. Small-scale cycling through elemental sulfur (S 0 ) also occurs and is generally attributed to syntrophic associations of sulfide oxidizers and sulfur reducers (3,17).The biological cycling of selenium is receiving increasing attention, due not only to the biological importance of selenium as an essential trace element but also to the potential for selenium pollution to cause significant ecological damage (42). Selenium is a group 16 metalloid element possessing several stable oxidation states. Under oxic conditions, selenium is present mostly as the oxyanions selenite (SeO 3 2Ϫ , Se 4ϩ oxidation state) and selenate (SeO 4 2Ϫ , Se 6ϩ oxidation state), whereas under anoxic conditions, selenide (Se 2Ϫ ) and elemental selenium (Se 0 ) appear predominant (5, 6). Selenium is incorporated by organisms through selenide, is important in some enzyme systems,...

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“…1. These peaks were assigned to HSe À and Se 4 2À , respectively, 5,6) showing that Se was dissolved as stable species under the reducing condition. 4) Experimental data from the sorption experiments using rocks and minerals are summarized in Tables 5 and 6, respectively.…”

Section: Selenium Speciesmentioning

confidence: 99%

Sorption Behavior of Selenium(−II) on Rocks under Reducing Conditions

Iida

Tanaka

Yamaguchi

et al. 2011

J. Nucl. Sci. Technol.

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The sorption of radionuclides on rocks is an important factor for performance assessment of geologic disposal of radioactive wastes. Batch sorption experiments under reducing conditions were carried out to investigate the sorption behavior of selenium onto granodiorite, sandy mudstone, tuffaceous sandstone, and their major constituent minerals and accessory minerals. Rock cores and groundwater employed in the experiments were sampled with special care to avoid exposing the cores and groundwater to air to minimize their oxidation. Selenium was spiked as HSe À and Se 4 2À in the experimental solutions, and reducing conditions were maintained throughout the sorption periods. Distribution coefficients, K d (m 3 kg À1 ), were obtained in the ranges of 2:2 Â 10 À4 to 4:0 Â 10 À3 m 3 kg À1 for granodiorite, 3:3 Â 10 À2 to 5:6 Â 10 À2 m 3 kg À1 for sandy mudstone, and 2:9 Â 10 À2 to 8:2 Â 10 À2 m 3 kg À1 for tuffaceous sandstone at pHs 8.5 to 11.5. The dominant sorbent minerals for selenium over a neutral to alkaline pH range were determined to be biotite for the granodiorite samples and pyrite for the sandy mudstone and tuffaceous sandstone samples.

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Speciation Analysis of Aqueous Polyselenide Solutions

Cited by 47 publications

References 4 publications

Solubility of Selenium at High Ionic Strength under Anoxic Conditions

Solubility of Selenium at High Ionic Strength under Anoxic Conditions

Linked Redox Precipitation of Sulfur and Seleniumunder Anaerobic Conditions by Sulfate-Reducing BacterialBiofilms

Sorption Behavior of Selenium(−II) on Rocks under Reducing Conditions

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