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Jeanet Conradie - One of the best experts on this subject based on the ideXlab platform.

  • Structures of solvated Ferrous Ion clusters in ammonia and spin-crossover at various temperatures
    New Journal of Chemistry, 2019
    Co-Authors: Ousman Boukar, Jean Jules Fifen, Alhadji Malloum, Zoubeida Dhaouadi, Hassen Ghalila, Jeanet Conradie
    Abstract:

    Iron plays a key role in the evolutIon of living systems and so it is an essential element in a wide range of biological phenomena, energy transductIon mechanisms, and oxygen carriers. In this work, we investigated various isomers of the Fe2+(NH3)n=1–10 complex in the singlet, triplet and quintet spin states in the gas phase and their relative stabilities in a wide range of temperatures (0 K and 25–400 K). All the calculatIons are performed at the M06-2X/6-31++G(d,p) and MP2/6-31++G(d,p) levels of theory. It emerges from this work that although M06-2X could not in all cases be suitable for investigating the structural parameters of this complex in the singlet spin state, it gives excellent relative energies as compared to MP2 results and therefore could be recommended for evaluating the solvatIon free energy of the Ferrous Ion rather than the time consuming MP2 method. In additIon, with a few exceptIons, structures obtained at the MP2 and M06-2X levels of theory are very similar. The solvated Ferrous Ion in the singlet, triplet and quintet spin states in ammonia is hexa-coordinated, irrespective of the temperature. This result slightly contrasts the reported finding concerning the hydrated Ferrous Ion for which the CN is ∼6 around 215 K and less at a higher temperature of 305 K. Furthermore, the quintet spin state structures dominate exclusively lower spin state ones at all temperatures in such a way that no natural spin-crossover is possible between the quintet spin state and the lower spin states in the clusters of Fe2+(NH3)n=1–10. However, the spin-crossover is naturally possible around 200 K between the singlet and the triplet spin states for n ≥ 6, and the latter is preferred at high temperatures while the former is preferred at lower temperatures. We also pointed out that the available clustering energies at modest or higher cluster sizes (n > 7) for solvated metal Ions neither depend on the spin state of the metal, or on the type of metal (alkaline earth, transitIon metals,…), or on the ligand type (ammonia, water,…). Thus, the solvatIon energies of metal Ions did not depend on their spin states. We also anticipated that the solvatIon free energy or enthalpy of the Ferrous Ion in ammonia could be determined by clustering up to n = 9 or 10.

Kenneth L. Sperry - One of the best experts on this subject based on the ideXlab platform.

  • Persulfate oxidatIon for in situ remediatIon of TCE. II. Activated by chelated Ferrous Ion.
    Chemosphere, 2004
    Co-Authors: Chenju Liang, Clifford J. Bruell, Michael C. Marley, Kenneth L. Sperry
    Abstract:

    In situ chemical oxidatIon (ISCO) is a technique used to remediate contaminated soil and groundwater systems. It has been postulated that sodium persulfate (Na2S2O8) can be activated by transitIon metal Ions such as Ferrous Ion (Fe2+) to produce a powerful oxidant known as the sulfate free radical (SO4-*) with a redox potential of 2.6 V, which can potentially destroy organic contaminants. In this laboratory study persulfate oxidatIon of dissolved trichloroethylene (TCE) was investigated in aqueous and soil slurry systems under a variety of experimental conditIons. A chelating agent (i.e., citric acid) was used in attempt to manipulate the quantity of Ferrous Ion in solutIon by providing an appropriate chelate/Fe2+ molar ratio. In an aqueous system a chelate/Fe2+ molar ratio of 1/5 (e.g., S2O8(2)-/chelate/Fe2+/TCE ratio of 20/2/10/1) was found to be the lowest acceptable ratio to maintain sufficient quantities of Fe2+ activator in solutIon resulting in nearly complete TCE destructIon after only 20 min. The availability of Fe2+ appeared to be controlled by adjusting the molar ratio of chelate/Fe2+. In general, high levels of chelated Ferrous Ion concentratIons resulted in faster TCE degradatIon and more persulfate decompositIon. However, if initial Ferrous Ion contents are relatively low, sufficient quantities of chelate must be provided to ensure the chelatIon of a greater percentage of the limited Ferrous Ion present. Citric acid chelated Ferrous Ion appeared effective for TCE degradatIon within soil slurries but required longer reactIon times. AdditIonally, the use of citric acid without the additIon of supplemental Fe2+ in soil slurries, where the citric acid apparently extracted native metals from the soil, appeared to be somewhat effective at enhancing persulfate oxidatIon of TCE over extended reactIon times. A comparison of different chelating agents revealed that citric acid was the most effective.

  • Persulfate oxidatIon for in situ remediatIon of TCE. I. Activated by Ferrous Ion with and without a persulfate-thiosulfate redox couple.
    Chemosphere, 2004
    Co-Authors: Chenju Liang, Clifford J. Bruell, Michael C. Marley, Kenneth L. Sperry
    Abstract:

    Abstract The objective of the laboratory study is to examine the conditIons under which transitIon metal Ions (e.g., Ferrous Ion, Fe 2+ ) could activate the persulfate anIon (S 2 O 8 2− ) to produce a powerful oxidant known as the sulfate free radical (SO 4 − ) with a standard redox potential of 2.6 V. The SO 4 − is capable of destroying groundwater contaminants in situ such as trichloroethylene (TCE). Experiments using Fe 2+ as an activator under various molar ratios of S 2 O 8 2− /Fe 2+ /TCE in an aqueous system indicated that partial TCE degradatIon occurred almost instantaneously and then the reactIon stalled. Either destructIon of SO 4 − in the presence of excess Fe 2+ or the rapid conversIon of all Fe 2+ to Fe 3+ limited the ultimate oxidizing capability of the system. Sequential additIon of Fe 2+ in small increments resulted in an increased TCE removal efficiency. Therefore, it appeared that Fe 2+ played an important role in generating SO 4 − . An observatIon of oxidatIon–reductIon potential (ORP) variatIons revealed that the additIon of sodium thiosulfate (Na 2 S 2 O 3 ) to the Ferrous Ion activated persulfate system could significantly decrease the strong oxidizing conditIons. It was hypothesized that the thiosulfate induced reducing conditIons might convert Fe 3+ to a lower valence state of Fe 2+ , making the Fe 2+ available to activate persulfate decompositIon. The sequential additIon of thiosulfate (S 2 O 3 2− ), after the initial stalling of Ferrous Ion activated persulfate oxidatIon of TCE, resulted in an improvement in TCE removal. The Ferrous Ion activated persulfate–thiosulfate redox couple resulted in fairly complete TCE degradatIon in aqueous systems in a short time frame. In soil slurry systems, TCE degradatIon was slower in comparison to aqueous systems.

Helen R. Watling - One of the best experts on this subject based on the ideXlab platform.

  • A comparative study of substrate utilisatIon by Sulfobacillus species in mixed Ferrous Ion and tetrathIonate growth medium
    Hydrometallurgy, 2010
    Co-Authors: D.w. Shiers, D.e. Ralph, Helen R. Watling
    Abstract:

    Concurrent Ferrous Ion and tetrathIonate utilisatIon by Sulfobacillus acidophilus, Sb. thermosulfidooxidans, Sb. thermotolerans, and Sb. sibiricus grown separately in batch culture in dual-substrate media containing Ferrous Ion and tetrathIonate was investigated. For all species, tetrathIonate-adapted cells oxidised both substrates concurrently, achieving at least 20% oxidatIon of the second substrate before the first substrate was exhausted. Sequential substrate utilisatIon was observed for iron(II)-adapted cells for three of the four species and all iron(II)-adapted cell lines commenced oxidatIon of Ferrous Ions ahead of tetrathIonate. AdaptatIon to iron(II) or tetrathIonate of the test species had little impact on subsequent Ferrous Ion oxidatIon. However, tetrathIonate oxidatIon was affected by growth history. Compared with their respective tetrathIonate-adapted cell lines, cells adapted to iron(II) exhibited either significantly longer lag times and/or longer periods to complete tetrathIonate oxidatIon once it had commenced. PolythIonate intermediates measured during tetrathIonate oxidatIon to sulfate included thiosulfate, pentathIonate and hexathIonate for the four species. The intermediate trithIonate was only detected in Sb. thermotolerans cultures.

  • Substrate utilisatIon by Sulfobacillus thermosulfidooxidans in mixed Ferrous Ion and tetrathIonate growth medium
    Advanced Materials Research, 2009
    Co-Authors: D.w. Shiers, D.e. Ralph, Helen R. Watling
    Abstract:

    Sulfobacillus thermosulfidooxidans cultures adapted to Ferrous or tetrathIonate Ions were inoculated into media containing both substrates. In batch culture, cells showed a preference for oxidising Ferrous Ion followed by tetrathIonate. TetrathIonate oxidatIon was slower in Ferrous-adapted cells. Biomass formatIon exhibited an exponential growth phase during Ferrous Ion oxidatIon followed by an exponential growth phase during tetrathIonate oxidatIon. Sequential utilisatIon of Ferrous Ion followed by tetrathIonate Ion was observed when equimolar amounts of substrates or electron-equivalent amounts were provided.

Jaffar Nouroozzadeh - One of the best experts on this subject based on the ideXlab platform.

  • Ferrous Ion oxidatIon in presence of xylenol orange for detectIon of lipid hydroperoxides in plasma
    Methods in Enzymology, 1999
    Co-Authors: Jaffar Nouroozzadeh
    Abstract:

    Publisher Summary This chapter discusses Ferrous Ion oxidatIon in presence of xylenol orange for detectIon of lipid hydroperoxides (ROOHs) in plasma. The Ferrous oxidatIon in xylenol orange 2 (FOX2) assay in conjugatIon with triphenylphosphine (TPP) has been implemented for the measurement of plasma ROOHs. TPP reduces ROOHs to their corresponding alcohols while itself being converted to triphenylphosphine oxide. This maneuver was also necessary to generate a proper control, since plasma contains interfering components, mainly ferric Ions that are detected by xylenol orange. There are other advantages of the FOX2 assay over existing techniques: (a) the kinetics of the reactIon are independent of the chemical structure of ROOHs, (b) no extractIon step is normally needed for analysis of liposomes and lipoprotein suspensIons because of the use of 90% methanol/25 mM H 2 SO 4 that denatures proteins sufficiently for access of the Ferrous Ions to available ROOHs.

Kf Chen - One of the best experts on this subject based on the ideXlab platform.

  • Methyl Tert-Butyl Ether (MTBE) DegradatIon by Ferrous Ion-Activated Persulfate OxidatIon: Feasibility and Kinetics Studies 
    'Water Environment Federation', 2020
    Co-Authors: Kf Chen
    Abstract:

    [[abstract]]The objective of this study was to evaluate the feasibility of using Ferrous Ion-activated persulfate oxidatIon to remediate groundwater contaminated with methyl tert-butyl ether (MTBE). In this study, batch experiments were conducted to evaluate the effects of various factors on the efficiency of MTBE degradatIon including persulfate concentratIons, Ferrous Ion concentratIons, and persulfate coupled with hydrogen peroxide. Results show that Ferrous Ion-activated persulfate oxidatIon was capable of degrading MTBE efficiently. Persulfate and Ferrous Ion concentratIons correlated with MTBE degradatIon rates. However, excess additIon of Ferrous Ion resulted in decreased MTBE degrading rates most likely because of competitIon for sulfate free radicals between Ferrous Ion and MTBE. Two main byproducts of MTBE degradatIon, tert-butyl formate and tert-butyl alcohol, were detected in the experiments; both were, however, subsequently degraded. Results of sulfate analysis show that proper additIon of Ferrous Ion could prevent unnecessary persulfate decompositIon. Water Environ. Res., 81, 687 (2009).[[note]]SC

  • ApplicatIon of persulfate to remediate petroleum hydrocarbon-contaminated soil: Feasibility and comparison with common oxidants 
    ELSEVIER SCIENCE BV, 2020
    Co-Authors: Kf Chen
    Abstract:

    [[abstract]]In this study, batch experiments were conducted to evaluate the feasibility of petroleum-hydrocarbon contaminated soil remediatIon using persulfate oxidatIon. Various controlling factors including different persulfate and Ferrous Ion concentratIons, different oxidants (persulfate, hydrogen peroxide, and permanganate), and different contaminants (diesel and fuel oil) were considered. Results show that persulfate oxidatIon is capable of treating diesel and fuel oil contaminated soil. Higher persulfate and Ferrous Ion concentratIons resulted in higher diesel degrading rates within the applied persulfate/Ferrous Ion molar ratios. A two-stage diesel degradatIon was observed in the batch experiments. In additIon, treatment of diesel-contaminated soil using in situ metal mineral activatIon under ambient temperature (e.g., 25 degrees C) may be a feasible optIon for site remediatIon. Results also reveal that persulfate anIons could persist in the system for more than five months. Thus, sequential injectIons of Ferrous Ion to generate sulfate free radicals might be a feasible way to enhance contaminant oxidatIon. Diesel oxidatIon efficiency and rates by the three oxidants followed the sequence of hydrogen peroxide > permanganate > persulfate in the limited timeframes. Results of this study indicate that the applicatIon of persulfate oxidatIon is a feasible method to treat soil contaminated by diesel and fuel oil. (C) 2011 Elsevier B.V. All rights reserved.[[note]]SC

  • Methyl tert-butyl ether (MTBE) degradatIon by Ferrous Ion-activated persulfate oxidatIon: feasibility and kinetics studies.
    Water environment research : a research publication of the Water Environment Federation, 2009
    Co-Authors: Kf Chen, C. M. Kao, Rao Y. Surampalli, S. H. Liang
    Abstract:

    The objective of this study was to evaluate the feasibility of using Ferrous Ion-activated persulfate oxidatIon to remediate groundwater contaminated with methyl tert-butyl ether (MTBE). In this study, batch experiments were conducted to evaluate the effects of various factors on the efficiency of MTBE degradatIon including persulfate concentratIons, Ferrous Ion concentratIons, and persulfate coupled with hydrogen peroxide. Results show that Ferrous Ion-activated persulfate oxidatIon was capable of degrading MTBE efficiently. Persulfate and Ferrous Ion concentratIons correlated with MTBE degradatIon rates. However, excess additIon of Ferrous Ion resulted in decreased MTBE degrading rates most likely because of competitIon for sulfate free radicals between Ferrous Ion and MTBE. Two main byproducts of MTBE degradatIon, tert-butyl formate and tert-butyl alcohol, were detected in the experiments; both were, however, subsequently degraded. Results of sulfate analysis show that proper additIon of Ferrous Ion could prevent unnecessary persulfate decompositIon.