Chlorate Ions Research Articles

Effect of Chlorate Ion and Bromate Ion on the Potassium Permanganate Consumed in Swimming Pools Water

The concentrations of chlorate (ClO3−) and bromate (BrO3−), generated from sodium hypochlorite (NaClO) used as bactericidal agents in a swimming pool collected in Yokohama, were higher than environmental quality standards for water pollution in Japan. In this study, we investigated the effect of chlorate and bromate on the potassium permanganate consumed, KMnO4 in the swimming pool. It was found that potassium permanganate consumed decreased upon the addition of chlorate and bromate to tap and swimming-pool water, while the total organic carbon (TOC) concentration was not affected. The effect of bromate on the potassium permanganate consumed was about 18-times higher than the effect of chlorate, although the mechanism was not cleared. Our results suggested that careful attention is required concerning sanitation of a swimming pool, even though the potassium permanganate consumed as organic pollutants was low.

Activated Nickel Platform for Electrochemical Sensing of Phosphate

We report here a highly selective enzymeless approach for the determination of phosphate (PO(4)(3-)) by flow injection analysis (FIA). In this system, the activation of barrel plated nickel electrode (Ni-BPE) in alkaline media to form a Ni(OH)(2)/NiO(OH) film was found to trigger the adsorption of phosphate at the electrode surface. Based on the suppressed current of the electrocatalytic oxidation of glucose at the activated Ni-BPE in 0.1 M NaOH solution caused by adsorption of phosphate, we develop an FIA detection scheme for the determination of phosphate. Under the optimized conditions of flow rate = 300 microL/min and detection potential = 0.55 V vs Ag/AgCl with 25 microM glucose in 0.1 M NaOH as carrier solution, the calibration curve showed a linear range up to 1 mM. Possible interferences from the coexisting ions were also investigated. The results demonstrated that sensor could be used for the determination of phosphate in the presence of nitrate, chloride, sulfate, acetate, oxalate, carbonate, and some anionic species of toxicological and environmental interest, such as chlorate, chromate, and arsenate ions. The electrode can be effectively regenerated without extra treatment under the hydrodynamic condition. For eight continuous injections of 40 microM PO(4)(3-), a relative standard deviation of 0.28% was obtained, indicating good reproducibility of the proposed method. The detection limit (S/N = 3) was calculated as 0.3 microM.

Rapid analysis of perchlorate, chlorate and bromate ions in concentrated sodium hypochlorite solutions

A sensitive, rapid, and rugged liquid chromatography with tandem mass spectrometry (LC–MS/MS) method for measuring concentrations of perchlorate, chlorate, and bromate ions in concentrated sodium hypochlorite solutions is presented. The LC–MS/MS method offers a practical quantitation limit (PQL) of 0.05 μg L −1 for ClO 4 −, 0.2 μg L −1 for BrO 3 −, and 0.7 μg L −1 for ClO 3 − and a sample analysis time of only 10 min. Additionally, an iodometric titration technique was compared with the LC–MS/MS method for measurement of chlorate ion at high concentration. The LC–MS/MS method was the most reproducible for chlorate concentrations below 0.025 M while the iodometric titration method employed was the most reproducible above 0.025 M. By using both methods, concentrations of chlorate can be measured over a wide range, from 0.7 μg L −1 to 210 g L −1 in hypochlorite ion solutions. Seven quenching agents were also evaluated for their ability to neutralize hypochlorite ion, thereby stopping formation of perchlorate ion in solution, without adversely impacting the other oxyhalide ions. Malonic acid was chosen as the quenching agent of choice, meeting all evaluation criteria outlined in this manuscript.

Evaluation of Oxalate Decarboxylase and Oxalate Oxidase for Industrial Applications

Increased recirculation of process water has given rise to problems with formation of calcium oxalate incrusts (scaling) in the pulp and paper industry and in forest biorefineries. The potential in using oxalate decarboxylase from Aspergillus niger for oxalic acid removal in industrial bleaching plant filtrates containing oxalic acid was examined and compared with barley oxalate oxidase. Ten different filtrates from chemical pulping were selected for the evaluation. Oxalate decarboxylase degraded oxalic acid faster than oxalate oxidase in eight of the filtrates, while oxalate oxidase performed better in one filtrate. One of the filtrates inhibited both enzymes. The potential inhibitory effect of selected compounds on the enzymatic activity was tested. Oxalate decarboxylase was more sensitive than oxalate oxidase to hydrogen peroxide. Oxalate decarboxylase was not as sensitive to chlorate and chlorite as oxalate oxidase. Up to 4 mM chlorate ions, the highest concentration tested, had no inhibitory effect on oxalate decarboxylase. Analysis of the filtrates suggests that high concentrations of chlorate present in some of the filtrates were responsible for the higher sensitivity of oxalate oxidase in these filtrates. Oxalate decarboxylase was thus a better choice than oxalate oxidase for treatment of filtrates from chlorine dioxide bleaching.

Effect of Hofmeister anions on micellization and micellar growth of the surfactant cetylpyridinium chloride

Controlling the morphological characteristics of micellar solutions is important for surfactant performance and for achieving desired properties. In this work we study how monovalent anions of the lyotropic series affect micellization, micellar transitions, and micellar growth of the cationic surfactant N-cetyl pyridinium chloride (CPyCl), with the aim of achieving a tool to methodically tune these self-assembly characteristics. For the first time, a set of ions of the Hofmeister series were studied by combining indirect (surface tension, conductivity, optical absorption, viscosity, dynamic light scattering) and direct-imaging cryogenic-transmission electron microscopy (cryo-TEM). Following recent literature on anionic surfactants, we considered the pyridinium headgroup as a chaotropic cation, interacting with cosmotrope and chaotrope anions (Cl(-), Br(-), NO(3)(-), ClO(3)(-)). We show that the micelles' structure is strongly influenced by both the nature and concentration of added anions and their location in the lyotropic series, but the lyotropic number by itself cannot explain all the effects measured. Especially interesting was the relatively small effect of the chlorate ion on the CMC, but its large effect on micellar transition and growth. We further test the influence of a hydrotrope on the first and second CMC and micellar growth, and compare it with the data obtained with the inorganic salts.

Spectrophotometric determination of chlorate ions in drinking water

Drinking water treated with chlorine or chlorine dioxide contains a mixture of different chlorine species. Their identification, especially at low concentrations, is still problematic because of the number of compounds produced, especially when mixtures of chlorine and chlorine dioxide are used. This research investigated the determination of trace chlorate concentrations in drinking water in the presence of chlorite ion by spectrophotometry. Spectrophotometric methods for the determination of chlorate ion are uncommon because these methods are affected by the presence of chlorite ions in drinking water. The aim of this research was to determine small amounts of chlorate impurities in the presence of chlorite ions by spectrophotometry based on the production of a coloured haloquinone by reaction of chlorate with benzidine in a hydrochloric acid medium. The results showed that the proposed spectrophotometric method is rapid, accurate and simple. The method was also compared with conventional ion chromatography.

Reversed flow injection spectrophotometric determination of chlorate

An interfacing has been developed to connect a spectrophotometer with a personal computer and used as a readout system for development of a simple, rapid and sensitive reversed flow injection (rFI) procedure for chlorate determination. The method is based on the oxidation of indigo carmine by chlorate ions in an acidic solution (dil. HCl) leading to the decrease in absorbance at 610 nm. The decrease in absorbance is directly related to the chlorate concentration present in the sample solutions. Optimum conditions for chlorate were examined. A linear calibration graph over the range of 0.1–0.5 mg L −1 chlorate was established with the regression equation of Y = 104.5 X + 1.0, r 2 = 0.9961 ( n = 6). The detection limit (3 σ) of 0.03 mg L −1, the limit of quantitation (10 σ) of 0.10 mg L −1 and the RSD of 3.2% for 0.3 mg L −1 chlorate ( n = 11) together with a sample throughput of 92 h −1 were obtained. The recovery of the added chlorate in spiked water samples was 98.5 ± 3.1%. Major interferences for chlorate determination were found to be BrO 3 −, ClO 2 −, ClO − and IO 3 − which were overcome by using SO 3 2− (as Na 2SO 3) as masking agent. The method has been successfully applied for the determination of chlorate in spiked water samples with the minimum reagent consumption of 14.0 mL h −1. Good agreement between the proposed rFIA and the reference methods was found verified by Student's t-test at 95% confidence level.

From Isocratic Data to a Gradient Elution Retention Model in IC: An Artificial Neural Network Approach

Gradient elution is used in ion chromatography to achieve rapid analysis with reasonable separation. Optimization and prediction of the gradient is clearly a multidimensional problem, however. One approach to prediction of gradient retention behavior is based on isocratic experimentation. In this work, a gradient model for simultaneous prediction of the retention behavior of fluoride, chlorite, chloride, chlorate, nitrate, and sulfate ions, on the basis of isocratic experimental data, is proposed. An artificial neural network was used to predict isocratic results; the network was optimized with regard to the number of data in the training set (25) and number of neurons in the hidden layer (6). A slight systematic error was observed in the isocratic prediction, but this did not effect gradient prediction. Good predictions were achieved for all the anions investigated (average error 1.79%). Deviations were somewhat higher for prediction of sulfate retention than for the other anions, probably because of the higher charge and larger size of sulfate in comparison with the other ions examined.

Ozone enhanced activity of aqueous titanium dioxide suspensions for photodegradation of 4-chloronitrobenzene

The TiO 2/UV/O 3 process has been employed to remove 4-chloronitrobenzene (4-CNB) and compared to UV/air, O 3, TiO 2/O 3, TiO 2/UV/O 2 and UV/O 3 five parallel oxidation pathways. The reaction activities of these six processes were tested in aqueous using electron paramagnetic resonance (EPR) spin trapping technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin trap. Moreover, the effects of ozone dosage, catalyst dosage and initial solution pH on the degradation of 4-CNB by TiO 2/UV/O 3 process were also investigated. Results showed that the TiO 2/UV/O 3 is the most efficient process for complete mineralization of 4-CNB since the combination of photocatalytic oxidation with ozone has a synergistic effect. The relative intensity of DMPO- OH follows the order of UV/air < O 3 < TiO 2/O 3 < UV/O 3 < TiO 2/UV/O 2 < TiO 2/UV/O 3. In TiO 2/UV/O 3 process, the ozone and catalyst dosage are found to have a significant impact on the process efficiency whereas initial pH has relatively less effect. Chlorine atoms of 4-CNB are absolutely oxidized to chloride anions when the ozone dosage in the range of 5–18 mg/min, or the catalyst dosage ranging from 1.0 to 2.0 g/L. Part of chloride anions would be further oxidized to chlorate(V) ions if the ozone dosage exceeds 24 mg/min, or the catalyst dosage exceeds 2.0 g/L.

The solubility of ozone and kinetics of its chemical reactions in aqueous solutions of sodium chloride

The solubility of ozone and the kinetics of its decomposition and interaction with chloride ions in a 1 M aqueous solution of NaCl at 20°C and pH 8.4–10.8 were studied. The ratio between the concentration of O3 in solution and the gas phase was found to be 0.16 at pH 8.4–9.8. The concentration of dissolved ozone decreased sharply as pH increased to 10.8 because of a substantial increase in the rate of its decomposition. It was observed for the first time that the interaction of O3 with Cl− in alkaline media resulted in the formation of ClO3− chlorate ions. The dependence of the rate of formation of ClO3− on pH was determined; its maximum value was found to be 9.6 × 10−6 mol l−1 min−1 at pH 10.0 and the concentration of ozone at the entrance of the reactor 30.0 g/m3. A spectrophotometric method for the determination of chlorate ions (concentrations 1 × 10−5−3 × 10−4 M) in aqueous solutions was suggested.

Evaluation of chlorite and chlorate genotoxicity using plant bioassays and in vitro DNA damage tests

In the last few years chlorine dioxide has been increasingly used for disinfecting drinking water in many countries. Although it does not react with humic substances, chlorine dioxide added to water is reduced primarily to chlorite and chlorate ions, compounds that are under investigation for their potential adverse effects on human health. The aim of this research was to study the genotoxicity of chlorite and chlorate and their mixtures. The end-points included two plant tests (chromosomal aberration test in Allium cepa and micronucleus assay in Tradescantia, carried out at different times of exposure) and two genotoxicity tests in human HepG2 cells (comet assay and cytokinesis-blocked micronucleus test). Preliminary toxicity tests were carried out for both plant and HepG2 assays. The results showed that chlorite and chlorate are able to induce chromosomal damage to plant systems, particularly chromosomal aberrations in A. cepa root tip cells, even at concentrations lower than the limit established by Italian normative law and WHO guidelines. In HepG2 cells increased DNA damage was only observed for chlorate at the lowest concentration. No increase in micronuclei frequency was detected in any of the samples tested in human HepG2 cells.

Product and by-product formation in electrolysis of dilute chloride solutions

The results of an experimental study on electrochemical disinfection of water are presented. Attention was paid to the behaviour of chlorine compounds during electrolysis of water containing chlorides, with particular regard to the selectivity of the process towards the production of oxidising agents. Two reactor configurations were tested: a stirred tank cell and a filter press cell inserted in a hydraulic circuit. Both cells were equipped with boron doped diamond (BDD) anodes. Experiments were performed in batch and continuous mode. The effect of such operating parameters, current density, stirring rate or recirculating flow rate, on the behaviour of the process was investigated. The results at BDD anodes show that low current densities and perfect mixing of the system should be adopted in order to obtain high values of the concentration of oxidising agents avoiding the formation of such undesired by-products as chlorite, chlorate and perchlorate ions. Runs were also performed in which BDD was substituted by a commercial (Ti/RuO2) DSA anode and the results obtained with the two materials are compared.

Localized passivity breakdown of iron in chlorate- and perchlorate-containing sulphuric acid solutions: A study based on current oscillations and a point defect model

Current oscillations are used to study the effect of chlorate and perchlorate ions on the iron passivity in sulphuric acid solutions. Quasi steady-state current–potential and potentiostatic current–time curves show the emergence of complex current oscillations, besides the simple periodic ones attributed to general corrosion occurring across the passive–active transition of the Fe|0.75 M H 2SO 4 electrochemical system. The complex current oscillations arising at the iron passive state are indicative of pitting corrosion. Experimental results support that pitting is due to chlorides produced via the reduction of chlorates and perchlorates by ferrous ions either during the active phase of current oscillations or in the passive phase during the H +-catalyzed dissolution of the oxide. Thus, chloride is the aggressive ion that causes pitting corrosion and not chlorates and perchlorates themselves. Chloride production induced via the reduction of perchlorates is much slower than that induced by chlorates. A point defect model (PDM) is employed to explain the oxide growth and its breakdown induced by general and pitting corrosion.

Disinfection By-Products (DBPs) in Drinking Water from Eight Systems Using Chlorine Dioxide

Abstract A study was initiated to determine the presence of organic disinfection by-products (DBPs) in drinking water treated with chlorine dioxide (ClO2). One potential advantage for the use of ClO2 as a disinfectant is the reduced formation of organic DBPs. Generally, water treated with ClO2 produces chlorite and chlorate ions, but there is limited information regarding the presence of halogenated organic DBPs. Eight systems that use chlorine dioxide as part of the water disinfection process were investigated. All systems in this study applied chlorine as a primary or secondary disinfectant in addition to ClO2. To evaluate seasonal and spatial variations, water samples were collected during cold water (February to March 2003) and warm water (July to August 2003) months at five sites for each system: raw water (R, before treatment), treated water (T, after treatment but before distribution), and three points along the same distribution line (D1, D2, D3). Sampling and analysis were conducted according to established protocols. A suite of 27 organic DBPs including haloacetic acids (HAA), trihalomethanes (THM), haloacetonitriles (HAN), haloketones, haloacetaldehydes (HA), chloropicrin, and cyanogen chloride were examined. In addition, the concentration of oxyhalides (chlorite and chlorate ions) and auxiliary parameters were also determined. Chlorite was found in treated (T) and distributed (Dx) waters. The chlorite ion levels decreased along the distribution system (T &amp;gt; D1 &amp;gt; D2 &amp;gt; D3). At T sites, the levels ranged from 10 to 870 µg/L (winter), and from 300 to 1,600 µg/L (summer). Chlorite was not found in treated or distributed water in the one system that used ozone. Chlorate ion levels ranged from 20 to 310 µg/L (winter), and 80 to 318 µg/L (summer). Chlorate levels remained relatively constant throughout the distribution system. THM and eight HAA (HAA8) accounted for approximately 85% of the total DBPs (wt/wt) analyzed, followed by total HA (up to 7%) and HAN (3%). THM in distributed water were found at concentrations between 1.8 and 30.6 µg/L (winter), and 3.3 and 93.6 µg/L (summer). For HAA8, the levels ranged from 13 to 52 µg/L (winter), and 16 to 111 µg/L (summer). Chloral hydrate ranged from 0.2 to 5.2 µg/L (winter), and 0.4 to 12.2 µg/L (summer). The temporal and spatial variations observed in previous studies were confirmed in the current study as well.

HPLC determination of chlorate metabolism in bovine ruminal fluid§

Salmonella and Escherichia coli are two bacteria that are important causes of human and animal disease worldwide. Chlorate is converted in the cell to chlorite, which is lethal to these bacteria. An HPLC procedure was developed for the rapid analysis of chlorate (ClO3 −), nitrate (NO3 −), and nitrite (NO2 −) ions in bovine ruminal fluid samples. Standard curves for chlorite, nitrite, nitrate, and chlorate were well defined linear curves with R2 values of 0.99846, 0.99106, 0.99854, and 0.99138, respectively. Concentrations of chlorite could not be accurately determined in bovine ruminal fluid because chlorite reacts with or binds a component(s) or is reduced to chloride in bovine ruminal fluid resulting in low chlorite measurements. A standard curve ranging from 25 to 150 ppm ClO3 − ion was used to measure chlorate fortified into ruminal fluid. The concentration of chlorate was more rapidly lowered (P < 0.01) under anaerobic compared to aerobic incubation conditions. Chlorate alone or chlorate supplemented with the reductants sodium lactate or glycerol were bactericidal in anaerobic incubations. In anaerobic culture, the addition of sodium formate to chlorate-fortified ruminal fluid appeared to decrease chlorate concentrations; however, formate also appeared to moderate the bactericidal effect of chlorate against E. coli. Addition of the reductants, glycerol or lactate, to chlorate-fortified ruminal fluid did not increase the killing of E. coli at 24 h, but may be useful when the reducing equivalents are limiting as in waste holding reservoirs or composting systems required for intense animal production. §Mention of trade names, proprietary products, or specific equipment is solely for the purpose of providing specific information and does not constitute a guarantee, warranty or endorsement by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.

Photochemically Induced Autocatalysis in the Chlorate Ion−Iodine System

Light initiates an autocatalytic reaction sequence in the chlorate ion−iodine reaction. A previous report on the same system (Oliveira, A. P.; Faria, R. B. J. Am Chem. Soc. 2005, 127, 18022−18023.) failed to recognize the role of photoinitiation by the diode-array spectrophotometer used in the experiments. A mechanism is proposed to interpret the observations.

Product and by-product formation in laboratory studies on disinfection electrolysis of water using boron-doped diamond anodes

Boron-doped diamond (BDD) electrodes were studied with respect to the formation of inorganic by-products in water electrolysis. Experiments in non-divided cells were performed with systems containing sulphate, chloride, chlorite, chlorate and nitrate ions. Discontinuous experiments in thermostated cells with rotating disk diamond anodes and expanded mesh IrO 2 cathodes were carried out at 20 °C. Current density was varied between 50 and 300 A m −2. Ion chromatography was mainly used for species detection. It was not possible to demonstrate the decomposition of sulphate although a slight tendency seems to exist in some experiments. Hydrogen peroxide is one of the anodic and cathodic by-products. Active chlorine is detectable at higher chloride concentrations compared with the use of mixed oxide anodes (MIO). One reason for this is the reaction of formed chlorine with ozone or hydrogen peroxide. Chlorate can be formed electrolysing chloride, hypochlorite and chlorite solutions. Perchlorate formation was detected. Cathodic processes are responsible for the formation of nitrite ions and ammonia. If chlorine is present, the formation of monochloramine is one possible side reaction. Results show that the processes are very complex. Reaction spectra may vary from case to case. Perchlorate formation is a high risk in drinking water treatment.

The Effect of an Experimental Chlorate Product on Salmonella Recovery of Turkeys when Administered Prior to Feed and Water Withdrawal

Previously, an experimental chlorate product (ECP) has been observed to reduce Escherichia coli and Salmonella infections in swine, cattle, and broilers. The following studies were performed to investigate the effects of different concentrations and durations of administering ECP on crop and ceca Salmonella typhimurium (ST) colonization of turkeys. In 2 separate trials, each conducted with 2 replicates, 15-wk-old turkey toms were challenged with 107 to 109 cfu of ST. In Experiment 1, toms were administered 0, 0.5, 1.0, 2.0, or 4.0× of ECP (a 1.0× concentration is equivalent to a 15 mM chlorate ion concentration) in the drinking water for 38 h. In Experiment 2, toms were administered a 2× concentration of ECP in the drinking water for 0, 14, 26, or 38 h prior to water withdrawal. All treatments were followed by a 10-h water withdrawal and an 8-h feed withdrawal prior to organ sampling. In Experiment 1, turkeys provided ECP had significantly (P < 0.05) lower populations and incidences of crop (>1.4 log reduction) and ceca (>0.6 log reduction) ST as compared with control birds (2.1 and 0.94 log ST average for all trials, respectively), with little or no additional benefit from administration of higher ECP concentrations. In Experiment 2, toms provided ECP had lower populations of crop (>2.2 log reduction) and ceca (>1.5 log reduction) ST when compared with controls (3.1 and 1.8 log ST, respectively). Again, there appeared to be little benefit in longer administration intervals on quantitative reduction of ST. These experiments suggest that the ECP significantly reduces Salmonella colonization in commercial turkeys when administered prior to feed and water withdrawal.

Chlorates induce pitting corrosion of iron in sulfuric acid solutions: An analysis based on current oscillations and a point defect model

Current oscillatory phenomena were used to investigate the effect of chlorates on the passive state of iron in sulfuric acid solutions. Experimental results show that chlorates cause pitting corrosion, besides general corrosion. It is shown that pitting is not due to the chlorate ion itself, but to chlorides produced via the reduction of chlorates by ferrous ions. General and pitting corrosion are explained in terms of a point defect model proposed to describe the oxide growth and breakdown.

Cathodic current efficiency in the chlorate process

Sodium chlorate is produced in undivided electrolysis cells. Hydrogen is evolved on the cathodes, usually made of steel, while chloride ions are oxidised to chlorine on the anodes, usually DSA®s. Parasitic cathodic reactions, lowering the cathodic current efficiency (CE), are the reduction of hypochlorite and chlorate ions. These reactions are suppressed by the addition of Cr(VI) to the electrolyte. In this work the effects that time of the electrolysis, chromate concentration and interruption of the electrolysis process have on CE has been investigated. New steel, as well as steel samples cut from cathodes used in a chlorate plant, were used as cathode material. Laboratory experiments in a divided cell were made to determine the rate of hydrogen production, and thereby indirectly CE, at varying operating conditions. It was found that the chromate concentration is important for the CE in the range 0.5–6 g l−1 Na2Cr2O7. The CE was higher on new steel than on the used steel, which had a more corroded and inhomogeneous surface. When starting the electrolysis the CE was initially low, at a value depending on the operating conditions, but increased with time of polarisation. The time to reach an approximate steady CE was generally in the order of hours. Electrolysis shut downs in the presence of hypochlorite (≤ 3 g l−1 NaClO) resulted in corrosion of iron and a low CE when restarting the process. After one such corrosion shut down the new steel showed as low CE as the used steel. When restarting the electrolysis after a shut down without hypochlorite the CE was higher than before the shut down. Current densities of a simulated bipolar plate during a shut down were measured to 50–150 A m−2, resulting from oxidation of steel and reduction of oxy chlorides on the catalytic DSA® electrode.