- Catalytic activity of CuS nanoparticles in hydrosulfide ions air oxidation
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The most efficient technique for H2S removal from the wastewaters is the catalytic aeration of the wastewaters, i.e., H2S oxidation in air-saturated solutions in the presence of catalysts. Photophysical characteristics of colloidal CuS nanoparticles synthesized in various conditions and stabilized in aqueous solutions with sodium polyphosphate were studied. Hydrosulfide ions air oxidation in aqueous solutions at room temperatures and 1 atm proceeded with small rates in the absence of catalysis and increased, substantially upon the injection of CuS nanoparticles into a reacting mixture. The rate of HS- catalytic oxidation grew at an increase in molar CuS concentration, initial concentration of Na2S, volume fraction of oxygen in gas mixture bubbled into the reactor, and pH of a solution (≤ 11.9). A scheme for the mechanism of HS- catalytic oxidation was proposed. According to the scheme, HS- oxidation is a chain radical reaction initiated on the surface of CuS nanoparticles and propagated further in the bulk of a solution.
- Raevskaya,Stroyuk,Kuchmii,Kryukov
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- Oxidation of biologically relevant chalcogenones and their Cu(I) complexes: Insight into selenium and sulfur antioxidant activity
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Hydroxyl radical damage to DNA causes disease, and sulfur and selenium antioxidant coordination to hydroxyl-radical-generating Cu+ is one mechanism for their observed DNA damage prevention. To determine how copper binding results in antioxidant
- Kimani, Martin M.,Bayse, Craig A.,Stadelman, Bradley S.,Brumaghim, Julia L.
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- DNA damage induced by sulfite autoxidation catalyzed by copper(II) tetraglycine complexes
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Copper(II)/(III) tetraglycine complexes were investigated for their ability to catalyze the autoxidation of sulfite resulting in oxidative DNA damage. The focus of this work is on DNA damage by Cu(III) and oxysulfur radicals formed by the oxidation of S(IV) oxides by dissolved oxygen in the presence of Cu(II) tetraglycine complexes. The results suggest that sulfite is rapidly oxidized by oxygen in the presence of Cu(II) complexes producing Cu(III) tetraglycine, which can be monitored spectrophotometrically at 365 nm. A synergistic effect of Cu(II) with a second metal ion (Ni(II), Co(II) or Mn(II) traces) was observed. The Royal Society of Chemistry 2005.
- Moreno, Ruben G. M.,Alipazaga, Maria V.,Medeiros, Marisa H. G.,Coichev, Nina
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- General Model for the Nonlinear pH Dynamics in the Oxidation of Sulfur(-II) Species
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A general kinetic feature has been observed experimentally for the oxidation of the sulfur(-II) species thiosulfate, thiourea, thiocyanate, and sulfide by chlorite and other multi-equivalent oxidants under appropriate, unbuffered batch conditions. This fingerprint consists of an initial rise in pH followed by an autocatalytic drop in pH or oligo-oscillatory behavior. These systems also exhibit oscillations and other complex dynamical behavior in a continuous-flow stirred tank reactor (CSTR). The previously proposed general models that are oxidant based do not successfully explain the observed pH effects. We propose a simple, general model that is based upon the changing oxidation states of sulfur to explain the general pH features. The scheme qualitatively models autocatalysis and oligo-oscillations in batch and simple and complex oscillations in a CSTR. The general model consists of three separate stages: negative hydrogen ion feedback (S(-II) to S(0)), a transition of S(0) to S(IV), and positive proton feedback from S(IV) to S(VI).
- Rushing, C. Wayland,Thompson, Richard C.,Gao, Qingyu
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- The preparation and properties of N-fluoroformyliminosulfur difluoride, SF2=NCOF
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The inorganic isocyanates derived from silicon, phosphorus, and sulfur have been found to react readily with sulfur tetrafluoride to give, in common, the novel compound, N-fluoroformyliminosulfur difluoride, SF2=NCOF, the preparation and proper
- Clifford, Alan F.,Kobayashi, Calvin S.
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- Evidence for Multistep Reactions in the Iron(III) Catalysed Autoxidation of Sulphur(IV) Oxides: Possible Steps during Acid Rain Formation
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Kinetic and spectroscopic evidence is presented for the formation and decomposition of iron(III)-sulphur(IV) transients during the iron(III) catalysed autoxidation of sulphur(IV) oxides in aqueous solution, for which four different reaction steps could be
- Kraft, Jochen,Eldik, Rudi van
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- Kinetics and Mechanism of the Ferrate Oxidation of Thiosulfate and Other Sulfur-Containing Species
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The kinetics of the reaction of ferrate, FeO42-, with several sulfur-containing species in aqueous media have been investigated, and the results are reported. It was found that, when the reductant is in excess, ferrate rapidly oxidizes thiosulfate to sulfite, benzenesulfinate to benzenesulfonate, methionine to its corresponding sulfoxide, and dimethyl sulfoxide to dimethyl sulfone. The rate law for each reaction is first order with respect to each reactant and first order with respect to the hydrogen ion concentration. A mechanism for each oxidation reaction is discussed.
- Johnson, Michael D.,Read, John F.
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- Oxidation of thiocyanate with H2O2 catalyzed by [RuIII(edta)(H2O)]-
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The [RuIII(edta)(H2O)]- (edta4- = ethylenediaminetetraacetate) complex is shown to catalyze the oxidation of thiocyanate (SCN-) with H2O2 mimicking the action of peroxidases. The kinetics of the catalytic oxidation process was studied by using stopped-flow and rapid scan spectrophotometry as a function of [RuIII(edta)], [H2O2], [SCN-], pH (3.2-9.1) and temperature (15-30 °C). Spectral analyses and kinetic data are suggestive of a catalytic pathway in which hydrogen peroxide reacts directly with thiocyanate coordinated to the RuIII(edta) complex. Catalytic intermediates such as [RuIII(edta)(OOH)]2- and [Ru V(edta)(O)]- were found to be non-reactive in the oxidation process under the specified conditions. Formation of SO 42- and OCN- was identified as oxidation products in ESI-MS experiments. A detailed mechanism in agreement with the spectral and kinetic data is presented. The Royal Society of Chemistry 2013.
- Chatterjee, Debabrata,Paul, Barnali,Mukherjee, Rupa
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- The kinetics and mechanism of the oxidation of inorganic oxysulfur compounds by potassium ferrate: Part I. Sulfite, thiosulfate and dithionite ions
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The kinetics and mechanism of the oxidation of the sulfite (SO32-), thiosulfate (S2O32-) and dithionite (S2O42-) ions by ferrate (FeO42-) ions was studied under pseudo-first-order conditions and, in addition, the reaction with thiosulfate ions was studied under non-pseudo-first-order conditions. Previous work on sulfite and thiosulfate was repeated and extended, specifically over a larger pH range, and using non-pseudo-first-order kinetics. Dithionite was only studied at high pH values because of rapid hydrolysis below a pH of about 10. The kinetics for sulfite and thiosulfate showed a first-order dependence on hydrogen, oxysulfur and ferrate ion concentrations at high pH values, but became independent of the hydrogen ion concentration below a pH of about 8.5. The kinetics for dithionite involved two terms, one being first-order in the hydrogen, dithionite and ferrate ion concentrations, and the other being first-order in only the dithionite and ferrate ions. For all three reductants the proposed mechanism has a rate-determining step involving reaction between the protonated ferrate and the oxysulfur ions. For dithionite there is also a rate-determining step involving reaction between unprotonated ferrate and dithionite. All the oxysulfur ions gave Fe(III) as a product. Sulfite produced sulfate, whereas thiosulfate and dithionite gave sulfite.
- Read, John F,John, Jennifer,MacPherson, Jan,Schaubel, Catherine,Theriault, Annie
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- Some perfluoroalkyliminosulfur derivatives
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Trifluoromethyliminosulfur dichloride and pentafluoroethyliminosulfur dichloride are prepared by reaction of aluminum trichloride with trifluoromethyliminosulfur difluoride and pentafluoroethyliminosulfur difluoride, respectively. These imino dichlorides
- Lustig, Max
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- Photocatalytic Oxidation of Sulfur on the Doped TiO2 Catalysts
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TiO2 (anatase) doped with various elements was used as the photocatalyst in the production of sulfuric acid from sulfur in water into which O2 was bubbled.The catalysts doped with typical elements having one and two valencies showed high catalytic activit
- Matsumoto, Yasumichi,Yamaguchi, Yasuhide,Sato, Ei-ichi
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- 177. Photoreduction of Thiosulfate in Semiconductor Dispersions
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Conduction band electrons produced by band gap excitation of TiO2-particles reduce efficiently thiosulfate to sulfide and sulfite. This reaction is confirmed by electrochemical investigations with polycrystalline TiO2-electrodes.The valence ban
- Borgarello, Enrico,Desilvestro, Jean,Graetzel, Michael,Pelizzetti, Ezio
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- Kinetics and mechanism of the decomposition of tetrathionate ion in alkaline medium
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The kinetics of the alkaline decomposition of tetrathionate has been studied spectrophotometrically in the pH range of 9.2-12.2 using both phosphate/hydrogen phosphate and carbonate/hydrogen carbonate as buffer systems and by adjusting the ionic strength to I = 0.5 M with sodium perchlorate at T = 25.0 ± 0.1°C. Matrix rank analysis of the spectra recorded between 265 and 330 nm shows the presence of three independent absorbing species. Besides tetrathionate, thiosulfate and trithionate are identified as absorbing products of the decomposition, but sulfite and a trace amount of sulfate are also formed during the alkaline degradation process. With pentathionate, sulfoxylic acid (S(OH)2), S2O3OH-, and S3O3OH- as key intermediates, a 10-step kinetic model is proposed with six fitted kinetic parameters to take all the important characteristics of the experimental curves into account. On the basis of the stoichiometric measurements and the model proposed, it is also enlightened that the product distribution of the reaction continuously varies with pH; thus the kinetic traces cannot be evaluated by assuming a single stoichiometry in contrast to recent studies. Buffer dependence of the decomposition is also discussed.
- Varga, Denes,Horvath, Attila K.
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- Light-Activated generation of nitric oxide (NO) and sulfite anion radicals (SO3-) from a ruthenium(ii) nitrosylsulphito complex
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This manuscript describes the preparation of a new Ru(ii) nitrosylsulphito complex, trans-[Ru(NH3)4(isn)(N(O)SO3)]+ (complex 1), its spectroscopic and structural characterization, photochemistry, and thermal reactivity. Complex 1 was obtained by the reaction of sulfite ions (SO32-) with the nitrosyl complex trans-[Ru(NH3)4(isn)(NO)]3+ (complex 2) in aqueous solution resulting in the formation of the N-bonded nitrosylsulphito (N(O)SO3) ligand. To the best of our knowledge, only four nitrosylsulphito metal complexes have been described so far (J. Chem. Soc., Dalton Trans., 1983, 2465-2472), and there is no information about the photochemistry of such complexes. Complex 1 was characterized by spectroscopic means (UV-Vis, EPR, FT-IR, 1H-and 15N-NMR), elemental analysis and single-crystal X-ray diffraction. The X-ray structure of the precursor complex 2 is also discussed in the manuscript and is used as a reference for comparisons with the structure of 1. Complex 1 is water-soluble and kinetically stable at pH 7.4, with a first-order rate constant of 3.1 × 10-5 s-1 for isn labilization at 298 K (t1/2 ~ 373 min). Under acidic conditions (1.0 M trifluoroacetic acid), 1 is stoichiometrically converted into the precursor complex 2. The reaction of hydroxide ions (OH-) with 1 and with 2 yields the Ru(ii) nitro complex trans-[Ru(NH3)4(isn)(NO2)]+ with second-order rate constants of 2.1 and 10.5 M-1 s-1 (at 288 K), respectively, showing the nucleophilic attack of OH- at the nitrosyl in 2 (Ru-NO) and at the nitrosylsulphito in 1 (Ru-N(O)SO3). The pKa value of the-SO3 moiety of the N(O)SO3 ligand in 1 was determined to be 5.08 ± 0.06 (at 298 K). The unprecedented photochemistry of a nitrosylsulphito complex is investigated in detail with 1. The proposed mechanism is based on experimental (UV-Vis, EPR, NMR and Transient Absorption Laser Flash Photolysis) and theoretical data (DFT) and involves photorelease of the N(O)SO3- ligand followed by formation of nitric oxide (NO) and sulfite radicals (SO3-, sulfur trioxide anion radical).
- Roveda, Antonio C.,Santos, Willy G.,Souza, Maykon L.,Adelson, Charles N.,Gon?alves, Felipe S.,Castellano, Eduardo E.,Garino, Claudio,Franco, Douglas W.,Cardoso, Daniel R.
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supporting information
p. 10812 - 10823
(2019/07/31)
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- Kinetics and mechanism of the inner-sphere reduction of hexachloroplatinate(IV) by dithionite in acetate buffer
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The kinetics of reduction of hexachloroplatinate( IV) by dithionite have been examined spectrophotometrically in sodium acetate-acetic acid buffer medium in the temperature range 288-303 K. The reaction is first order in both platinum(IV) species and dith
- Pal, Biswajit,Gupta, Kalyan K. Sen
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p. 671 - 678
(2013/01/15)
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- Mechanism of decomposition of the human defense factor hypothiocyanite near physiological pH
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Relatively little is known about the reaction chemistry of the human defense factor hypothiocyanite (OSCN-) and its conjugate acid hypothiocyanous acid (HOSCN), in part because of their instability in aqueous solutions. Herein we report that HOSCN/OSCN- can engage in a cascade of pH- and concentration-dependent comproportionation, disproportionation, and hydrolysis reactions that control its stability in water. On the basis of reaction kinetic, spectroscopic, and chromatographic methods, a detailed mechanism is proposed for the decomposition of HOSCN/OSCN- in the range of pH 4-7 to eventually give simple inorganic anions including CN -, OCN-, SCN-, SO32-, and SO42-. Thiocyanogen ((SCN)2) is proposed to be a key intermediate in the hydrolysis; and the facile reaction of (SCN) 2 with OSCN- to give NCS(=O)SCN, a previously unknown reactive sulfur species, has been independently investigated. The mechanism of the aqueous decomposition of (SCN)2 around pH 4 is also reported. The resulting mechanistic models for the decomposition of HOSCN and (SCN) 2 address previous empirical observations, including the facts that the presence of SCN- and/or (SCN)2 decreases the stability of HOSCN/OSCN-, that radioisotopic labeling provided evidence that under physiological conditions decomposing OSCN- is not in equilibrium with (SCN)2 and SCN-, and that the hydrolysis of (SCN)2 near neutral pH does not produce OSCN-. Accordingly, we demonstrate that, during the human peroxidase-catalyzed oxidation of SCN-, (SCN)2 cannot be the precursor of the OSCN- that is produced.
- Kalmar, Jozsef,Woldegiorgis, Kelemu L.,Biri, Bernadett,Ashby, Michael T.
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p. 19911 - 19921
(2012/01/31)
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- Novel non-aqueous Fe(III)/Fe(II) redox couple for the catalytic oxidation of hydrogen sulfide to sulfur by air
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A series of Fe(iii) salts and organic solvents have been screened to develop novel non-aqueous catalysts for the conversion of H2S to sulfur. FeCl3/95% N-methylpyrrolidinone/5% H2O was found to be a most efficient non-aqueous system. The process chemistry, the proposed mechanism of catalytic oxidation of H2S, and the electrochemistry are discussed. The Royal Society of Chemistry 2006.
- Hua, Guoxiong,Zhang, Qingzhi,McManus, Derek,Slawin, Alexandra M. Z.,Woollins, J. Derek
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p. 1147 - 1156
(2007/10/03)
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- Thermal and photochemical reactions of bis(diamine)(sulfito)-cobalt(III) complexes: Effect of chelate-ring size
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The kinetics of formation of cis-[Co(tn)2(OH2)(OSO2-O)]+ (tn = 1,3-diaminopropane), its acid-catalysed aquation to the parent diaqua complex, anation of trans-[Co(tn)2(OH2)(SO3-S)]+ by N3-, NCS-, SO32--HSO3-, anation of trans-[Co(tn)2(OH)(SO3-S)] by SO32- and acid-catalysed aquation of trans-[Co(tn)2(SO3-S)2]- to the corresponding (aqua)(sulfito-S) complex were investigated and the results compared with analogous data for the corresponding 1,2-diaminoethane (en) complexes. Expanding the chelate-ring size from five to six had virtually no effect on the rate of formation of the sulfito-O complex, but retarded its acid-catalysed aquation. The latter effect was attributed to a pK perturbation; intramolecular hydrogen bonding between the co-ordinated H2O and sulfite in cis-[Co(tn)2(OH2)(OSO2-O)]+ hindered the protonation pre-equilibrium of the sulfito-O complex involved in the acid-catalysed aquation. This is further supported by the fact that there was no ring-size effect on the acid-catalysed aquation of trans-[Co(L-L)2(OH2)(OSO2)]+ (L-L = tn or en). The strong labilising action due to chelatering expansion is remarkably attenuated by the trans effect of S-bonded sulfite as observed in the anation of trans-[Co(L-L)2(OH2/OH)(SO3-S)]+/0. However, trans-[Co(tn)2(OH2)(SO3-S)]+ was found to be prone to intramolecular electron transfer between CoIII and SIV under thermal conditions unlike its en analogue, further reflecting the ring-size effect. Flash photolysis of trans-[Co(L-L)2(OH2)(SO3-S)]+ (L-L = en or tn) generated the transient trans-[Co(L-L)2(OH2)(OSO2)]+. The photochemical ligand isomerisation of both complexes (CoIII-SO3+ → CoIII-OSO2+) also occurred at comparable rates [klso = (4.1 ± 0.8) × 104 and (3.2 ± 1.3) × 104 s-1 at 25°C for the en and tn complexes respectively]. Steady-state photolysis at 254 nm indicated that trans-[Co(en)2(OH2)(SO3-S)]+ underwent photoaquation and photoreduction. Strikingly photoreduction could not be detected for this complex at pH > 8.
- Dash, Anadi C.,Jena, Kishore C.,Roy, Ansuman,Mukherjee, Dipti,Aditya, Sukumar
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p. 2451 - 2461
(2007/10/03)
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- Kinetic Evidence for the Redox Cycling of Manganese(II,III) in the Presence of (1-)ON(NO)SO3(1-) in Aqueous Media
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Redox cycling of Mn(II/III) in the presence of (1-)ON(NO)SO3(1-) in the absence and presence of oxygen was studied by following the increase and decrease of Mn(III) spectrophotometrically as a function of , , and pH.The autoxidation reaction exhibits typical autocatalytic behaviour in which the induction period depends on the concentrations of M(III) and (1-)ON(NO)SO3(1-).Under acidic conditions the reaction does not take place in the absence of Mn(III) or O2.The concentrations of O2, Mn(II) and (1-)ON(NO)SO3(1-) determine whether only oxidation of Mn(II) to Mn(III), or reduction of Mn(III) to Mn(II), or both in one or two redox cycles is observed.Preliminary simulations of some of the observed kinetic traces are presented.
- Prinsloo, Frans F.,Pienaar, Jakobus J.,Eldik, Rudi van
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p. 293 - 300
(2007/10/02)
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- Spectroscopy and Decay Kinetics of the Sulfite Radical Anion in Aqueous Solution
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The sulfite anion, SO3-, has been proposed as a chain carrier in the aerobic free-radical chain oxidation of sulfur dioxide in aqueous solution.The absorption spectrum of SO3- has been obtained following the laser photolysis of argon-saturated sodium dithionate solutions at 193 nm.Using kinetic spectrophotometric and ionchromatographic techniques, it has been shown that the laser photolysis of aqueous dithionate solutions generates both the sulfite anion, SO32-, and the sulfite radical anion, SO3-.The decay of SO3- in aqueous solutions is second-order with an overall rate coefficient of (4.0 +/- 0.4) * 108 dm3 mol-1 s-1 at 293 K in zero ionic strength limit.The reaction proceeds by two channels; recombination to produce dithionate and electron or O- transfer to produce S(IV) and S(VI).SO3- + SO3- -> S2O62-, SO3- + SO3- -> SO32- + SO3.Product analysis gives a value of 0.8 +/- 0.2 for the ratio ka/kb.
- Waygood, Steven J.,McElroy, W. John
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p. 1525 - 1530
(2007/10/02)
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- The Molecular Composition of Hydrophilic Sulfur Sols Prepared by Acid Decomposition of Thiosulfate
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Hydrophilic sulfur sols prepared from sodium thiosulfate and concentrated sulfuric acid and purified by repeated NaCl precipitation and peptization in water have been studied by chemical analysis, vibrational spectroscopy, ion-pair chromatography and reversed-phase HPLC.The composition of the sol is Na1.64S28.6O6*5.9/nSn*1.0NaCl.The elemental sulfur Sn (n = 6-14; mainly S8) accounts for 17 percent the total sulfur; 83 percent of the S are present as long-chain polythionates which form micelles in which the Sn molecules are dissolved.On aging of the sol at 20 deg C the polythionate micelles decompose to give water-soluble short-chain polythionates and elemental sulfur which precipitates from the solution.The micelle structure of hydrophilic sulfur sols may serve as a model for the so-called sulfur globules (S0) formed intra- or extracellularly by many sulfur bacteria which oxidize reduced sulfur compounds to S0. - Infrared and Raman spectra of K2SmO6 (m = 3-6) are reported.The photodecomposition of aqueous tetrathionate yields sulfite, thiosulfate, and polythionates with up to 9 sulfur atoms. - Keywords: Sulfur Sol, Polythionates, Elemental Sulfur, Thiosulfate Decomposition, Sulfur Bacteria
- Steudel, Ralf,Goebel, Thomas,Holdt, Gabriele
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p. 203 - 218
(2007/10/02)
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- pH-Dependent Catalyst-Inhibitor Conversion of Manganese(II) in the Autoxidation of Sulfite
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Manganese(II), a potent catalyst in the low-pH autoxidation of aqueous sulfur(IV), is found to inhibit the high-pH reaction markedly and persistently.The catalyst-inhibitor conversion of manganese occurs at pH 10.1, which is well above the second pKa value of 6.91 for aqueous sulfur(IV).The finding provides the first known evidence that catalyst-inhibitor conversion in liquid-phase autoxidation reaction can occur in polar as well as nonpolar media and that it can be induced by factors other than a variation of the metal concentration.Kinetic evidence suggests the cause of the manganese's conversion into an autoxidation inhibitor at high pH is the formation of a manganese-sulfite radical complex which is unreactive in the propagation chain but active in the termination of the sulfite free radical.The stability constant of the manganese-sulfite radical complex is pH dependent, being higher at higher pH.At a relatively low pH or manganese concentration, the termination of the sulfite radical through the manganese complex is negligible, and manganese functions as a catalyst.However, at high pH, termination of the sulfite radical through the manganese complex becomes dominant, and accordingly, manganese functions as an inhibitor.Additional evidence from other sources supports the postulate that the underlying cause of catalyst-inhibitor conversion in any liquid-phase autoxidation reaction is the ability of the metal ion to tie up and deactivate a radical chain carrier through the formation of a complex which is unreactive in the propagation chain but active in the termination of the radical.Any factors which promote the association of metal ions and radical chain carriers and the destruction of the resulting metal-bound radicals will tend to cause catalyst-inhibitor conversion.These factors are likely to include the metal and initiator concentrations, solution pH and polarity, nature of the metal ion and free radicals, substrate concentration, and temperature.
- Lim, Phooi K.,Hamrick, G. Terry
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p. 1133 - 1136
(2007/10/02)
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- Catalytic Activity of Copper-containing KB-4 Ion Exchangers Towards the Oxidation of Sodium Sulphide by Molecular Oxygen in Aqueous Solution
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The co-ordination complexes of Cu(II) with the KB-4 carboxylic acid ion exchanger have been prepared and studied by chemical, i.r., and ESR spectral methods.In the Cu(II) concentration range 0.05-1.34 mg*equiv g-1 the composition of the co-ordination complexes does not change: Cu(II)(RCCO-)2(RCOOH)2(H2O)2, i.e. four carboxyl groups in a square coplanar configuration, and two water molecules at the apices of the octahedron.The relationship between the composition of the active centre and the catalytic activity of the resin towards the oxidation of sodium sulphide by molecular oxygen has been established.
- Shi, Fung Ti,Astanina, A. N.,Bystrov, T. S.,Volkov, V. I.,Kopylov, V. D.,et al.
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p. 1109 - 1111
(2007/10/02)
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