Search Results (61)

In the context of chlorate’s application as a cathodic reagent of power sources, the mechanism of its electroreduction has been studied in electrochemical cells under diffusion-limited current conditions with operando spectrophotometric analysis. Prior to electrolysis, the electrolyte is represented as an aqueous mixed NaClO₃ + H₂SO₄ solution (both components being non-electroactive within the potential range under study), without addition of any external electroactive catalyst. In the course of potentiostatic electrolysis, both the cathodic current and the ClO₂ concentration demonstrate a temporal evolution clearly pointing to an autocatalytic mechanism of the process (regions of quasi-exponential growth and of rapid diminution, separated by a narrow maximum). It has been substantiated that its kinetic mechanism includes only one electrochemical step (chlorine dioxide reduction), coupled with two chemical steps inside the solution phase: comproportionation of chlorate anion and chlorous acid, as well as chlorous acid disproportionation via two parallel routes. The corresponding set of kinetic equations for the concentrations of Cl-containing solute components (ClO₃⁻, ClO₂, HClO₂, and Cl⁻) has been solved numerically in a dimensionless form. Optimal values of the kinetic parameters have been determined via a fitting procedure with the use of non-stationary experimental data for the ClO₂ concentration and for the current, taking into account the available information from the literature on the parameters of the chlorous acid disproportionation process. Predictions of the proposed kinetic mechanism agree quantitatively with these experimental data for both quantities within the whole time range, including the three characteristic regions: rapid increase, vicinity of the maximum, and rapid decrease. Full article

This study evaluated the inhibitory efficacy of sulphur dioxide, hydrogen peroxide, copper sulphate pentahydrate, chlorine-based formulations, a chlorine-free formulation, ethanol, and acetic acid against Cladosporium cladosporioides, Aspergillus niger, and Penicillium expansum. An in vitro inhibition test was employed to investigate the inhibitory properties. The results demonstrated different sensitivities of filamentous fungi to the inhibitors. All tested substances displayed fungicidal properties. Sulphur dioxide (40% NH₄HSO₃ solution) inhibited growth at a 4% v/v concentration. No minimum effective concentration was established for H₂O₂; only a 30% w/v solution inhibited P. expansum. CuSO₄·5H₂O completely inhibited fungal growth at 5% w/v solution, with 2.5% w/v also proving effective. For the chlorine-based product, 40% w/v solution (48 g∙L⁻¹ active chlorine) had the most substantial effect, though it only slowed growth, and NaClO solution completely inhibited growth at 2.35 g NaClO per 100 g of product (50% w/v solution). FungiSAN demonstrated fungicidal effects; however, the recommended dose was insufficient for complete inhibition. Ethanol exhibited the lowest efficacy, while the inhibitory threshold for CH₃COOH was found to be a 5% v/v solution. The findings of this study may serve as a basis for informed decision-making when selecting the most suitable product, depending on specific application conditions. Full article

Chlorine dioxide (ClO₂) is a powerful sterilizing agent that is widely used to prevent the spoilage of fresh foods during delivery and storage. However, its practical applications are hindered by a short sterilization duration, complex deployment processes, and high treatment costs. To address these challenges, an innovative ClO₂ self-releasing sachet was developed, which was specifically designed for use in retail and wholesale markets. The sachet utilizes polyether block amide (PEBAX^®) as a hydrophilic polymer to facilitate the dissociation of sodium chlorite (NaClO₂) and citric acid (CA), which generates ClO₂. A PEBAX/CA composite film was coated onto kraft paper to construct the sachet. This design extended the ClO₂ release period to over 3 d, with a controllable release rate being achieved by adjusting the concentrations of NaClO₂ and CA. In practical tests, the sachets inhibited fungal growth by >50% over 14 d at 20 °C within a corrugated box. Furthermore, they preserved the quality of the cherry tomatoes for 16 d during storage. These results demonstrate that the newly developed sachet offers an economical and user-friendly solution for fresh-food packaging, effectively preserving product quality. Full article

Organosulfur compounds are appealing owing to the diverse oxidation states accessible by sulfur, allowing the precise adjustment of their properties. In this study, we report a practical oxidation method that converts sulfides to sulfones by generating chlorine dioxide in situ from sodium chlorite (NaClO₂) and hydrochloric acid (HCl) in organic solvents. Diphenyl sulfide was effectively oxidized to diphenyl sulfone in yields of up to 96% under optimized conditions, with high selectivity in ethyl acetate and acetonitrile solvents. The method is compatible with a wide range of substrates, including various aryl, benzyl, and alkyl sulfides, although reactivity diminishes with sterically hindered or electron-rich substrates. This scalable and environmentally friendly process overcomes challenges associated with aqueous oxidants, such as substrate solubility and side reactions, providing a robust alternative for sulfone synthesis. Full article

This article deals with the removal of manganese from water via ultrafiltration and the oxidation of manganese with chlorine dioxide or potassium permanganate before ultrafiltration. The dose of oxidizing agents, time of contact with water, and manganese concentration in raw and treated water were monitored. A fully automated ultrafiltration device with membrane module UA-640 (Microdyn-Nadir) was used. A tubular reactor with a static mixer was used to reach a sufficient contact time for water with an oxidizing agent, enabling the oxidation of manganese in water. The concentration of Mn in the water source ranged from 0.150 to 0.250 mg/L Mn. The results of the experiments showed that in the case of chlorine dioxide, the efficiency of removing Mn from water of 74.31% was achieved at a flow rate of 60 L/h, a dose of 0.4 mg/L ClO₂ and a retention time of 30.5 min; the concentration of Mn in the treated water was 0.037 mg/L, while in the case of KMnO₄ the efficiency was up to 100% at a flow rate of 650 L/h, a dose of 0.3 mg/L Mn (determined after adding KMnO₄) and a retention time of 2.8 min; the concentration of Mn in the treated water was below the detection limit of 0.005 mg/L of the measuring device. Pilot plant experiments confirmed the efficiency of ultrafiltration, demonstrating the possibility of decreasing the manganese concentration below the limit for drinking water using the considered method. Full article

Gaseous chlorine dioxide (ClO₂) is a potent antimicrobial agent used to control microbial contamination in food and water. This study evaluates the bactericidal activity of gaseous ClO₂ released from a sodium chlorite (NaClO₂) pad against Campylobacter jejuni. Exposure to a low concentration (0.4 mg/L) of dissolved ClO₂ for 2 h resulted in a >93% reduction of C. jejuni, highlighting the bacterium’s extreme sensitivity to gaseous ClO₂. To elucidate the molecular mechanism of ClO₂-induced bactericidal action, transcriptomic analysis was conducted using RNA sequencing (RNA-seq). The results indicate that C. jejuni responds to ClO₂-induced oxidative stress by upregulating genes involved in reactive oxygen species (ROS) detoxification (sodB, ahpC, katA, msrP, and trxB), iron transport (ceuBCD, cfbpABC, and chuBCD), phosphate transport (pstSCAB), and DNA repair (rdgB and mutY). Reverse transcription-quantitative PCR (RT-qPCR) validated the increased expression of oxidative stress response genes but not general stress response genes (spoT, dnaK, and groES). These findings provide insights into the antimicrobial mechanism of ClO₂, demonstrating that oxidative damage to essential cellular components results in bacterial cell death. Full article

Ilmenite concentrate has emerged as the key titanium raw material for exploitation and utilization, playing a crucial role in the preparation of metallic titanium and titanium dioxide. However, the presence of impurities such as Fe, Ca, and Mg in ilmenite concentrate severely restricts its economic utilization and environmentally friendly applications. In our previous research, a novel process was proposed to prepare TiCl₄ from high-Ca- and Mg-containing ilmenite through carbothermal reduction and boiling chlorination. Nevertheless, the employment of graphite as a reducing agent and hydrochloric acid for metallic iron separation led to elevated production costs. The aim of this study was to explore an alternative and more cost-effective method. Petroleum-derived coke was used as the reducing agent to investigate the feasibility of producing titanium oxycarbide from ilmenite concentrate via carbothermal reduction and magnetic separation. The results showed that petroleum-derived coke is capable of reducing ilmenite concentrate to coral-shaped TiC_xO_y under high-temperature conditions. However, an approximate 100 °C increment in temperature is required to reach an equivalent reduction efficiency compared with graphite. The X-ray diffraction (XRD) analysis results of the reduced products reveal that complete reduction of ilmenite concentrate by petroleum-derived coke can only be achieved when the reduction process is conducted at 1600 °C for 3 h or at 1500 °C for 5 h. The reduced product obtained at 1600 °C, characterized by a substantial presence of dense Ti₂O₃, exhibits a significantly coarser particle size after 30 minutes of ball milling in contrast to the reduced product obtained at 1200 °C, which is rich in M₃O₅ anosovite. Magnetic separation results showed that the reduction product at 1200 °C could not have metallic iron removed by magnetic separation at 1.2 T, while the reduction product at 1600 °C could yield a non-magnetic charge rich in Ti₂O₃ and TiC_xO_y with an iron content as low as 2 ± 0.03 wt.%, which fully meets the requirements for producing TiCl₄ by boiling chlorination. Overall, these research results offer a new approach for the low-cost production of TiCl₄ from ilmenite concentrate with high levels of Ca and Mg impurities through boiling chlorination. Full article

Chlorine dioxide (ClO₂) gas has attracted considerable attention due to its safety and efficiency. In this study, we successfully developed a color-variable ClO₂ slow-releasing card for postharvest litchi. The optimal ClO₂ slow-releasing card was prepared as follows: Card A was soaked in 2.5 mol/L NaClO₂ and 0.3 mol/L CaCl₂. Card B was soaked in 1 mol/L oxalic acid, 0.3 mol/L CaCl₂, and natural pigment. Finally, cards A and B were dried and adhered using 60% gelatin. The ClO₂ releasing time of the card was more than 120 h at 5–25 °C, and it could change color from dark yellow to white. The qualities of 3 kg litchi treated with no pieces (CK), half a piece (T1), one piece (T2), two pieces (T3), and three pieces (T4) of ClO₂ slow-releasing card were compared. The results showed that litchi of T1 had significantly (p < 0.05) higher L* and a* values but a lower respiration rate and relative conductivity than CK after 7 days of storage, showing the best pulp qualities and pericarp color. Further correlation analyses revealed a significant positive correlation (R² = 0.971) between Cya-3-O-gal-1 and a*, indicating a sharp decline in Cya-3-O-gal-1 and strong pericarp browning in CK. On the contrary, the low-releasing ClO₂ of T1 effectively inhibited Cya-3-O-gal-1 degradation. This could be one of the reasons for the superior pericarp color of T1. This study provides a visual, efficient, and economical solution for postharvest litchi. Full article

Recently, the activation of chlorine dioxide (ClO₂) by metal(oxide) for soil remediation has gained notable attention. However, the related activation mechanisms are still not clear. Herein, the variation of iron species and ClO₂, the generated reactive oxygen species, and the toxicity of the degradation intermediates were explored and evaluated with nanoscale zero-valent iron (nFe⁰) being employed to activate ClO₂ for soil polycyclic aromatic hydrocarbon (PAH) removal. With an optimized ClO₂/nFe⁰ molar ratio of 15:1 and a soil/water ratio of 3:1, the degradation efficiency of phenanthrene improved 12% in comparison with that of a ClO₂-alone system. The presence of nFe⁰ significantly promoted ClO₂ consumption (improved 85.4%) but restrained ClO₂⁻ generation (reduced 22.5%). The surface Fe(II) and soluble Fe(II) in the ClO₂/nFe⁰ system was 2.0-fold and 2.8-fold that in the nFe⁰ system after 2 min. Electron paramagnetic resonance analysis, along with quenching experiments, revealed that Fe(IV), HOCl, and •OH dominated phenanthrene degradation in a ClO₂/nFe⁰ system, with oxidation contributions, respectively, of 34.3%, 52.8% and 12.9%. The degradation intermediates of PAHs in the ClO₂/nFe⁰ system had lower estimated toxicity than those of the ClO₂ system. The lettuces grown in ClO₂/nFe⁰-treated soil displayed better results in bioassay indexes than those grown in ClO₂-treated soil. This study offers new perspectives for the remediation of organic-pollutant-contaminated soil by using metal-activated ClO₂ technology. Full article

Pharmaceutical preclinical tests using cell cultures are nowadays commonly automated. Incubator microbial contaminations impact such tests. Chlorine dioxide (ClO₂) is widely used in aqueous solutions. However, a gaseous form, such as chlorine dioxide gas (gClO₂), can effectively access unreachable spaces, such as closed cell culture incubators. Steam sterilization requires a temperature rise to at least 121 °C, thus limiting the possibility of automation elements for sensors and actuators. gClO₂ sterilization is an ambient-temperature sterilization method. This article aims to demonstrate that gClO₂ generated from solid powder tablets is efficient for sterilizing incubators and can be automated. We selected (i) Bacillus subtilis strain, (ii) Saccharomyces cerevisiae, and (iii) T7 phages as representatives for (i) bacteria, (ii) fungi, and (iii) viruses for each domain to evaluate the sterilization efficiency. This study demonstrated that gClO₂ can be generated inside the incubator from a solid powder tablet without specific equipment and can effectively fight biological proxies in 15 min. After 30 sterilization cycles, the actuators and sensors mounted inside the incubator were still operating. Our proposed sterilization method seems to be generally applicable for automated in situ sterilization of incubators and medical robots. Full article

The application of chlorine dioxide (ClO₂) in microbial safety and quality maintenance of fresh produce has received extensive attention. Fresh-cut button mushrooms (Agaricus bisporus) are prone to spoilage, resulting in a short shelf-life. In this study, ClO₂ treatment was used to preserve fresh-cut button mushrooms, and its effect on maintaining the postharvest quality was investigated using sensory evaluation, weight loss, color, firmness, respiration rate, electronic-nose (E-nose) analysis and microbial analysis. During the 8 d storage, both the 50 and 100 mg·L⁻¹ ClO₂ treatment reduced the aerobic bacteria count on the surface of fresh-cut button mushrooms. However, the results showed that the 50 mg·L⁻¹ ClO₂ treatment but not the 100 mg·L⁻¹ ClO₂ treatment significantly inhibited the deterioration of comprehensive quality. The 50 mg·L⁻¹ ClO₂ treatment maintained the high sensory evaluation and pleasant volatile odor of fresh-cut button mushrooms as well as reduced the decreasing of fresh weight and firmness. Contrary to expectations, the application of ClO₂ treatment showed worse appearances in color (lower L^*, higher a^*, b^* and browning index) of fresh-cut button mushrooms. Significant differences were observed between CK and ClO₂-treated groups from day 0 to day 6, while there were no significant differences of a^*, b^* and browning index between CK and the 50 mg·L⁻¹ ClO₂ treatment at the end of storage (on day 8). In conclusion, the 50 mg·L⁻¹ ClO₂ can maintain the good quality of fresh-cut button mushrooms. Full article

Microbial contamination during seafood processing can often lead to a reduction in shelf life and the possibility of food-borne illnesses. Sanitisation with chlorine-based products during seafood processing is therefore sometimes undertaken. This study compared the effects of two sanitisers, chlorine dioxide (ClO₂) and hypochlorous acid (HOCl) at their suggested concentration (5 ppm and 10 ppm; 50 ppm and 100 ppm respectively), on physical, chemical, and microbial qualities of Atlantic salmon (Salmo salar) fillets throughout 7 days of simulated retail display refrigeration. Parameters used for assessment included quality index (QI), drip loss, colour, texture, histology, total volatile base nitrogen (TVB-N), lipid oxidation (malonaldehyde, MDA), pH, and total viable count changes. Results indicated that whilst drip loss increased over the storage time, day 4 and 7 drip loss in both sanitisers decreased significantly compared with the control. There was a linear relationship (R > 0.70) between QI and storage time in all treatments, particularly in regard to skin brightness, flesh odour, and gaping parameters, but treatment differences were not present. Texture parameters including gumminess, chewiness, and hardness increased over time in the control whilst both sanitiser treatments seemed to provide protective effects against texture hardening during storage. The observed softening effects from the sanitiser treatments were aligned with microstructural and cytological changes in the histology results, as evidenced by a reduced fibre–fibre adhesion, myodigeneration, and an increase in interfibrillar space over storage time. Colour, especially chroma (C*), was shown to decrease over time in control, whereas insignificant protective effects were observed in both sanitiser treatments at day 7. Irrespective of treatment and storage time, MDA levels exceeded the acceptable limit on all days, whilst TVB-N levels were below the critical limit. Although pH was influenced by treatment and storage time, the pH was within the normal range. Microbiological results showed that with sanitiser addition, TVC was below the permissible level (10⁶ CFU/g) until day 4 but ClO₂ ice (5 ppm), ClO₂ (10 ppm), and HOCl (100 ppm) treated fillets all exceeded the limit on day 7. The mixed results on the effect of sanitiser addition on fillet quality and shelf life suggested that further investigation on pathogen reduction, sanitiser introductory method, as well as testing the same treatments in low-fat fish models would be recommended. Full article

Tomato brown rugose fruit virus (ToBRFV), being a mechanically transmitted disease, is usually difficult to control; therefore, an effective alternative to reduce transmission and replication in the crop is by spraying with chlorine dioxide (ClO₂) during routine crop management. In this research, the efficacy of chlorine dioxide (ClO₂) for ToBRFV management in a greenhouse and open field was determined. The phytotoxicity of ClO₂ and its effective concentration against ToBRFV in Nicotiana longiflora plants were evaluated. Subsequently, the effect of ClO₂ on ToBRFV was evaluated in tomato plants grown in an open field. Finally, the effectiveness of ClO₂ on plants inoculated with ToBRFV under greenhouse conditions was evaluated and the number of necrotic local lesions (NLLs) was quantified. The results revealed that ClO₂ at 760 mg L⁻¹ did not show phytotoxicity and reduced the number of NLLs in N. longiflora plants. It also decreased ToBRFV transmission and replication in field- and greenhouse-grown tomato plants, improving agronomic parameters. ClO₂ reduced replication in plants inoculated with different amounts of ToBRFV inoculum in a greenhouse. N. longiflora leaves expressed lower numbers of NLLs when inoculated with ClO₂-treated tomato plant extracts. Finally, the results demonstrate that ClO₂ represents an effective management alternative when used by direct application to plants. To our knowledge, this is the first study where the use of an antiviral compound is carried out under field and greenhouse conditions. Full article

Cherimoya (Annona squamosa L.) is a nutrient-rich fruit. However, it is not easy to store because of its susceptibility to browning. In order to prolong the storage period of cherimoya, the fruit was treated with chlorine dioxide (ClO₂) at different concentrations (20, 40, 60, 80, and 100 mg L⁻¹) and stored at 15 °C for 8 days. The quality and biochemical indexes of the fruit were investigated using a chromameter, high-performance liquid chromatography and scanning electron microscopy, etc. The results showed that all the treatments with various concentrations of ClO₂ could delay the increase in the browning index, loss of weight, and decrease in hardness. Meanwhile, ClO₂ treatment effectively reduced the consumption of starch, titratable acids, and phenolics as well as inhibited the polyphenol oxidase (PPO) activity and enzymatic oxidation. It can be seen from the Fourier transform infrared spectrum (FTIR) that the C=O stretching peak at 1731 cm⁻¹ disappeared at a ClO₂ concentration of 60 mg L⁻¹. We think the ClO₂ treatment may inhibit the oxidation of phenol to quinone. According to the Arrhenius formula, the values of the apparent activation energy (E_a) for enzymatic browning reaction were estimated. The E_a with catechol in cherimoya pericarp and flesh were 67.00 and 47.83 kJ mol⁻¹, respectively. It was found that the phenolic enzyme reaction with catechol has a much smaller E_a and a higher affinity for PPO. Therefore, treatment with ClO₂ at a suitable concentration for cherimoya stored at 15 °C could effectively maintain fruit quality and prolong the storage period; the most appropriate concentration is 60 mg L⁻¹. Full article

The chlorination of oxides of major concern in cassiterite concentrate with various chlorinating agents is investigated in light of their thermodynamic feasibilities to extract and recover their valuable metal components. Mechanisms responsible for the processes and their Gibbs free energy changes as a function of temperature to selectively separate and/or recover the metal(s) of interest and unwanted ones as their metallic chlorides are identified. Attention is given to gaseous (Cl₂ and Cl₂ + CO mixture) and solid (CaCl₂ and MgCl₂) chlorine sources, from which Cl₂ + CO shows no reaction selectivity for any of the oxides but a feasible metal chloride formation for all. Chlorine gas (Cl₂), on the other hand, could selectively form chlorides with metals of +2 oxidation state in their oxides, leaving those of high oxidation state unreacted. MgCl₂, unlike CaCl₂, is found capable of producing calcium, ferrous, and stannic chloride from their metallic oxides with enhanced reaction tendencies in the presence of silicon dioxide (SiO₂). An overall study of the thermodynamic feasibility of all chlorine sources looked at alongside operational and environmental viabilities suitably suggests MgCl₂ for a selective extraction of the valuable metal components in a cassiterite concentrate, in which case, moderate temperatures seem promising. Full article