Sulfite Reaction Research Articles

Oxidation Study and Mechanism Analysis of Desulfurization Ash in Dense-Phase Tower

Dense-phase-tower desulfurization technology is an emerging semi-dry flue-gas desulfurization ash process, i.e., the flue gas is allowed to enter the desulfurization tower from the bottom up and, at the same time, is sprayed with a desulfurizing agent that undergoes an acid–base reaction with the flue gas in the ascent process. The calcium sulfite and calcium sulfate produced by the reaction and the part of the desulfurization agent that is not involved in the reaction will enter the subsequent dust removal system, and what is retained is the by-product desulfurization ash. This desulfurization ash contains a large amount of calcium sulfite, which leads to its unstable nature; it is easily oxidized and expands in volume, and, if used in the field of building materials, it will lead to cracking and other problems, so it is difficult to effectively use it. In order to solve this problem, XRF, XRD, and iodometric and other analytical methods were used to determine the specific composition of desulfurization ash, and the muffle furnace and vertical tube furnace were used to study the thermal oxidative modification of calcium sulfite in desulfurization ash, to investigate the effects of the oxygen content, reaction temperature, medium flow rate, and chloride content on the oxidation of calcium sulfite, and to analyze the thermodynamics in the high-temperature oxidation reaction. The results showed that the oxidation rate of calcium sulfite increased with higher reaction temperatures. Increased oxygen content promoted the oxidation rate, particularly at low oxygen levels. The oxidation rate of calcium sulfite correlated positively with the medium flow rate until a rate of 75 mL·min− was reached. At a reaction temperature of 420 °C and a gas flow rate of 85 mL·min−1, the oxidation conversion efficiency exceeded 89%. Chloride content significantly reduced the oxidation rate of calcium sulfite, although this inhibition weakened at temperatures above 500 °C. Kinetic analysis suggested that the oxidation reaction of calcium sulfite predominantly occurred below 500 °C. These findings have both theoretical and practical implications for the thermal oxidation treatment and disposal of desulfurization ash.

Smooth nickel - a suitable anodic material in new alkaline fuel cells sulphite/oxygen

<p>The anodic oxidation of sulphite ions was studied by voltammetric techniques on a nickel electrode in alkaline solution at various concentration of sulphite and polarization rate. The kinetic parameters of the electrode process have been determined using Tafel plots method and a mechanism of the electrochemical oxidation reaction of sulphite has been proposed. Current density, potential range of sulphite electro-oxidation and transformation degree of sulphite ions in the test solutions have been obtained by chronoamperometry and chronocoulometry. The sulphite oxidation mechanism on nickel electrode has been sustained by electrochemical impedance spectroscopy.</p>

Less solvent solid state reaction of sodium sulfite and sulfur

Less solvent solid state reaction of sodium sulfite and sulfur

A Sensitive Chemiluminescence Probe Based on Cerium (IV)-Sulfite Reaction for the Determination of Methamphetamine in Biological Samples and Street Drugs

A Sensitive Chemiluminescence Probe Based on Cerium (IV)-Sulfite Reaction for the Determination of Methamphetamine in Biological Samples and Street Drugs

Cadmium precipitation by sulfite reaction chain under UV irradiation

Cadmium precipitation by sulfite reaction chain under UV irradiation

Kinetics of photolysis and photocatalytic oxidation of ammonium sulfite for hydrogen production

The production of hydrogen via photocatalytic water splitting is one of the most promising technologies for obtaining chemical energy from direct solar energy while maintaining the least possible waste and pollutants. In this paper, we obtain the kinetic parameters necessary for the design of a photoreactor for photolysis and photocatalysis of ammonium sulfite solution. For the case of photolysis, we obtain the kinetics for the effect of changing the pH on the produced amount of hydrogen. For the case of photocatalysis, the intrinsic kinetic parameters of photocatalysis of water splitting reaction of ammonium sulfite and water in the presence of cadmium sulfide as a catalyst under solar radiation was inspected by developing MATLAB codes that can predict the kinetics based on the results of experimental work done. The resulted kinetics are compared to experimental work already done. These obtained kinetic parameters provide guidance for the design or scale-up of a solar photoreactor.

Rhodamine B phenylhydrazide as a new chemosensor for sulfite quantification: Application to food samples

A simple and sensitive spectrophotometric method for the quantification of sulfite at trace level has been proposed. The method is based on the change in the intensity of the color developed on reaction of sulfite with Rhodamine-B Phenyl hydrazide (RBPH) in aqueous micellar medium. The experimental conditions such as pH, concentration of RBPH and Tween 80 have been optimized and calibration plot has been constructed. The proposed method offers a wide linearity in the concentration range 0–15 ppm of sulfite. The limit of detection and limit of quantification were found to be 0.006 and 1.5 ppm respectively, with the regression co-efficient R2 = 0.992. The proposed method has been successfully applied to measure the trace level sulfite in food samples such as tomato ketchup, jam, dry grapes, sugar and wine. Comparison of the developed method with standard protocol showed good recoveries.

Destruction of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment.

Ultraviolet photochemical reaction of sulfite (SO32-) photosensitizer generates strongly reducing hydrated electrons (eaq-; NHE = -2.9 V) that have been shown to effectively degrade individual per- and polyfluoroalkyl substances (PFASs), including perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). However, treatment of complex PFAS mixtures in aqueous film-forming foam (AFFF) remains largely unknown. Here, UV-sulfite was applied to a diluted AFFF to characterize eaq- reactions with 15 PFASs identified by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) targeted analysis. Results show that reactivity varies widely among PFASs, but reaction rates observed for individual PFASs in AFFF are similar to rates observed in single-solute experiments. While some structures, including long-chain perfluoroalkyl sulfonic acids (PFSAs) and perfluoroalkyl carboxylic acids (PFCAs) were readily degraded, other structures, most notably short-chain PFSAs and fluorotelomer sulfonic acids (FTSs), were more recalcitrant. This finding is consistent with results showing incomplete fluoride ion release (up to 53% of the F content in AFFF) during reactions. Furthermore, results show that selected PFSAs, PFCAs, and FTSs can form as transient intermediates or unreactive end-products via eaq- reactions with precursor structures in AFFF. These results indicate that while UV-sulfite treatment can be effective for treating PFOS and PFOA to meet health advisory levels, remediation of the wider range of PFASs in AFFF will prove more challenging.

Brown Carbon Production by Aqueous-Phase Interactions of Glyoxal and SO2.

Oxalic acid and sulfate salts are major components of aerosol particles. Here, we explore the potential for their respective precursor species, glyoxal and SO2, to form atmospheric brown carbon via aqueous-phase reactions in a series of bulk aqueous and flow chamber aerosol experiments. In bulk aqueous solutions, UV- and visible-light-absorbing products are observed at pH 3-4 and 5-6, respectively, with small but detectable yields of hydroxyquinone and polyketone products formed, especially at pH 6. Hydroxymethanesulfonate (HMS), C2, and C3 sulfonates are major products detected by electrospray ionization mass spectrometry (ESI-MS) at pH 5. Past studies have assumed that the reaction of formaldehyde and sulfite was the only atmospheric source of HMS. In flow chamber experiments involving sulfite aerosol and gas-phase glyoxal with only 1 min residence times, significant aerosol growth is observed. Rapid brown carbon formation is seen with aqueous aerosol particles at >80% relative humidity (RH). Brown carbon formation slows at 50-60% RH and when the aerosol particles are acidified with sulfuric acid but stops entirely only under dry conditions. This chemistry may therefore contribute to brown carbon production in cloud-processed pollution plumes as oxidizing volatile organic compounds (VOCs) interact with SO2 and water.

A chemiluminescence reaction consisting of manganese(IV), sodium sulfite, and sulfur- and nitrogen-doped carbon quantum dots, and its application for the determination of oxytetracycline.

Sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) were prepared by a solid-phase hydrothermal method from cysteine and citric acid and characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and FTIR spectroscopy. These QDs were exploited as enhancers to amplify the chemiluminescence (CL) of manganese(IV)-sodium sulfite reaction. S,N-CQDs exceptionally enhanced the CL intensity of this system, around 900-fold. This effect was attributed to the energy transfer from SO2*, produced by reaction of Mn(IV) with SO32-, to S,N-CQDs. The maximum wavelength of CL emission was 480nm, which confirmed that the final emitting species was S,N-CQDs. After optimization of reaction conditions, the analytical applicability of S,N-CQD-Mn(IV)-SO32- CL system was studied. In the presence of oxytetracycline, the CL intensity was significantly diminished. A linear relationship was observed between CL signal and the logarithm of oxytetracycline concentration in the range of 0.075-3.0μM with a detection limit of 25nM. This CL assay for oxytetracycline was used for analysis of spiked milk and water samples. Graphical abstractSchematic representation of the amplified chemiluminescence (CL) reaction consisting of sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) Mn(IV) and Na2SO3. Sub-micromolar levels of oxytetracycline can be determined by using this system.

Study of the toxicological characteristics of water-soluble surface-active substances obtained based on phenol, formaldehyde and sodium sulphite

The object of research is the products of the condensation reaction of phenol, formaldehyde and sodium sulfite in an aqueous medium, in order to obtain water-soluble non-toxic products based on it, which can be proposed for use as surfactants. In the course of the study, the effect of the reaction conditions (ratio of components, temperature and process time) on the quality of the products obtained and their toxicological characteristics are studied. The optimal ratio of the starting reagents phenol: formaldehyde: sodium sulfite: water is selected, which allows to obtain a product with surface-active properties and which contains substances that can be harmful to health. It is recommended that the condensation process be carried out within 1 hour, the optimum reaction temperature is selected at 130 °C. The qualitative characteristics of the obtained product allow to recommend its use as an anionic surfactant. For this, the symptomatic and toxicological properties of the newly developed surfactant, the product of the condensation of phenol, formaldehyde and sodium sulfite in an aqueous medium, are studied. Based on the studies, it is found that with the introduction of such surfactants into the stomach of experimental white rats-females, their slightly irritating effect on the mucous membranes and skin is observed. According to the mortality criterion, with a single oral administration (LD50), the harmful effects of the substance on rats are not noted. According to the research results, the product can be attributed to class IV hazard (low hazard substances) according to GOST 12.1.007.According to toxicological findings, the resulting product can be recommended for use as a textile auxiliary substance, in the technological operations of bleaching, dyeing and printing of fabrics in contact with human skin, as well as additives to concrete mixtures used in the construction industry and other industries

Modulation Effects of Permanganate and Manganese(II) Ions on the Oscillatory Dynamics in a Bromate-Sulfite Reaction System.

It is important to study nonlinear dynamical systems showing pH and temperature oscillations simultaneously. Here, we systematically investigated the bromate-sulfite reaction in its coupled system. Large-amplitude temperature oscillations could be measured accompanied by the pH oscillations with or without permanganate and manganese(II) ions. The modulation effects on the oscillatory dynamics of the bromate-sulfite reaction system produced by permanganate and manganese(II) ions were investigated in detail. On the one hand, with permanganate, an additional negative pH feedback process between permanganate and bisulfite occurs, leading to weakening the pH positive feedback. The above opposite effects make the period length change unmonotonically when adjusting the permanganate concentration and flow rate. On the other hand, with Mn2+ as the feedback agent, the nonmonotonic change of period was not obvious because it only contained one feedback loop, which can only reinforce negative feedback without affecting positive feedback.

Insights into the Oxidation of Organic Cocontaminants during Cr(VI) Reduction by Sulfite: The Overlooked Significance of Cr(V).

Literature works reported that organic cocontaminants could be degraded during Cr(VI), a contaminant, reduction by sulfite (Cr(VI)/sulfite process). However, the role of Cr(V) and Cr(IV) intermediates in the Cr(VI)/sulfite process has been overlooked. In this study, we confirmed the generation of Cr(V) and proposed a new mechanism for the decomposition of coexisting organic contaminants during Cr(VI)/sulfite reactions occurring in oxygenated solutions at pHini 4.0 with the molar ratio of sulfite to Cr(VI) of 10.0. UV-visible and electron paramagnetic resonance (EPR) spectra indicate that Cr(V) was the predominant Cr intermediates in oxygenated solutions, while Cr(IV) accumulated in deoxygenated solutions. The contribution of Cr(V) to the degradation of organic contaminants was verified by the EPR spectra collected at 2 K and using methyl phenyl sulfoxide as a probe compound. Both Cr(V) and SO4•- contributed to the decomposition of organic contaminants in oxygenated solutions, with the relative contributions from each species being strongly dependent on properties of the target organic cocontaminants. The key mechanisms responsible for Cr(V) accumulation were supported by DFT calculations, and the degradation kinetics of organic cocontaminants was simulated with the program Kintecus 6.51. This work advances the fundamental understanding of the oxidative transformation of coexisting organic contaminants in this process.

Synthesis of cleavable silicone surfactant for water-repellent application

Polymeric silicone-based surfactants were prepared by the reaction of polyethylene glycol, maleic anhydride, polydimethylsiloxane, silicone oil, titanium isopropoxide, and sodium hydrogen sulfite. These surfactants showed water-repellent properties when cleaved by different buffer solutions. The synergetic effect of silicone oil-based surfactants and siloxane-based surfactants was studied using different characterization techniques for the surfactants. The hydrophobic properties of cleaved silicone-based surfactants were studied by measuring the contact angle measurement. The polymeric silicone surfactants are stable in nature. The structures of various stages of reaction were confirmed by thin-layer chromatography, Fourier-transform infrared spectroscopy, ultraviolet spectra, and nuclear magnetic resonance analysis. The surface-active properties of surfactants like surface tension and critical micelle concentration as well as foaming and wetting characteristics were also studied. This water-soluble surfactant had low foaming properties and can be used in textile, agriculture, petroleum and paint industries. The cleaved form of silicone surfactant was used for water-repellent application in textile and paint industries.

Electrolysis-Assisted Mn(II)/Sulfite Process for Organic Contaminant Degradation at Near-Neutral pH

Manganese-catalyzed sulfite activation (i.e., Mn(II)/sulfite) has emerged as an advanced oxidation process to produce sulfate radical (SO4•−) for water treatment. However, to maintain the catalytic activity of Mn(II) ion, solution acidity has to be kept below pH 4, which is difficult to maintain in practice. Moreover, Mn(II)/sulfite reaction is a strongly oxygen-dependent process, and purging air into reaction solution is another extra cost. To solve the above issues, we devised to implement electrolysis into Mn(II)/sulfite (i.e., electro/Mn(II)/sulfite process) for organic compound (bisphenol A, BPA) oxidation. It was revealed that, under near-neutral conditions (pH 6), the removal rate of 10 μM BPA was increased from 46.3%, by Mn(II)/sulfite process, to 94.2% by electro/Mn(II)/sulfite process. The enhancement of BPA removal after implementation of electrolysis to Mn(II)/sulfite process was investigated, and concluded to be a result of several pathways. In detail, the produced oxygen from water electrolysis, direct sulfite oxidation on anode, and local acidic pH at anode vicinity together play a role in promoting SO4•− production and, therefore, contaminant removal. Radical-scavenging assays confirmed the dominant role of SO4•− in electro/Mn(II)/sulfite process.

New Insights into the Cystine-Sulfite Reaction

The mechanism by which cysteine-S-sulfate is formed from the reaction of sulfite with cystine in the absence of a dedicated oxidizing agent is investigated using high-resolution NMR. Changes to reactant ratio, pH, UV light exposure and temperature were evaluated to determine the most effective conditions to achieve the maximum yield of cysteine-S-sulfate without recourse to conventional oxidizing reagents. Herein evidence is provided for both nucleophilic and radical mechanisms, by which cysteine-S-sulfate can be generated with yields of up to 96%.

Radiosynthesis of O-(1-[18 F]fluoropropan-2-yl)-O-(4-nitrophenyl)methylphosphonate: A novel PET tracer surrogate of sarin.

O-(1-Fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate is a reactive organophosphate ester (OP) developed as a surrogate of the chemical warfare agent sarin that forms a similar covalent adduct at the active site serine of acetylcholinesterase. The radiolabeled O-(1-[18 F]fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate ([18 F] fluorosarin surrogate) has not been previously prepared. In this paper, we report the first radiosynthesis of this tracer from the reaction of bis-(4-nitrophenyl) methylphosphonate with 1-[18 F]fluoro-2-propanol in the presence of DBU. The 1-[18 F]fluoro-2-propanol was prepared by reaction of propylene sulfite with Kryptofix 2.2.2 and [18 F] fluoride ion. The desired tracer O-(1-[18 F]fluoropropan-2-yl)-O-(4-nitrophenyl) methylphosphonate was obtained in a >98% radiochemical purity with a 2.4%±0.6% yield (n=5, 65minutes from start of synthesis) based on starting [18 F] fluoride ion and a molar activity of 49.9GBq/μmol (1.349±0.329Ci/μmol, n=3). This new facile radiosynthesis routinely affords sufficient quantities of [18 F] fluorosarin surrogate in high radiochemical purity, which will further enable the tracer development as a novel radiolabeled OP acetylcholinesterase inhibitor for assessment of OP modes of action with PET imaging in vivo.

Solar-Driven Photocatalysis for Wastewater Treatment Promoted by Sulfite Addition

Solar-driven heterogeneous photocatalysis is considered a promising technique for degradation of organic pollutants in wastewater. Visible light from the solar spectrum is however not efficiently utilized in photocatalysis. In this work, we have developed a sulfite-enhanced visible-light-driven photocatalysis process using BiOBr as the model photocatalyst and methyl orange (MO) as the model organic pollutant. We found that the degradation rate of MO was improved by 29 times in the presence of 20 mM sulfite, and the enhancement increased with the concentration of sulfite. Studies using hole scavengers suggest that sulfite radicals generated by the reactions of sulfite (sulfite anions or bisulfite anions) with holes or hydroxyl radicals are the active species for MO photodegradation using BiOBr under visible light. In addition to the BiOBr/MO system, the sulfite-assisted photocatalysis approach has been successfully demonstrated in a variety of photocatalysis systems including BiOBr/rhodamine B (RhB), BiOBr/phenol, BiOI/MO, and Bi2O3/MO systems under visible light irradiation, as well as in TiO2/MO system under simulated sunlight irradiation. The developed method implies the potential of introducing external active species to improve photocatalytic degradation of organic pollutants.

Rapid degradation of brominated and iodinated haloacetamides with sulfite in drinking water: Degradation kinetics and mechanisms

The effective removal of haloacetamides (HAMs) as a group of emerging disinfection by-products is essential for drinking water safety. This study investigated the degradation of 10 HAMs, including chlorinated, brominated, and iodinated analogues, by sodium sulfite (S(IV)) and the mechanism behind it. The results indicated that all HAMs, excluding chlorinated HAMs, decomposed immediately when exposed to S(IV). The reductive dehalogenation kinetics were well described by a second-order kinetics model, first-order in S(IV) and first-order in HAMs. The degradation rates of HAMs increased with the increase of pH and they were positively correlated with sulfite concentration, indicating that the reaction of S(IV) with HAMs mainly depends on sulfite. The rank order and relative activity of the reaction of sulfite with HAMs depends on bimolecular nucleophilic substitution reaction reactivity. The order of the reductive dehalogenation rates of HAMs versus the substitution of halogen atoms was iodo- > bromo- >> chloro-. During reductive dehalogenation of HAMs by sulfite, the α-carbon bound to the amide group underwent nucleophilic attack at 180° to the leaving group (halide). As a consequence, the halide was pushed off the opposite side, generating a transition state pentacoordinate. The breaking of the C-X bond and the formation of the new C-S bond occurred simultaneously and HAM sulfonate formed as the immediate product. Results suggest that S(IV) can be used to degrade brominated and iodinated HAMs in drinking water and therefore should not be added as a quenching agent before HAM analysis to accurately determine the HAM concentrations produced during water disinfection.

Effects of Hydrogen Bond Donors on Reactivity of Sulfite Oxidase

Sulfite oxidase (SO) catalyzes the conversion of sulfite to sulfate as the last step in the degradation of cysteine and methionine [1]. Severe neonatal neurological problems are caused by SO deficiency in humans [2]. The overall mechanism of SO suggested that the reductive half reaction of SO is the rate limiting step for enzyme activity [3]. Using a computational approach, first I will study the elementary steps for the half reaction to determine the rate limiting step, then by introducing mutations in the active site of SO I will determine the effects of the hydrogen donors present in the active site.SO is part of the Molybdenum cofactor family of enzymes as it contains a mononuclear Molybdenum (Mo) that is penta‐coordinated [4]. At the Mo active site, the reductive half reaction of sulfite to sulfate takes place in two steps. The first step is a nucleophilic attack by the sulfite ion to the equatorial oxygen group. The second step is the release of sulfate facilitated by the spectator oxygen group [4]. By determining the energy profiles for both steps in this reaction I will determine which step is rate limiting and determine the route, associative or dissociative interchange, of the reaction.Model enzyme complexes have suggested that hydrogen donors in the active site play a key role in mediating this reaction. In previous studies performed we determined that the product release step is facilitated by pyridinium a hydrogen donor for the reaction. Pyridinium lowers the activation energy for the product release step (ΔH~ 30 kJ/mol) and promotes a dissociative interchange reaction route. In this study I will determine if hydrogen donors in the Mo active site behave as pyridinium does in the model enzyme complexes.Using Gaussian ONIOM to perform QM/MM calculations for the reaction of sulfite to sulfate catalyzed by SO, I will determine the energy profile of the reaction to identify the rate limiting step and the role of possible hydrogen donors in the active site of SO by comparing the reaction mechanism of two variants of SO with wild type SO. The variants will demonstrate the role as possible hydrogen bond donors of Tyrosine and water that are located in the active site of MO.The role of sulfite oxidase is crucial to the degradation of sulfite in the body and prevention of the accumulation of toxic sulfite in the body. Understanding how SO functions at a molecular level is crucial for the design and implementation of treatment for SO deficiency. The elementary steps of the enzyme activity can help determine specific roles of key residues in the enzyme. These steps cannot be seen in large scale enzyme kinetics studies, but computational studies allow the study of small movements and allow the study of these small‐scale reaction mechanics.Support or Funding InformationLouis Stokes Alliance for Minority Participation (LSAMP) HRD # 1305011This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.