Sulfite Research Articles

A fluorescent probe based on BODIPY for hydrogen sulfide imaging in living cells and zebrafish

A novel fluorescent probe based on 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) structure as fluorophore with 7-nitro-1,2,3-benzoxadiazole (NBD) served as detection unit was designed for specific and sensitive detection of H2S in living cells and zebrafish. In this work, we prepared a novel fluorescent probe for detection of hydrogen sulfide with strong fluorescent enhancement, good biocompatible and excellent specifically detection. The probe 1 displayed emission at 580 nm with excited wavelength at 530 nm in aqueous solution which organic proportion was only 10%. This probe exhibits highly selectively and specifically to detect H2S compared with other related interferences including sulphur-amino acids, sulfite ion and cations. In the addition of H2S into the detection system, the fluorescent intensity was sharply increased about 170-fold with the limitation detection as low as 16.8 nM. The sensing mechanism was through the cleave reaction between analyte and NBD unit which was characterized by high resolution mass spectrum (HRMS). This platform also permits low biotoxicity which can successfully be utilized to evaluate the concentration level of H2S and imaging in living cells and zebrafish.

Incorporation of desulfurization wastewater to achieve ultra-low energy consumption in electrochemical lead recycling

Cleaner and more cost-effective battery recycling techniques are still in demand for improving battery's sustainability. Herein, a novel electrochemical spent lead-acid battery recycling approach with ultra-low energy consumption is proposed in this work, which is achieved via coprocessing with desulfurization wastewater. Desulfurization wastewater (containing sulfite ion, SO32−) is used as reducing agent for lead paste leaching process and electrolyte for the subsequent solid-state electrolysis process respectively, while the wastewater can be effectively treated. Morphology and crystal structure characterizations indicate the lead paste leached by simulated desulfurization wastewater is mainly composed of lead suboxide (Pb2O). Electrochemical analyses reveal that charge demand for cathodic electro-reducing desulfurization wastewater leached lead paste into metallic lead is significantly lower than original lead paste. Furthermore, sulfite ion is oxidated on anode during the solid-state electrolysis process, thereby decreasing the anodic potential compared to the traditional oxygen evolution reaction. Thus, the introduction of desulfurization wastewater significantly reduces the overall energy consumption of the solid-state electrolysis by influencing both of the anodic and cathodic processes. The energy consumption to recycle a ton of lead is 169.8–230.5 kWh under optimized operation conditions, which is only 21.2–51.8% of the traditional electrochemical lead recycling process, while 1.6–1.8 m3 desulfurization wastewater with 50,000 mg L−1 chemical oxygen demand can be treated. Therefore, the co-processing of spent lead-acid battery and desulfurization wastewater is proven to be a win-win waste disposal strategy.

Anodic sulphite oxidation on lead electrode in a neutral environment

The purpose of the research, anodic oxidation of the sulphite ions on the lead electrode in neutral solution, is both to establish the mechanism of sulphite electrooxidation on lead electrode and to determine the optimal parameters for the anodic process. The work started from the premise that the electrodes used in the anodic electrode processes that are carried out in aqueous solutions must have catalytic properties for the oxygen evolution release reaction. Among the metals tested as possible anodes to equip the electrochemical reactors used to obtain oxygen electrochemically from alkaline and acid electrolyte solutions, platinum exhibits the highest catalytic activity. Due to both the high price and the existence of a limited quantity of this metal, researches have been focused on identifying other metals and metal alloys that have catalytic properties for anodic processes [1].The electrochemical behaviour of the sulphite ions in the test solutions was studied by cyclic and linear voltammetry. The Tafel plot method was applied for a complete characterization of the process studied at the lead electrode / neutral electrolyte interface and for the determination of kinetic parameters (current density io and anode transfer coefficient α) [2]. The chrono-electrochemical methods (chronoamperometry, chronocoulometry) were chosen to determine the optimal parameters of the studied oxidation process (current density, optimal range of specific oxidation potential for sulphite electrooxidation and degree of transformation of sulphite ions in test solutions) [3].The presented studies regarding the electrochemical behaviour of sulphite ions in neutral medium on lead electrodes, are the initial point for the development of a Na2SO3 / O2 fuel cell [3].

Desulfurization characteristics of limestone slurry with added organic acid

In this study, a desulfurization experiment was performed in a bubbling reactor to investigate the effects of adding organic acids, such as formic, acetic, propionic, lactic, oxalic and adipic acid, to limestone slurries. The limestone slurries added these organic acids were referred to as FAS, AAS, PAS, LAS, OAS, and ADS, respectively. Flue-gas desulfurization characteristics varied with the acidity of organic acid additives. The T99 of slurries increased with pKa of the organic acids because slurry pH was high in the early phase of absorption which increased the time to reach the slurry pH range (4.1–4.6) required for the T99 end. During SO2 absorption, the sulfate ion fraction was ≥0.5 in PAS, AAS, and ADS, with pKa > 4, but <0.5 in LAS and FAS with pKa < 4. PAS, AAS, and ADS supported the oxidation of sulfite ions, whereas LAS and FAS suppressed it. [H+] × [A−] increases with decreasing pKa of organic acids. Therefore, [H+]slurry and [A−]slurry in the slurry may be engaged in the oxidation of sulfite ions; consequently, increasing [H+] × [A−] inhibited the oxidation of sulfite ions. The sulfate ion fraction affected gypsum dehydration following completion of SO2 absorption. After drying at 60 °C, LAS and FAS (sulfate ion fraction < 0.5) formed only gypsum, whereas PAS, AAS, and ADS (sulfate ion fraction ≥ 0.5) formed both gypsum and anhydrite. Accelerated oxidation of sulfite ions with sulfate ion fraction ≥ 0.5 during slurry drying after reaction completion produced a sulfuric acid solution with a high sulfate ion concentration, which reduced the temperature of gypsum dehydration.

Electrochemical Sulfite‐Ion Sensor Using Sm2CuO4‐Based Layered Perovskite‐Type Oxide Thick Film

Sm2−xCexBO4 (x = 0, 0.1; B = Fe, Cu) thick films were prepared by an electrophoretic deposition method and applied as sulfite‐ion (SO32−) sensors. Among the oxides, Sm1.9Ce0.1CuO4 showed good amperometric response to sulfite ions in the ion concentration range between 1.0 × 10−5 and 1.0 × 10−4 M at 30 °C. The applied potential to the electrode should be one of the key factors of high selectivity, and the relatively low potential of +0.2 V versus Ag/AgCl was found to be optimal for the detection of sulfite ions. Good sulfite‐ion sensing should be enabled by Cu+ in Sm1.9Ce0.1CuO4 where SO32− is easily adsorbed. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

An efficient electrochemical sensor for determination of sulfite in water and soft drinks based on Ce3+-doped CuO nanocomposite

This study addressed the preparation, characterization, and assay of a screen-printed electrode (SPE) modified with the Ce3+ doped-CuO nanocomposite for the voltammetric detection of sulfite ions. Therefore, the dimension of the new nanocomposite and its morphology were verified by characterization analyses such as energy-dispersive X-ray spectroscopy (EDX), scanning electron microscope (SEM) and X-ray diffraction (XRD). According to cyclic voltammetry (CV), the oxidation of the sulfite at the Ce3+-doped CuO/SPE followed an irreversible and diffusion-controlled mechanism. The results indicated that the new electrode exhibited good electrocatalytic activities towards sulfite oxidation, based on which an electrochemical sensor was presented to detect sulfite. In addition, Ce3+-doped CuO/SPE showed a wide linear range between 0.6 and 400 μM with the limit of detection (LOD) of 0.08 μM to detect sulfite. Finally, this new approach was applied for determining sulfite in real samples, reflecting its utility as one of the cheap analytical tools to control product quality.

P121 Effect of corticosteroids on the host innate immune response and in vitro growth characters during dermatophyte infection.

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PMObjectiveDuring the current epidemic of dermatophytosis, dermatologists in India are noticing atypical clinical presentations of dermatophytosis lesions. Though fixed drug combinations of topical application containing corticosteroid-antifungal-antibacterial drugs are attributed to this phenomenon, it is still not clear about its exact role. Corticosteroids alleviate itching but do not clear off dermatophyte infection from the skin surfaces, which may lead to a relapse of dermatophytosis. Therefore, we analyzed the effect of corticosteroids on host immune response and pathogen in vitro during dermatophyte infection.MethodologyPatients (n = 15) were recruited in three groups; proven cases of dermatophytosis with a history of corticosteroid usage for >30 days (Group A), dermatophytosis with no history of corticosteroid usage for >30 days (Group B), and patients without dermatophytosis and expected to have normal skin (Group C). Skin biopsies were collected and subjected to scanning electron microscopy (SEM) and cytokine expression study. All in vitro experiments were performed with HaCaT Keratinocytes cell line co-cultured with Trichophyton mentagrophytes complex conidia isolated from dermatophytosis (n = 4) and standard strain (n = 1, ATCC 18748). Biopsies were fixed in 2.5% glutaraldehyde and dehydrated through (50%-100%) ethanol gradient. RT-PCR expression of pro-inflammatory cytokines (IL-6, TNF-a, IL-1β, IL-1α, IFN-ϒ, TLR-2, and TLR-4) from skin biopsies and HaCaT cells were conducted using beta-actin as reference gene. The viability and Cell-cycle analysis of HaCaT cells in the presence and absence of clobetasol propionate (0.05% w/w) was performed by MTT assay and Propidium Iodide (PI) staining via flow cytometry, respectively. Growth kinetics of dermatophytes was performed for 96 h in presence and absence of corticosteroid. Expression of sulfite efflux pump gene (ssu1) and pH response gene (pacC), involved in virulence of Trichophyton mentagrophytes complex clinical isolates from classical and atypical lesions (n = 3 each) as well as standard ATCC 18748 was studied by RT-PCR. All results were statistically analyzed using GraphPad Prism 6 software.ResultsSEM results showed skin atrophy in skin biopsies from patients with steroid usage. Relative gene expression (2-Δct) of pro-inflammatory cytokines from skin biopsies was significantly reduced in IL-6, IL-1β, IFN-ϒ, TLR-2 (P-values = .001; .005; .004; .001) in steroid-modified tinea group. Similarly, a difference was observed in keratinocytes in vitro. According to in vitro analysis clobetasol propionate treatment significantly arrests HaCaT cells in the S/G2M phase (P-value = .04). Corticosteroid slows down the growth of dermatophytes in the presence of corticosteroid. A significant upregulation was observed in ssu1 during co-culture of dermatophytes with HaCaT cells as well when co-culture was treated with corticosteroid as compared to the culture alone whereas significant changes were not observed with pacC in similar conditions.ConclusionIncreased atrophy caused by corticosteroids allows dermatophytes to thrive on the intact keratin when steroid pressure is removed. Reduced cytokine response, viability, and S-phase arrest in host correlate with delayed clearance of dermatophyte infection from skin. Delayed growth of dermatophytes in the presence of corticosteroids and upregulation of ssu1 in dermatophytes when co-cultured with keratinocytes and corticosteroid correlates with recurrent infection. In addition, increased production of sulfite ions that degrade keratin may lead to the formation of widespread lesions.

Changes in Sulfur Metabolism in Mouse Brains following Radon Inhalation.

Therapy using hot springs, including the high-level radioactive gas “radon”, is traditionally conducted as an alternative treatment for various diseases. Oxidative-stress-related diseases are inhibited by the enhancement of antioxidative functions following radon inhalation. We have reported that radon inhalation increased the level of anti-oxidants, such as glutathione (G-SH), in the brain and had a protective antioxidative effect against transient global cerebral ischemic injury. However, no studies have yet revealed the changes in G-SH associated substances after radon inhalation. In this study, we comprehensively analyzed several metabolites, focusing on G-SH. Mice were exposed to radon at concentrations of 200, 2000, or 20,000 Bq/m3 for 1, 3, or 10 days. We detected 27 metabolites in the mouse brains. The result showed that the L-methionine levels increased, whereas the levels of urea, glutathione, and sulfite ion decreased under any condition. Although the ratio of G-SH to oxidized glutathione (GS-SG) decreased, glutathione monosulfide (G-S-SH) and cysteine monosulfide (Cys-S-SH) increased after radon inhalation. G-S-SH and Cys-S-SH can produce a biological defense against the imbalance of the redox state at very low-dose irradiation following radon inhalation because they are strong scavengers of reactive oxygen species. Additionally, we performed an overall assessment of high-dimensional data and showed some specific characteristics. We showed the changes in metabolites after radon inhalation using partial least squares-discriminant analysis and self-organizing maps. The results showed the health effects of radon, especially the state of sulfur-related metabolites in mouse brains under the exposure conditions for radon therapy.

Highly Sensitive and Selective Sulfite Ion Sensor Based on Biochemically Stable Iodo‐Functionalized Coumarin Fluorophores

AbstractBelonging to the class of sulfur oxyanions, the physiologically prevalent sulfite (SO32−) species has been serving as a popular synthetic additive to enhance the shelf life of a plethora of foods and beverages like bread and wine. On the contrary, an impermissible endogenous accumulation of this reactive sulfur species via multiple factors has been concerned in the functioning of skin disorders and neurodegenerative diseases like Alzheimer's. Accordingly, a pivotal role of sulfite in food quality and human health warrants a reliable analytical technique for the rapid and sensitive detection of SO32− ions in environmental specimens. This article features a new‐fangled iodo‐functionalized coumarin molecule (D), followed by an exploration of its analytical utility as a selectively sensitive sensor for SO32− ions via “switch‐on” fluorescence. In stark contrast to its poorly ion‐discriminating iodine‐free analogue (E) as reported in the literature, the new fluorophore D was capable of rapidly sniffing out sulfite ions (∼3 min) in a specific range of 1000–1 μM, in the back‐drop of a diverse array of environmentally relevant anions at an ultra‐low concentration of 77 nM in semi‐aqueous medium by using simple and cheap fluorescence spectroscopy. The formed sensor found highly selective and sensitive in presence of wide variety of interfering ions and biothiols, which suggest their extreme utilization in the real samples. According to best of our knowledge, it is the first report, which can detection sulfite ion at very low concentration level and it work efficiently under UV‐illumination with bright fluorescence. A comparable sensitivity of D towards the target analyte (SO32− ions) was also recorded in real samples i. e. fresh real water samples and fresh juice specimens.

Recyclable flexible upconversion-luminescence sensing platform for quantifying sulfite based on inner filter effect

The widespread applications of sulfur dioxide and its derivatives is a double-edged sword in terms of ensuring environmental and food safety. In this work, a recyclable flexible upconversion-luminescence sensor was developed for the determination of sulfite in environmental and foodstuff samples. The upconversion nanoparticles (UCNPs) were uniformly doped with polydimethylsiloxane (PDMS) prepolymer and moulded to prepare a flexible upconversion-luminescence substrate, which was further modified with pararosaniline (PRA) dye based on the typical carbodiimide coupling procedure. The principle of the work was based on the inner filter effect (IFE) mechanism between PRA dye and UCNPs. In the presence of target sulfite ions, it selectively binds to PRA moieties fixed on the surface of the flexible sensor, resulting in its bleaching and restoration of the upconversion fluorescence. Under the optimized conditions, a linear response for sulfite concentration in the range of 10–100 nM was obtained. The limit of detection was calculated as 2.24 nM, and the proposed sensor was successfully regenerated and recycled six times. The method was applied in real rainwater samples with spiked recoveries in the range of 94.85%–99.39%, and the coefficient of variation ranged from 1.65% to 4.93%. Hence, the proposed flexible upconversion-luminescence sensor held the attractive potential for efficient sulfite determination in real environmental and food samples.

Sulphur and particulate matter affecting on soil and underground plants

Environmental problems were faced, and one of them is the accumulation of Sulphur and its compounds in the atmosphere and through the atmosphere, it accumulates in the soil and then the underground plants. In the atmosphere Sulphur it is present in the form of aerosols and acid precipitation. Volatile Sulphur compounds are released by the combustion of fossil fuels and volcanic eruption also produces Sulphur oxides. Deficiency of Sulphur produces paling of plants and denaturing of some enzymes that are then fulfilled by using the fertilizers of Sulphur. Soil also has an adverse effect when particulate matter or Sulphur aggregates in the plants and their physiological and biological development is retarded. Most of the industrial processes contain Sulphur compounds like thiol, thiophene, oxides of Sulphur etc. Structural and chemical mutation occurs when particulate substances induce into the plants and productivity and efficiency of that plant is reduced. The impact of acid rain in places with high quantities of mixed air pollutants has yet to be determined. Acid inputs appear to be affecting several techniques in field soils. These must be measured in terms of plant output. SO2 enters the leaves via stomata and quickly dissolves in Apoplastic water, producing mostly Sulphite (SO3)-2, bisulphite (HSO-3), and H+ ions. SO2 phytotoxicity has been attributed to Sulphite and bisulphite ion interactions with different chemicals. If the quantities are not too high, most leaves can detoxify Sulphite and bisulphite by oxidizing them to less harmful Sulphate ions via a series of processes. SO2 absorbed by foliage may undergo reduction conversion, including absorption into organic Sulphur compounds and release from the leaves as H2S. The oxidizing or reducing route of SO2 in plants is determined by plant species, soil Sulphur content, SO2 amount and persistence, and plant growth conditions.

Crystal structures of YeiE from Cronobacter sakazakii and the role of sulfite tolerance in gram-negative bacteria

SignificanceYeiE has been identified as a master virulence factor of Cronobacter sakazakii. In this study, we determined the crystal structures of the regulatory domain of YeiE in complex with its physiological ligand sulfite ion (SO32-). The structure provides the basis for the molecular mechanisms for sulfite sensing and the ligand-dependent conformational changes of the regulatory domain. The genes under the control of YeiE in response to sulfite were investigated to reveal the functional roles of YeiE in the sulfite tolerance of the bacteria. We propose the molecular mechanism underlying the ability of gram-negative pathogens to defend against the innate immune response involving sulfite, thus providing a strategy to control the pathogenesis of bacteria.

Spectrophotometric determination of sulphite and thiamin hydrochloride via Xylenol orange dye

a simple, acurate and rapid spectrophotometric method for determination of sulphite and thiamine hydrochloride (B1) is described. This method used proton transfer reaction between sulphite ion with xylenol orange at pH(7.6) to develop red colour adduct that of maximum absorption at 580 nm. This adduct was used for determination of thiamine hydrochloride by bleaching the red colour product (xylenol orange-sulphite) at the optimum conditions established for the determination of sulphite. Beer’s law is obeyed in the concentration range (10-1000) μg/25ml (i.e. 0.4-40) of sulphite and 10-2000, μg/25ml (i.e. 0.4-80) for thiamine hydrochloride at the selected wavelength, the molar absorbtivity 2.8×104 l.mol-1.cm-1 for SO32- and 2.69×104 l.mol-1.cm-1 for thiamine hydrochloride, Sandell's index for sensitivity 0.002857 μg .cm-2 for sulphite and 0.012537 μg .cm-2 for B1. Good recoveries of sulphite and thiamine hydrochloride from water samples and pharmaceutical formations are achieved using the proposed method.

Monolayer assembly of gold nanodots on polyelectrolyte support: A multifunctional electrocatalyst for reduction of oxygen and oxidation of sulfite and nitrite

AbstractThe present work demonstrates a monolayer self‐assembly of methionine‐capped gold nanodots (AuNDs) on the glassy carbon electrode (GCE) and its application in various electrocatalytic reactions. Positively charged poly(acrylamide‐co‐diallyldimethylammonium chloride) (PADA)‐modified GCE was used as electrode substrate and monolayer assembly of negatively charged AuNDs was performed over PADA‐modified GCE by simple dipping method. The successful modification of AuNDs on GCE was confirmed by characteristic cyclic voltammetry behavior of gold oxidation and reduction. Further to optimize the dipping time duration of AuNDs self‐assembly, dipping time‐dependent electrocatalysis was performed. Interestingly, the prepared AuNDs self‐assembled electrodes exhibit very good electrocatalytic activity in the reduction of oxygen with excellent methanol tolerance and simultaneous electrooxidation of pollutants and food additives, nitrite, and sulfite ions.

A multi-site probe for selective detection of cyanide and sulphite ions via different mechanisms with concomitant different fluorescent behaviors

A novel organic probe (R) possessing multiple binding sites has rationally been designed, synthesized and characterized using NMR and mass spectral techniques. The probe R displays an excellent selective and sensitive response to CN– and SO32– ions over other anions. In aq. DMSO solution, R exhibits dual emission (463 and 590 nm) upon interaction with CN– ion, which is ascribed to the deprotonation of the NH group of the probe. Upon addition of SO32– ion, the enhancement of fluorescence for R at 478 nm is attributed to the formation of 1:1 adduct between R and SO32– ion by the nucleophilic addition of SO32– to C-atom of the ring CCH moiety. The fluorescence responses of R toward CN– and SO32– ions are pH independent in the 5 – 9 range. Limits of detection down to 28 and 3.7 nM were determined for CN– and SO32– quantitation, respectively. Theoretical calculations (DFT and TDDFT) are applied to interpret the absorption and dissimilar emission behaviour of the probe and its adduct with CN– and SO32– ions. The CN– induced dual fluorescence in R may be due to relaxation of the excited state to two different ground states.

ТЕСТ-РОССЫПИ НА ОСНОВЕ МОДИФИЦИРОВАННОЙ КОСТРЫ КОНОПЛИ ДЛЯ ЭКСПРЕССНОГО ОПРЕДЕЛЕНИЯ ПОДВИЖНЫХ ФОРМ ФОСФОРА И СУЛЬФИТОВ В ПОЧВАХ И ВОДНЫХ ПРОБАХ

The methods of manufacturing test placers and compositions for visual-blister colorimetric determination of concentrations of phosphate ions and sulfi te ions for their quantitative determination in soils and water bodies have been optimized. The test placer contains all the reagents for the analytical reaction. Placers allow the quantitative determination of phosphates and sulfi des in aqueous samples without prior preparation of reagent solutions. In a blister cell with a diameter of 6 mm, a much more intense color was achieved with a solution layer of no more than 2 mm. The application of reagents to the surface of homogenized and discolored hemp awns avoids their contact until the chemical analytical reaction takes place. The composition of placers and the conditions for applying reagents are optimized. Suffi ciently high acidity can be provided by hydrosulfate ions with the addition of a few drops of solution. The reaction proceeds in the volume of the added test solution, which is 2-3 drops.

Dynamic Control of Photocatalytic Proton Reduction through the Mechanical Actuation of a Hydrogel Host Matrix.

This paper describes a photocatalytic hydrogen evolution system that is dynamically and reversibly responsive to the pH of the surrounding solution through the actuation of a microhydrogel (microgel) matrix that hosts the photocatalysts (CdSe/CdS nanorods). The reversible actuation occurs within 0.58 (swelling) and 1.7 s (contraction). ΔpH = 0.01 relative to the pKa of the tertiary amine on the microgel polymer (7.27) results in a reversible change in the average diameter of the microgel hosts by a factor of 2.4 and a change in the photocatalytic turnover frequency (TOF) by a factor of 5. Kinetic isotope effect and photoluminescence quenching experiments reveal that the scavenging of the photoexcited hole by sulfite ions is the rate-limiting step and leads to the observed response of the TOF to pH through the actuation of the microgel. Molecular dynamics simulations quantify a greater local concentration of sulfite hole scavengers for pH < pKa.

A cleaner application on hydrogen sulfide

With the increasing industrial production, there was a significant number of toxic and harmful hydrogen sulfide (H2S) gas generated. Due to the industrial activities, converting H2S gas from the waste of industrial process is environmentally attractive. This paper focuses on the conversion of H2S to elemental sulfur (S°) and other sulfur species (i.e., sulfite ion (SO32-); sulfate ion (SO42-) using Fenton reagent. The effects of some reaction parameters such as Fe2+ ion concentration, amount of hydrogen peroxide (H2O2), reaction time, initial H2S concentration and, liquid-gas ratio on H2S conversion percentage were explored thoroughly. The results revealed that the increase of the Fe2+ ion concentration and H2O2 quantity could promote the conversion of H2S. Besides, the comparable results were recorded for each reaction parameter. An apparent positive effect was observed with increasing the amount of H2O2 on H2S conversion. However, the conversion percentage was decreased while increased in the initial concentration of the H2S in the Fenton reactor. It was well accepted that the main conversion pathway of H2S was hydroxyl radical (•OH). Additionally, the oxidative reaction of H2O2 on H2S is thought another removal pathway. The expected products are sulphuric acid and S°.

Sulfur(IV) assisted oxidative removal of organic pollutants from source water

The removal of organic pollutants presents a major challenge for drinking water treatment plants. The chemical oxygen demand (COD) is essentially the measure of oxidizable organic matter in source waters. In this study, we report that COD can efficiently be decreased by adding Fe(II)/Fe(III) and sulfite ion to the source water while purging it with air. In this process, oxygen is activated to oxidize the main constituents of COD, i.e. organic substrates, via the generation of reactive inorganic oxysulfur radical ions. In the end, the total amount of sulfur(IV) is converted to the non-toxic sulfate ion. It has been explored how the COD removal efficiency depends on the concentration of S(IV), the total concentration of iron species, the concentration ratio of Fe(II) and Fe(III), the purging rate and the contact time by using source water from a specific location (Királyhegyes, Hungary). The process has been optimized by applying the Response Surface Methodology (RSM). Under optimum conditions, the predicted and experimentally found COD removal efficiencies are in excellent agreement: 85.4% and 87.5%, respectively. The robustness of the process was tested by varying the optimum values of the parameters by ± 20%. It was demonstrated that the method is universally applicable because a remarkable decrease was achieved in COD, 62.0–88.5%, with source waters of various compositions acquired from 9 wells at other locations using the same conditions as in the case of Királyhegyes.

A combination of experimental and TD-DFT investigations on the fluorescent detection of sulfite and bisulfite ions in aqueous solution via nucleophilic addition reaction

The selective detection of sulfite and bisulfite ions with anthracene-based compounds (CN1 and CN2) as chemo-dosimeters is reported using fluorescence changes in DMSO:HEPES (70:30%), v/v buffer solution (pH 7.4). Upon treatment with sulfite and bisulfite ions, the fluorescence of the probes gets enhanced significantly at 424 nm. The detection of these ions occurs through the nucleophilic addition at the vinylic C-atom of the probes, which terminates the photo-induced electron transfer (PET) process and consequently enhances the fluorescence. This detection mechanism is well supported by 1H NMR titration, HR-MS and DFT/TD-DFT calculations. The pseudo-first-order rate constants for the addition sulfite (at pH 7.4) and bisulfite (at pH 5) to CN1 are determined to be 3.22×10−3 and 5.02×10−3 s−1, respectively. The limits of detection for sulfite and bisulfite are found to be 1.85×10−7 and 1.56×10−7 M, respectively. The probe CN1 was successfully applied to the detection of bisulfite ion in real samples.