Oxidation Of Sulfite Ions Research Articles

Electrochemical oxidation of sulfite ions in aqueous solutions

Gaseous pollutants that affect human health, destroy vegetation and damage materials and art treasures can be converted into harmless components by electrochemical reactions. Electrochemical gas purification methods can be applied basically in two steps. In the first step, gases to be removed are absorbed in an aqueous electrolyte. Then, in the second step, they can be converted into harmless components via electrochemical oxidation or electrochemical reduction. This study investigated the feasibility of electrochemical removal of sulfite ions arising from the absorption of sulfur dioxide in an aqueous electrolyte. The removal efficiency, current efficiency, and energy consumption were determined at different initial sulfite ion and electrolyte concentrations and applied currents. Furthermore, linear sweep voltammetry studies were performed using a graphite electrode in sulfuric acid. It has been concluded from all these experiments that sulfur dioxide can successfully be removed using an electrochemical method.

Effect of Mn2+ on Sulfite Oxidation in Limestone Scrubbing

Although it has been already reported that manganese plays an important role in the oxidation of sulfite ion, the influence has not yet been understood exactly and the oxidation rates reported in the existing investigations are much lower than those estimated from the performance of actual FGD systems. Manganese compounds are usually contained in raw limestone as the trace element, and concentration of Mn2+ in the absorption slurry is of several ppm. It was found in this investigation that Mn2+ ion is inevitable for the oxidation of Ca(HSO3)2, the oxidation rate in the homogeneous liquid phase is proportional to the [Mn2+]2 and 10(0.1038pH), and the oxidation rate of Ca(HSO3)2 is about 16 times as high as that of H2SO3. It is further predicted that the limited absorption rate of oxygen into the absorption calcium slurry makes the oxidation rate appear linearly dependent on the partial pressure of oxygen in the flue gas and does not depend on Mn2+ concentration as the Mn2+ concentration is so high that the...

CdS Nanoparticle Photocatalysis of the Chain Oxidation of Sulfite Ions by Molecular Oxygen

High photocatalytic activity was found for colloidal cadmium sulfide nanoparticles in the radical chain oxidation of sulfite ions by molecular oxygen in aqueous solution. The kinetics of this reaction was studied and a mechanism was proposed, which is in satisfactory accord with the experimental data.

Determination of Antioxidants in Biological Objects by Measuring the Kinetics of Free-Radical Oxidation of Sulfite Ions

Antioxidants exhibiting hydrophobic properties can be quantitatively determined by methods based on hydrocarbon oxidation models. This problem was reviewed in a number of papers and monographs [1 – 4]. At the same time, the task of determining antioxidants in aqueous media is still incompletely solved. Indeed, methods employing models of free-radical decomposition of hydrogen peroxide with chemiluminescent detection [5] are inconvenient in practice because of the instability of the main substrate (hydrogen peroxide). Judging the antioxidant activity of a given agent by quenching of radical-induced chemiluminsecence can also be ambiguous [6]. The purpose of this study was to develop a method for the quantitative determination of water-soluble antioxidants in biological objects, based on a model of the free-radical oxidation of a sodium sulfite solution purged with oxygen. Within the framework of this work, we (i) developed a method of kinetic measurements for determining water-soluble antioxidants based on a model of the free-radical oxidation of sodium sulfite in solution and (ii) applied this method to the analysis of biological objects (medicinal plants).

Anodic oxidation of sulphite ions on graphite anodes in alkaline solution

The anodic oxidation of sulphite ions in alkaline 1 M Na2SO4 solution on graphite rotating disc electrodes has been studied over the range from 25 to 60 °C. The reaction order with respect to sulphite ions is below 1 at low potentials and 1 at high potentials. The reaction order with respect to hydroxide ions is close to zero. Two Tafel slopes were observed, 0.060 V decade−1 at low potentials and 0.190.20 V decade−1 at high potentials. The reaction activation energy was calculated at different potentials. The results obtained, using the potential sweep method, are consistent with those realized using the rotating disc. A possible reaction mechanism has been proposed and the diffusion coefficients of sulphite ions and the diffusion activation energy have been calculated.

The Role of Reducing Agent in Oxidation Reactions of Water on Illuminated TiO2 Electrodes

Oxidation of water on an illuminated electrode was investigated using a rotating ring‐disk electrode, focusing on the role of the reducing agent, , added in solution. The disk was illuminated with a chopped‐light source, and the corresponding ring response at the Pt‐ring, , was recorded. Although oxidation products were expected to be produced on the disk surface and carried to the ring electrode, was found to be negative in dilute solution even at large negative potentials, e.g., −0.8 V vs. SCE. This phenomenon was observed in neutral and basic solutions. It is proposed that radical is formed at an illuminated ‐disk and subsequently initiates a homogeneous free‐radical chain oxidation of sulfite ion. This chain reaction consumes oxygen to be supplied from the solution via the disk to the ring, reducing the ring current associated with the reduction of oxygen. As a result, the ring current is lower under illumination than in the dark.

Photo-oxidation of sulfite ions in the presence of some iron oxides

The photocatalytic oxidation of sulfite ions over different iron oxides samples is investigated. For the different hematite samples tested, the experimental data of sulfite photo-oxidized vs. irradiation time can be adjusted fairly well to a kinetic equation of the type dx/dt = K(1−x)/x, where x is the fraction of sulfite reacted at time t. The behaviour described by this equation corresponds to an heterogeneous process where the product of reaction is strongly adsorbed on the substrate. The rate constant K obtained for the different hematite samples can be related to their respective specific surface area. Fe(II) species were detected in solution when hematite suspensions were irradiated. These Fe(II) ions are assumed to be formed through photoreduction of lattice Fe(III). On the contrary, for magnetite and maghemite suspensions no Fe(II) ions were detected in solution after irradiation. In the latter case, crystalline phase transformation is assumed to take place.

Electrochemical oxidation of sulphite ions at graphite electrodes

The electrochemical oxidation of sodium sulphite has been studied in aqueous sodium sulphate solution at two different graphite electrodes, one being of natural graphite (EC) and the other impregnated with phenol (ECK). The objective of the present work was to obtain some insight into the direct oxidation as well as the indirect oxidation, via produced oxygen radical species, of sulphite on non-metal electrodes. For this reason a study of the oxidation of sulphite in the concentration range between 0–0.10m in aqueous sodium sulphate using a batch electrochemical reactor, operating potentiostatically, was undertaken. The potential range was chosen between 1.0 to 2.5 V/SCE, and the concentration of the supporting electrolyte, sodium sulphate, was kept constant at 0.5m. A kinetic Tafel type law, considering irreversible behaviour for the direct sulphite oxidation and the mass transfer performance in regards to the experimental conditions were applied to predict the time variations of the sulphite conversion.

Catalytic activity of cobalt(II) tetrasulphophthalocyanine for the oxidation of sulphite ions and other substrates by dioxygen

The oxidation of sulphite ions by dioxygen in the presence of cobalt(II) tetrasulphophthalocyanine (CoTSP) is catalyzed by traces of metal ions in the system and not by the complex itself. The addition of EDTA completely suppresses the oxidation of sulphite ions even in the presence of CoTSP. When the oxidation of a substrate is actually catalyzed by CoTSP, EDTA has no effect on the reaction rate. The catalytic effect of CoTSP is observed if the substrate and the catalyst form a reactive binary adduct, CoTSP substrate, responsible for an absorption band near 450 nm.

Short-lived manganate(VI) and manganate(V) intermediates in the permanganate oxidation of sulfite ion

La reaction globale entre pH 8 et 12 est: 2MnO 4 − +3SO 3 2− +H 2 O→2MnO 2 +3SO 4 2− +2OH − ; elle consiste en 2 etapes: accumulation et disparition de M 4 O 4 2−

Measurement of interfacial area in bubble columns by the sulphite method

The reaction rate constant and the reaction order with respect to oxygen and sulphite are determined in the paper from the rate of absorption of oxygen into aqueous sulphite solutions catalyzed by cobalt ions. The measurements were carried out in a mixed cell with quiescent liquid level. The utility of the results is discussed for the measurement of interfacial area in bubble columns. The knowledge of the interfacial area is important both for design and calculation of chemical gas-liquid reactors. A most convenient method of determining this parameter is indirect evaluation from the absorption rates of a suitable model reaction. With regard to the various requirements put on such reaction (the knowledge of the reaction mechanism and kinetics, reasonable costs of the chemicals used for large-scale experiments) the choice is rather limited. The study of such model reactions has been the subject of numerous papers; the most significant ones are summarized in the monograph by Danckwerts 1. The often cited reaction is oxidation of sulphite ions by oxygen catalyzed by salts of heavy metals. The reaction scheme may be written as'

Reactions in fused salts. VII. Oxidation of sulphite ions with oxygen in a melt of eutectic mixture of lithium and potassium chlorides

Reactions in fused salts. VII. Oxidation of sulphite ions with oxygen in a melt of eutectic mixture of lithium and potassium chlorides

Destruction of tryptophan during the aerobic oxidation of sulfite ions

Tryptophan was rapidly destroyed aerobically in the presence of Mn 2+ and sulfite. The rate of destruction was greatly increased when horseradish peroxidase was added. The optimal pH for the reaction was 8.0. The destruction of tryptophan was dependent on the aerobic oxidation of sulfite. Superoxide dismutase inhibited sulfite oxidation and thus inhibited the tryptophan destruction. Tracer studies indicate that tryptophan is converted into at least 4 products.

The sulfite-activated oxidation of reduced pyridine nucleotides by peroxidase

1. 1. The aerobic oxidation of sulfite ions is initiated by peroxidase in the presence of Mn ++ or certain phenolic compounds such as thyroxine or estradiol. An inhibition of sulfite oxidation by the peroxidase-thyroxine-O 2 system was produced by epinephrine, glutathione, sodium thiosulfate, ascorbic acid, catalase and reduced diphosphopyridine nucleotide. 2. 2. The oxidation of reduced diphosphopyridine nucleotide (or reduced triphosphopyridine nucleotide) by horseradish peroxidase, Mn ++ and oxygen is stimulated by sulfite ions. Hemoglobin, myoglobin, myeloperoxidase, a uterine homogenate and relatively large concentrations of inorganic iron can replace horseradish peroxidase in this reaction. Sulfite was most effective when cacodylate, phosphate, and to a lesser extent, arsenate buffers were employed, and was less effective in the presence of Tris, glycylglycine, or imidazole buffers at pH 7.0. The sulfite-activated oxidation of reduced diphosphopyridine nucleotide was inhibited by copper, hydrogen peroxide, sodium thiosulfate, glutathione, epinephrine, and ascorbic acid. 3. 3. Sulfite and thyroxine, or sulfite and estradiol have a synergistic effect on the oxidation of reduced diphosphopyridine nucleotide by the Mn ++-peroxidase-O 2 system. Sulfite ions have been employed in this way to magnify the response of the uterine enzyme to thyroxine and estradiol.

The Rate of Oxidation of Sulfite Ions by Oxygen

The Rate of Oxidation of Sulfite Ions by Oxygen