Towards a simple and precise regulation on the complex electroreduction reactions of gold sulfite ions

Research on Efficient Chlorine Removal via the Synergistic Action of Sulfite and Copper Ions

Sulfite is widely used as a preservative and bleaching agent in food processing, but excessive exposure can pose serious health and environmental risks. In this study, we developed a non-enzymatic electrochemical sensor based on NiO-decorated CuO nanostructures for the sensitive and selective detection of sulfite ions (SO3 2−). CuO nanoflowers were synthesized via a hydrothermal method using various precursor concentrations, with the 2 mM sample exhibiting the highest electrocatalytic performance. Subsequent surface decoration with NiO nanoparticles formed a NiO/CuO composite electrode, which benefited from synergistic interfacial effects and enhanced electron transfer kinetics. The optimized sensor demonstrated a high sensitivity of 74.02 μA mM−1·cm2, a low detection limit of 15.22 μM, and excellent selectivity in the presence of common interfering ions. Notably, the device retained 93% of its initial response after 30 days of ambient storage, indicating good long-term operational stability. These results highlight the NiO/CuO composite as a promising candidate for cost-effective, reliable sulfite detection in food safety and environmental monitoring applications.

Chrysoidine Y dye (CYD) is harmful to aquatic species and human beings, which has the tendency to induce cancer and mutation to living cells. Its degradation is key in creating a healthy environment and curbing pollution. Hence, a stoichiometric method is used to study its degradation with a pool of sulphite ions (SO32-), under a constant ionic strength, [H+], and 449 nm wavelength. The stoichiometry is observed to be 1:1 for CYD: SO32-, which results in the formation of aniline and sulphonic acid as the main products of the degradation. The reaction is first-order with respect to CYD, first-order with respect to SO32-, and a second-order-overall. Increase in the proton concentration impacts positively on the reaction rate of CYD degradation. Negative salt effect is observed as the dilapidation rate of the dye drops. Occurrence of counter ion catalysis is pronounced with large appreciable rate. The participation of a firm intermediate molecule is negative as revealed by the Spectroscopic Scanning Technique (SST) and Michaelis Menten’s Type Plot (MMTP), which cancels the inner-sphere mechanism expectancy. The degradation of the dye was successfully carried out and the reaction points to the outer-sphere mechanism.

Numerical modeling has been used extensively to simulate gas-liquid transfer of sulfur dioxide, assessing how operational parameters affect absorption efficiency in packed or spray columns. Despite individual studies on these contactors, comparative analyses on the same flue gas have been rare. This study uses a numerical model for both packed and spray columns to examine how parameters influence SO2 absorption by sodium sulfite, describing packed and spray columns, is used to investigate the influence of operational parameters on SO2 absorption by sodium sulfite. The model's predictions are validated against experimental data from an industrial pilot plant. Across varying conditions (L/G ratio, temperature, initial SO2 content or initial S(IV) concentration), the packed column achieves higher absorption efficiencies compared to the spray column, with lower assumed energy costs due to a reduced L/G ratio. Temperature proves to be a significant factor, decreasing absorption efficiency by approximately 40% between 40 and 70 °C. SO2 absorption efficiency declines with increasing concentrations of bisulfite and sulfite ions in the absorption solution, dropping to 50% at an S(IV) concentration of 2 kmol m-3 in the liquid phase. Considering the objective of producing a concentrated bisulfite solution and a clean gas, a two-column system is recommended: one for bisulfite solution concentration at acidic pH and the other for gas purification enhancement at basic pH.

Advances in sulphite ion detection via different analytical techniques using modified metal and metal doped metal oxides nanoparticles

Avoiding atmospheric pollution with sulfur dioxide is generally achieved by its absorption from combustion gases in alkaline solutions and conversion to sulfites. Afterwards, sulfites can be transformed into neutral and environmentally safe chemicals by oxidation to sulfates. The oxidation of sulfites to sulfates can also be carried out in a cell in which the fuel will be sulfite ions. In this way, in addition to the beneficial effect of neutralizing large quantities of sulfite waste, electrical energy is also obtained. This is one of the reasons why study of the anodic oxidation of sulfite to sulfate on various electrode materials was necessary. Given the sensitivity of electrode materials in the presence of sulfur compounds, in our research we approached the study of sulfite oxidation on the Incoloy 800 anode in neutral solution (1 mol L−1 Na2SO4). In this research, the results obtained in the study of the kinetic parameters of the anodic process as a function of the sulfite concentration (10−1, 0.5, and 1 mol L−1), using linear voltammetry, are presented. The appreciable values of the exchange current density (3.4, 3.0, and 2.6 A m−2) show that Incoloy 800 has a significant catalytic effect in the anodic oxidation of sulfite. Chronoamperometric studies have shown that the anodic oxidation of sulfite is controlled by the mass transfer of sulfite ions from the bulk solution to the electrode surface. According to the chronocoulometric diagrams, it can be appreciated that, up to anodic potentials of +1.50 V, sulfite oxidation occurs on the electrode, while at more positive potentials, the oxygen evolution reaction is the main process. Electrochemical impedance data provide evidence of a chemical reaction coupled with electron transfer, which was modeled using a Gerischer impedance. At high sulfite concentrations, the charge transfer resistance (Rct) decreases by a factor of 10, indicating that the sulfite oxidation reaction is fast at sufficiently positive potentials. On the other hand, the passivation tendency of stainless steels upon anodic polarization gives them a high corrosion resistance, so that Incoloy 800 can be a viable option as an anode material for sulfite/oxygen (air) fuel cells.

Depression mechanism of sulfite ions on sphalerite and Pb2+ activated sphalerite in the flotation separation of galena from sphalerite

In recent years, transition metal sulfides have been investigated as electrode materials for supercapacitors. Due to their unique crystal structure, morphology and multiple valence states, copper sulfides have high intrinsic electrical conductivity, which is an important requirement for the fabrication of high-performance supercapacitors. The electrochemical mechanism of nanodispersed copper (II) sulfide formation in sulfuric acid medium was studied by voltammetry method. Under voltammetric conditions at a titanium electrode in the presence of divalent copper ions and tetravalent sulfur, the cathodic processes are the reduction of copper ions to the metallic state and sulfite ions to dispersed elemental sulfur. Freshly-formed nanodispersed copper and colloidal sulfur particles chemically interact in the near-cathode space to form univalent copper sulfide. Under galvanostatic conditions on an electrolyzer with a titanium cathode and copper anode, the influence of current density, concentration of electrolyte components on the current yield of nanodispersed univalent copper sulfide was studied. Under optimal electrolysis conditions, the maximum current yield of copper sulfide (II) is 69.86%. The particle size of the obtained copper (II) sulfide, determined using a Hitachi TM-1000 transmission scanning electron microscope, is in the range of 86 nm.

Hydrogen sulfide is a lethal toxic gas that disrupts cellular respiration in the mitochondrial system. Currently, no antidote is available for the clinical treatment of hydrogen sulfide poisoning. In this study, we investigated the function of iron(III)porphyrin complexes as hydrogen sulfide scavengers in water and evaluated their potential use as therapeutic agents for hydrogen sulfide poisoning. The compounds, named met-hemoCD-P and met-hemoCD-I, are composed of iron(III)porphyrin complexed with per-methylated β-cyclodextrin dimers that contain a pyridine (met-hemoCD-P) or imidazole axial fifth ligand that is coordinated to Fe(III) (met-hemoCD-I). These compounds formed stable HS–Fe(III) complexes under physiological conditions, with binding constants of 1.2 × 105 and 2.5 × 106 M–1 for met-hemoCD-P and met-hemoCD-I, respectively. The binding constant of met-hemoCD-I was 10-times higher than that reported for native human met-hemoglobin at pH 7.4 and 25oC. Electron paramagnetic resonance (EPR) spectroscopy and H2S quantification assays revealed that after SH– was coordinated to met-hemoCD-I, it was efficiently converted to nontoxic sulfite and sulfate ions via homolytic cleavage of the HS–Fe(III) bond followed by aerobic oxidation. Mouse animal experiments revealed that the survival rate was significantly improved when NaSH-treated mice were injected with met-hemoCD-I. After the injection, mitochondrial CcO function in brain and heart tissues recovered, and met-hemoCD-I injected was excreted in the urine without chemical decomposition.

The forced oxidation of sulfite ions was conducted to obtain high-quality gypsum in the flue gas desulfurization system. The effects of formic, lactic, acrylic, acetic, propionic, and hexanoic acids added to calcium-based slurry on sulfite oxidation were investigated in this study. Sulfite oxidation was inhibited when the pKa value of organic acids was small or the carbon chain was long. In the identical slurry pH 6, the SO4 2- fractions of slurries with formic and lactic acids, which have the smallest pKa values, were lower than half that of the additive-free slurry. The addition of hexanoic acid with the longest carbon chain showed a similar SO4 2- fraction to that of additive-free slurry. These results indicate that the inhibitory effect on sulfite oxidation is more expressed by the acidity of organic acids. The SO4 2- fraction in the slurry affects the growth and quality of gypsum crystals. The slurry with acetic acid presented the highest SO4 2- fraction and resulted in the formation of high-quality gypsum crystals. The findings of this study can contribute to the selection of organic acid additives with high desulfurization efficiency and the production of high-quality gypsum.

Facile, sustainable, and innovative inclusion of a highly fluorescent isoindole-sulfonate-based probe for the quantification of fluvoxamine, a CNS antidepressant drug; comprehensive method sustainability evaluation

Abstract This paper examined the influence of the sulfite concentration introduced in the electrolyte added to the neutral solution (1 mol L-1 Na2SO4) on the corrosion process of 304L stainless steel material. 304L. The accelerated effect of sulfite ions under corrosion rate of 304L austenitic stainless steel was demonstrated using electrochemical techniques such as linear sweep voltammetry at a low scan rate −1 mV s−1, the Tafel slope method, chronoamperometry, and electrochemical impedance spectroscopy. Electrochemical studies were conducted using a BioLogic SP150 potentiostat/galvanostat. Stainless steels are the most varied and intricate group among all steels. Among them, 304L austenitic stainless steel is one of the most commonly utilized alloys, prized for its excellent corrosion resistance and strength, hygienic and aesthetic properties, affordability, good formability, and effective weldability. [1-3]. In modern industry, the amount of austenitic stainless steel represents only about 2% of the total steel production manufactured globally. This type of steel is commonly employed in chemical engineering, metal extraction, desalination and wastewater treatment plants, the oil and gas sector, transportation and aerospace industries, the food and beverage sector, as well as in architecture and construction engineering. [1].

Modulating the intrinsic fluorescence properties of amoxicillin by sulfur nanodot-based nanoreactor for its direct fluorescence detection

53074 The usefulness of skin prick and patch testing for local anesthetics in clinical practice for patients with sulfite allergy

A simple and efficient chemodosimeter for colorimetric and “turn-on” fluorescent detection of sulphite in aqueous solution

Abstract Sulfites (SO3 2−) are widely used in various industries as a preservative in beverages, pharmaceutical products, wines, foods, and cosmetics. As a preservative, it prevents foods from spoiling and is also used as a bleaching agent due to its antioxidant, anti-browning, and antibacterial activity. Despite its widespread use, inhalation of SO3 2− can lead to health issues such as headaches, nausea, asthma, dizziness, and reduction of red blood cells. Thus, accurate and efficient detection of sulfite is crucial. The deployment of positively charged poly [2-(methacryloyloxy) ethyl] trimethylammonium chloride (PMTC) decorated with gold nanoparticles (AuNPs) offers a novel approach, enhancing sensitivity and specificity in the electrochemical detection of negatively charged sulfite ions (SO3 2−). A sensor for detecting SO3 2− was developed using PMTC decorated with AuNPs on a glassy carbon electrode (GCE). Transmission electron microscopy (TEM) was employed to examine the structural morphology of the composite material, and the formation of AuNPs was confirmed through ultraviolet-visible spectroscopy. Zeta potential analysis affirmed the positive charge of the PMTC composite, highlighting its effective coordination with the negatively charged SO3 2−. The surface conductivity of the modified GCE was studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Kinetic analyses, focusing on scan rate and pH dependencies, elucidated the SO3 2− oxidation dynamics and the interaction between the positively charged PMTC and negatively charged SO3 2−. Quantitative evaluation was performed using the current–time (I-t) technique, achieving a limit of detection of 0.41 ± 0.003 μM (S/N = 3) within a linear range of 6.66 μM to 1020 μM. The modified electrode demonstrated remarkable stability, repeatability, and resistance to common interferents. Real sample analysis using laboratory tap water with a fixed SO3 2− concentration exhibited excellent recovery. The oxidation of SO3 2− on the AuNPs-PMTC-GCE proceeded via first-order kinetics and followed a stepwise pathway facilitated by the charge interactions.

The influence of surface morphology and the oxidation state on the electrocatalytic activity of nanostructured electrodes is well recognized, yet disentangling their individual roles in specific reactions remains challenging. Here, we investigated the electrooxidation of sulfite ions in an alkaline environment using cyclic voltammetry on copper oxide nanostructured electrodes with different oxidation states and morphologies but with similar active areas. To this aim, we synthesized nanostructured Cu films made of nanoparticles or nanorods on top of glassy carbon electrodes. Our findings showed an enhanced sensitivity and a lower detection threshold when utilizing Cu(I) over Cu(II). Density functional theory-based thermochemical analysis revealed the underlying oxidation mechanism, indicating that while the energy gain associated with the process is comparable for both oxide surfaces, the desorption energy barrier for the resulting sulfate molecules is three times higher on Cu(II). This becomes the limiting step of the reaction kinetics and diminishes the overall electrooxidation efficiency. Our proposed mechanism relies on the tautomerization of hydroxyl groups confined on the surface of Cu-based electrodes. This mechanism might be applicable to electrochemical reactions involving other sulfur compounds that hold technological significance.

Sulfite ion and gold (111) surface interaction mechanism

In this study, rhenium nanoparticles were successfully synthesized with precise size control using a water-in-oil microemulsion method under an ambient atmosphere. Spectroscopic characterization using UV-Vis and ESI-MS techniques was used to study the stability of the rhenium(IV) precursor and verify its reduction into rhenium-based nanoparticles. The morphology and size of the rhenium nanoparticles were examined using HR-TEM. The results indicate formation of amorphous rhenium nanoparticles with an average size of 2.2 nm at a water-to-surfactant concentration ratio (W factor) of 10. These rhenium nanoparticles also have good size-stability compared to rhenium colloids generated in water alone. After one week, the particle diameter increased by only 0.6 nm with no evidence of aggregation. An investigation into the effect of various factors on the size and size distribution of the rhenium nanoparticles indicate that the W factor is the most influential parameter (among the considered factors) for size tuning, given that increases in W led to bigger and more polydisperse particles. Additionally, the microemulsion surfactant (AOT) protects the rhenium nanoparticles from their natural tendency to oxidize to perrhenate ion under an air atmosphere. However, a significant consideration in the use of AOT is the previously unreported presence of a chemical impurity which is able to reduce the rhenium(IV) precursor salt and generate rhenium nanoparticles within these microemulsion systems. Our investigation found that this impurity is the sulfite ion which is most likely introduced during manufacturing.