Showing papers on "Sodium chlorate published in 2022"

Full and Sustainable Electrochemical Production of Chlorine Dioxide

Abstract: With the final purpose of manufacturing electrochemically-based devices that produce chloride dioxide efficiently, this paper focuses on the production of chlorates and hydrogen peroxide in two different electrochemical cells, in which operation conditions are selected to obtain high efficiencies, and in the subsequent combination of both electrochemically manufactured solutions to produce chlorine dioxide. Results demonstrate that suitable reagents can be produced by electrolyzing 20 g L−1 sodium chloride solutions at 50 mA cm−2 and 50 °C, and 3000 mg L−1 NaClO4 solutions at 5.0 mA cm−2 and 15 °C with current efficiencies of 30.9% and 48.0%, respectively. Different tests performed with these electrolyzed solutions, and also with commercial hydrogen peroxide and chlorate solutions, demonstrate that the ratio between both reagents plays a very important role in the efficiency in the production of chlorine dioxide. Results clearly showed that, surplus chlorate should be contained in the reagent media to prevent further reduction of chlorine dioxide by hydrogen peroxide and consequently, loses of efficiency in the process. During the reaction, a gas with a high oxidation capacity and consisting mainly in chloride dioxide is produced. The results contributed to the maximum conversion reached being 89.65% using electrolyzed solutions as precursors of ClO2, confirming that this technology can be promising to manufacture portable ClO2 devices.

Towards the production of chlorine dioxide from electrochemically in‐situ produced solutions of chlorate

Abstract: BACKGROUND This work focuses on the electrochemical production of chlorate solutions for direct use and integration in the manufacture of chlorine dioxide (ClO2), from the perspective of manufacturing portable ClO2 electrochemical generators. RESULTS Chlorate production was evaluated from the oxidation of sodium chloride (NaCl) contained in brackish solutions (20 g L−1) and brines (200 g L−1) in single chamber flow electrochemical cells. Efficiency in chlorate ion (ClO3−) production increased with temperature and NaCl concentration, but the use of brackish solutions led to a higher quality product, as compared to the brines, with lower concentration of chlorine and hypochlorous acid. To evaluate the production of ClO2, samples corresponding to two different qualities of the electrogenerated solutions underwent stripping to exhaust chlorine, before being mixed with hydrogen peroxide (H2O2) and sulfuric acid. Results showed that using a chlorate solution obtained from the electrolysis of 20 g L−1 NaCl solution at 50 mA cm−2 and passing 57.35 Ah L−1, a maximum concentration of 33.3 mmol L−1 ClO2 could be attained, which corresponds to a maximum conversion of 48.75%. CONCLUSIONS Efficiency of the synthesis depends on both the purity of chlorate and the H2O2/ClO3− ratio. This confirms that in-situ electrogenerated chlorate can be used to manufacture ClO2, but there are still many gaps to be overcome and further work must be carried out to optimize the production of the desired oxidant in a portable ClO2 device. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Leaching of Molybdenite by Hydrochloric Acid Solution Containing Sodium Chlorate

Abstract: Molybdenum is widely used in many materials; thus, its recovery from ores and secondary resources has attracted considerable attention. In this study, the leaching of molybdenite ore using hydrochloric acid containing sodium chlorate as an oxidizing agent was studied. The effects of several variables, such as the concentrations of HCl and NaClO 3 , reaction temperature and time, and pulp density, on the leaching of the ore were investigated. Under strong acidic and oxidizing conditions, the sulfide in the ore was dissolved as a sulfate ion, which formed gypsum with Ca(II), leading to a decrease in the leaching percentage of Mo(VI) from the ore. The leaching percentage of molybdenum was greater than 90%, while those of iron, calcium, and silicon were 38, 29, and 67%, respectively, under the optimum conditions: 2.0 M HCl, 0.5 M NaClO 3 , pulp density of 5 g/L, temperature of 90 °C, and treatment time of 60 min.

Pulsed spin-locking of spin-3/2 nuclei: 39K-NQR of potassium chlorate.

Abstract: A model was developed for predicting a locked signal under a series of refocusing pulses for Nuclear Quadrupole Resonance (NQR) of spin I=32 and tested with a powder of KClO3. This work represents the first direct NQR detection of the 39K line of potassium chlorate. The characteristic time constants, T1,T2e and T2∗, were measured to determine the detectability of potassium chlorate via 39K-NQR. The echo train T2e was found to be strongly dependent on the refocusing pulse-spacing and weakly dependent on the refocusing pulse strength. The optimal angles of the excitation and echo pulse for a pulse train were also determined, as well as, the resonance-frequency dependence on sample temperature.

Sensor Data Fusion as an Alternative for Monitoring Chlorate in Electrochlorination Applications

Abstract: As chlorate concentrations have been found to be harmful to human and animal health, governments are increasingly demanding strict control of the chlorate concentration in drinking water. Since there are no chlorate sensors available, the current solution is sampling and laboratory analysis. This is costly and time consuming. The aim of this work was to investigate Sensor Data Fusion (SDF) as an alternative approach, with a focus on chlorate formation in the electrochlorination process, and design an observer for the real-time estimation of chlorate. The pH, temperature and UV-a absorption were measured in real time. A reduced-order nonlinear model was derived, and it was found to be detectable. An Extended Kalman Filter (EKF), based on this model, was then used to estimate the chlorate formation. The EKF algorithm was verified experimentally and was found to be capable of accurately estimating chlorate concentrations in real time. Electrochlorination is an emerging and efficient method of disinfecting drinking water. Soft sensing of chlorate concentrations, as proposed in this paper, may help to better control and manage the process of electrochlorination.

sodium chlorate poisoning

Abstract: This datasheet on sodium chlorate poisoning covers Identity, Hosts/Species Affected, Diagnosis.

Exploring the Mechanism of Cr(VI) Catalyzed Hypochlorous Acid Decomposition **

Abstract: Chlorate is produced through electrolysis of a chloride containing electrolyte in an undivided cell. Cr(VI) is added to the electrolyte in order to minimize the amount of oxygen formed through the homogeneous decomposition of hypochlorite. Despite the importance of Cr(VI) for the chlorate process we posses only very limited knowledge regarding the active Cr(VI) species and mechanisms through which it aids chlorate formation and inhibits O2 evolution. Using density functional theory (DFT) modeling we present for the first time a detailed reaction mechanism for the chromate catalyzed chlorate formation. Our calculations indicate, that the reaction is initialized by the formation of a Cr(VI)‐O−ClOCl species which forms Cr(VI)‐OClO intermediate. This step is found to be rate determining with a rate constant which is comparable to the disproportionation reaction without catalyst. Chlorate is then obtained either through an uncatalyzed oxidation of chlorite to chlorate or the nucleophilic attack of OCl− followed by a second Cl− elimination step. The comparison of the activity of the different Cr(VI) species reveals that only CrO42− is active whereas HCrO4− and Cr2O72− display sluggish kinetics.

pH control in sodium chlorate cell for energy efficiency using PSO-FOPID controller

Abstract: Industrial sodium chlorate production is a highly energy-intensive electro-chemical process. If the pH of the chlorate cell is not controlled, the current efficiency drops from 99% to as low as 66.66%. Hence control of chlorate cell pH is very significant for energy-efficient sodium chlorate production. This study puts forward a fractional order PID controller for controlling the pH of the sodium chlorate cell. The tuning of FOPID controller variables is affected by employing particle swarm optimization. The highlight of the controller is that it is flexible, easy to deploy and the time of computation is significantly low as few parameters are needed to be adjusted in PSO. The performance analysis of the suggested FOPID-PSO controller was studied and compared with the traditional PI controller and PID controller using time-domain provisions like settling time, rise time and peak overshoot and error indicators like integral square error (ISE), integral absolute error (IAE), and integral time absolute error (ITAE). FOPID controller employing PSO proved to perform well compared to conventional controllers with 0.5 sec settling time and 0.1 sec rise time. This demonstrates that the FOPID-PSO controller has better setpoint tracking, which is very essential for the process under consideration.

A Study on the Optimal Management Technology of the On-site Sodium Hypochlorite Generator for Disinfection By-products Reduction

Abstract: Objectives : The purpose of this study is to suggest operating conditions that can minimize the disinfection by-products of sodium hypochlorite produced in on-site sodium hypochlorite generators.Methods : The characteristics of disinfection by-products were investigated by operating conditions (dissolved water type, brine concentration, temperature of electrolytic cell inflow water, pH of electrolytic cell inflow water and electrolyzer current density) using a on-site sodium hypochlorite generator(5 kg/day).Results and Discussion : The concentration of disinfection by-products (chlorate, bromate) according to the type of dissolved water was found to be high in the order of softened water > tap water > RO treated water. As the brine concentration increased, chlorate decreased and bromate increased. The optimal saline concentration was found to be 3% or more. As temperature of electrolytic cell inflow water increases,, chlorate decreases and bromate increases. The difference in the concentration of disinfection by-products(chlorate, bromate) according to the pH of electrolytic cell inflow water is not large, and the appropriate pH is determined to be about 7 when the free available chlorine and disinfection by-products are taken into account. Also, as the current density increases, the chlorate increases and bromate showed a decreasing trend.Conclusion : It has been shown that the concentration of disinfection by-products can be minimized when operating within the operating range suggested by the on-site sodium hypochlorite generator manufacturer, and some operating conditions are thought to have been suggested by the manufacturer to protect the electrolyzer cells. As the market for on-site sodium hypochorite generator gradually expands, it is expected that improved facilities will be continuously released in consideration of the stricter standards for disinfection by-products.

Influence of a Static Magnetic Field on the ⟨100⟩ Growth Rates of Sodium Chlorate Crystals from Aqueous Solution

Abstract: The results of the study of the influence of a static magnetic field of 55 ± 3 mT on the growth rates of diamagnetic sodium chlorate crystals in the direction ⟨100⟩ will be presented. Two groups of experiments were performed in the same solution supersaturation range of 0.89–1.78%, the first in zero field conditions, and the second in an applied magnetic field. The results show that crystals nucleated and grown in a static magnetic field have higher mean growth rates in the ⟨100⟩ direction than crystals in a zero field. Also, X-ray analyses suggest that crystals nucleated and grown in a magnetic field may have a higher lattice constant. Possible mechanisms and possible reasons for these phenomena are discussed.