Bromate In Water Research Articles

Nanostructured Catalysts for the Continuous Reduction of Nitrates and Bromates in Water

Nanostructured C-based catalysts have been developed to be used in continuously operated (open-flow) reactors for the removal of bromates and nitrates from polluted water. The catalysts contain transition-metal (Pd, Cu, and Sn) nanoparticles (NPs) supported on activated carbon fiber fabrics, honeycomb monoliths, and sintered metal fiber (SMF) filters coated by carbon nanofibers (CNF). All catalysts were effective in the reduction of nitrates and bromates present in polluted natural and industrial waters. The best results for nitrate removal in terms of selectivity to N2 were obtained with the NPs of Pd–Sn (2:1) supported on a mesoporous 5% CNF/SMF. In bromate removal, the same 5% CNF/SMF support with monometallic Pd0 NPs showed the highest performance because of suppressed mass-transport limitations. Finally, the (0.3% Pd + 0.15% Sn)/5% CNF/SMF catalyst was tested in simultaneous bromate and nitrate removal from synthetic polluted waters and shown to be suitable for attaining pollutant concentrations below the legislation limits (50 mg/L for nitrates and 10 μg/L for bromates since 2009 in Europe). The continuously operated reactor designed as a bubble column staged with two different types of the fibrous catalysts has been proposed for the simultaneous bromate and nitrate removal from polluted waters.

Highly efficient catalytic reduction of bromate in water over a quasi-monodisperse, superparamagnetic Pd/Fe3O4 catalyst

A novel quasi-monodisperse, superparamagnetic Pd/Fe3O4 catalyst was synthesized for effective catalytic bromate reduction. The catalyst was prepared by dispersing nanoparticles of Pd (weight percent up to 1%) on the surface of superparamagnetic Fe3O4 microspheres with 300–500 nm in diameter and 10–20 nm in grain size. Complete reduction of bromate by this Pd/Fe3O4 catalyst was demonstrated within a short period (<2 h) over a range of pH values, in the presence of a variety of co-existing ions, and after multiple cycles. In addition, the superparamagnetic nature of the catalyst enhanced its good dispersion in water during water treatment when there was no external magnetic field, and its high saturation magnetization allowed an easy magnetic separation from water when an external magnetic field was applied after the water treatment. Thus, it could be easily recycled and reused, further enhancing its application potential.

Ruthenium-catalyzed oxidation of alcohols by bromate in water

The polypyridylruthenium(II) complex, cis-[Ru(2,9-Me2phen)2(OH2)2]2+, is a highly efficient catalyst for the oxidation of alcohols to carbonyl products in water using sodium bromate (NaBrO3) as the terminal oxidant. Excellent conversions and yields are readily achieved at room temperature.

Cisapride a green analytical reagent for rapid and sensitive determination of bromate in drinking water, bread and flour additives by oxidative coupling spectrophotometric methods

Green analytical methods using Cisapride (CPE) as green analytical reagent was investigated in this work. Rapid, simple, and sensitive spectrophotometric methods for the determination of bromate in water sample, bread and flour additives were developed. The proposed methods based on the oxidative coupling between phenoxazine and Cisapride in the presence of bromate to form red colored product with max at 520nm. Phenoxazine and Cisapride and its reaction products were found to be environmentally friendly under the optimum experimental condition. The method obeys beers law in concentration range 0.11–4.00gml−1 and molar absorptivity 1.41×104Lmol−1cm−1. All variables have been optimized and the presented reaction sequences were applied to the analysis of bromate in water, bread and flour additive samples. The performance of these method was evaluated in terms of Student’s t-test and variance ratio F-test to find out the significance of proposed methods over the reference method. The combination of pharmaceutical drugs reagents with low concentration create some unique green chemical analyses.

Sensitive and robotic determination of bromate in sea water and drinking deep-sea water by headspace solid-phase micro extraction and gas chromatography–mass spectrometry

A robotic method has been established for the determination of bromate in sea water and drinking deep-sea water. Bromate in water was converted into volatile derivative, which was measured with headspace solid-phase micro extraction and gas chromatography–mass spectrometry (HS-SPME GC–MS). Derivatization reagent and the HS-SPME parameters (selection of fibre, extraction/derivatization temperature, heating time and; the morality of HCl) were optimized and selected. Under the established conditions, the detection and the quantification limits were 0.016μgL−1 and 0.051μgL−1, respectively, and the intra- and inter-day relative standard deviation was less than 7% at concentrations of 1.0 and 10.0μgL−1. The calibration curve showed good linearity with r2=0.9998. The common ions Cl−, NO3−, SO42−, HPO42−, H2PO4−, K+, Na+, NH4+, Ca2+, Mg2+, Ba2+, Mn4+, Mn2+, Fe3+ and Fe2+ did not interfere even when present in 1000-fold excess over the active species. The method was successfully applied to the determination of bromate in sea water and drinking deep-sea water.

Oxidation and degradation of native wheat starch by acidic bromate in water at room temperature

Native wheat starch was oxidized by benign acidic bromate in water at room temperature. HPLC-ELSD study indicated that starch degraded in the course of oxidation but it still had a polymeric structure characterized by 1H, 13C, HSQC and HMBC NMR measurements. Products were generally water-soluble fragments but the use of a short reaction time and dilute reaction mixture yielded water-insoluble products. Titration of the products showed, that the increase of the starch content and reaction time increased the content of carbonyl and carboxyl groups in the range of 0.5–2.5% and 1.7–17.2%, respectively, in the product fragments. A mechanism for the oxidation reaction was proposed.

Automated solid-phase spectrophotometric system for optosensing of bromate in drinking waters

An automated method based on an optosensor included in a multisyringe flow injection system was developed for the determination of bromate in waters for human consumption. The optosensor was based on the formation of a colored radical cation after oxidation of chlorpromazine by bromate and its selective uptake in a mixed-mode cation exchanger sorbent (Discovery DSC-MCAX), placed on a flow-through spectrophotometric cell. In-line regeneration was attained by methanol + 5% (v/v) ammonia, fostering the application of the same sorbent portion up to 180 determinations. Parameters affecting the reaction development and uptake of the colored compound were studied and optimized, while in-line addition of sulfite (≥0.100 g L−1) prevented interference from hypochlorite. The proposed methodology allowed the determination of bromate up to 50.0 μg L−1, with 0.9 μg L−1 as the limit of detection, meeting the requirements of current EU and USA legislation. Application to real drinking water samples was successful, with a mean recovery of 100.2 ± 2.8% for spiked levels of 5.0, 10.0 and 25.0 μg L−1. Repeatability was good (RSD < 3.6%, n = 10) with a determination throughput of 8 h−1, fostering the application to on-line control of water disinfection processes.

Occurrence and Sources of Bromate in Chlorinated Tap Drinking Water in Metropolitan Manila, Philippines

Significant levels of potentially carcinogenic bromate were measured in chlorinated tap drinking water in Metropolitan Manila, Philippines, using an optimized ion-chromatographic method. This method can quantify bromate in water down to 4.5 μg l⁻¹ by employing a postcolumn reaction with acidic fuchsin and subsequent spectrophotometric detection. The concentration of bromate in tap drinking water samples collected from 21 locations in cities and municipalities within the 9-month study period ranged from 7 to 138 μg l⁻¹. The average bromate concentration of all tap drinking water samples was 66 μg l⁻¹ (n = 567), almost seven times greater than the current regulatory limit in the country. The levels of bromate in other water types were also determined to identify the sources of bromate found in the distribution lines and to further uncover contaminated sites. The concentration of bromate in water sourced from two rivers and two water treatment plants ranged from 15 to 80 and 12 to 101 μg l⁻¹, respectively. Rainwater did not contribute bromate in rivers but decreased bromate level by dilution. Groundwater and wastewater samples showed bromate concentrations as high as 246 and 342 μg l⁻¹, respectively. Bromate presence in tap drinking water can be linked to pollution in natural water bodies and the practice of using hypochlorite chemicals in addition to gaseous chlorine for water disinfection. This study established the levels, occurrence, and possible sources of bromate in local drinking water supplies.

A method for the detection of bromate in brackish water

The objective of this study was to develop a simple yet accurate method for the detection of bromate in brackish water. Typically, bromate is measured by ion chromatography; however, the presence of chloride ions complicates bromate detection using this technique. Where bromide ions are naturally present in the source water to be ozonated, either for drinking water or aquacultural purposes, bromate is formed as a disinfection by-product. As such, the need to measure bromate in brackish water is complicated due to the naturally present chloride ions. The study was carried out in a laboratory setting using a UV-spectrophotometer and an ion chromatograph to verify the results. To examine the robustness of the UV-based method, seven water matrices were used to test the bromate detection method. The bromate method presented herein utilizes a reaction of bromate with iodide followed by detection at a UV absorbance at 352 nm. A key finding from the study was that the concentration of bromate was quickly and accurately determined using spectrophotometry. This method successfully measured bromate in waters containing a broad range of conductivity and avoided interference from other anions. The method detection limit reported for all seven water matrices tested was greater than 0.14 mg L −1, which limits the methods utility to saline solutions.

Spectrophotometric Determination of Bromate in Water Using Multisyringe Flow Injection Analysis

A multisyringe flow injection system for the spectrophotometric determination of bromate in water is proposed, based on the oxidation of phenothiazine compounds by bromate in acidic medium. Several phenothiazines were tested, including chlorpromazine, trifluoperazine, and thioridazine. Higher sensitivity and lower LOD were attained for chlorpromazine. Interference from nitrite, hypochlorite, and chlorite was eliminated in-line, without any changes in the manifold. The automatic methodology using chlorpromazine allowed the determination of bromate between 25 and 750 µg L−1, with LOD of 6 µg L−1, good precision (RSD < 1.6%, n = 10), and determination frequency of 35 h−1.

Development of new methodologies for on-line determination of the bromate ion in samples of water subjected to ozonation treatment

The bromate ion has been identified as an inorganic disinfection by-product (DPB) in water subjected to purification treatment. Its presence arises from the application of oxidation processes to water containing bromide through the action of oxidant agents such as the ozone used in ozonation processes. This ion has been identified as a possible carcinogen by the U.S. Environmental Protection Agency, which recommends a maximum concentration of 10 microgL(-1). The literature reports a broad range of methods for the analysis of bromate in water, among which ion chromatography is the one most widely used, with different detection systems. However, most of the methods described to date require state-of-the-art technology and costly instrumentation, such that they are not readily adaptable to routine analyses. The present work reports a procedure for the spectrophotometric determination of bromate based on the bromination reaction of 3-3' dimethoxybenzidine, o-dianisidine (ODA). The reaction is based on the formation of Br2 in the presence of excess bromide and the later bromination of ODA, generating a product that absorbs at 450 nm. The procedure was set up with Flow Injection Analysis and allows the determination of the analyte in the 8 microg L(-1)-3.3 mg L(-1) range, with a detection limit of 6.0 microg L(-1) and relative standard deviations (n=12, [BrO3-]=8.0 and 30.0 microg L(-1)) of 4.8% and 2.9%, respectively. The determination rate was 10-11 samples/hour.

Bromate formation on the non-porous TiO 2 photoanode in the photoelectrocatalytic system

The increasing use of ozone in water disinfection processes has been the focus of considerable concern in regards to inorganic disinfection by product formation of bromate in waters containing bromide. Due to the public health risk caused by the presence of bromate as a suspected carcinogen, attention had been addressed to the conditions under which bromate is formed. In this study, photoanodic bromine generation and bromate ( BrO 3 - ) formation were investigated using a TiO 2 electrode in a photoelectrocatalytic (PEC) treatment process. The separation of anodic and cathodic reactions in the PEC system resulted in a pH decrease from 9.3 to 3.0 in the photoanode compartment and an increase to 11.0 in the cathode compartment. Under a photo-illumination intensity of 5.7 mW cm −2 UV, a biasing potential of +1.0 V vs SCE, a pH of 6.0 and at a NaBr concentration of 1.0 × 10 −2 M, active bromine formation increased over time with 2.4 × 10 −6 M min −6 rate and reached a steady-state concentration of 1.44 × 10 −4 M in 60 min. Bromate formation was detected after a lag-period of 15 min and exhibited a continuous increasing trend with respect to irradiation time. No bromate formation was observed below pH 6.5 whereas an increasing bromate concentrations and pH up to pH = 8.5 were noted.

Determination of inorganic oxyhalides in drinking water by on-line coupled capillary isotachophoresis— capillary zone electrophoresis

AbstractSome oxyhalides can be found in drinking waters as inorganic disinfection byproducts. An on-line coupled capillary isotachophoresis—capillary zone electrophoresis (CITP-CZE) method was developed for the analysis of chlorate, chlorite and bromate in water. The optimized CITP-CZE electrolyte system consisted of the following: 10 mM—HCl+20 mM—β-Alanine (leading electrolyte), 5 mM—succinic acid (terminating electrolyte), and 10 mM—succinic acid +5 mM—β-Alanine +0.1% HPMC (carrier electrolyte). A clear separation of oxyhalides from other components of drinking water was achieved within 25 min. Method characteristics, i.e., linearity (0–200 ng/mL), accuracy (88–110%), intra-assay (3–5%), quantification limit (5–15 ng/mL), and detection limit (2–5 ng/mL), were determined. Minimum labor requirements, sufficient sensitivity and low running cost are important attributes of this method. It was found that the developed method is useful for the routine analysis of oxyhalides in water.

Bromate assay in water by inductively coupled plasma mass spectrometry combined with solid-phase extraction cartridges.

Based on selective sorption of bromide, bromoacetic acids (BAA) and bromomethanes on solid-phase extraction (SPE) cartridges, a sensitive and convenient method was developed for the determination of bromate in waters by inductively coupled plasma mass spectrometry (ICP-MS). Dionex OnGuard Ag and reversed-phase (RP) cartridges were tested for retention characteristics for bromide, BAA and bromomethanes. When a sample acidified with nitric acid was passed through an RP cartridge, BAA and bromomethanes were retained, afterwards bromide was absorbed as a precipitate of silver bromide and bromate was unretained when the nearly neutral sample passed a combination of Ag and H cartridges. After SPE pretreatment the recovery of bromate was 96-106%, and bromide remaining in the aqueous phase was found to be less than 0.06 microg L(-1) when the original bromide concentrations were less than 5 mg L(-1). Effectiveness of stacked Ag and H cartridges in removing bromide from chloride-containing samples was also examined. Common cations and other anions did not interfere with bromate determination. The detection limit for bromate is 57 ng L(-1). This method has been applied to analyse waters from various sources, and the recovery of the spiked bromate was in the range of 92-107%.

Simultaneous kinetic-spectrophotometric determination of periodate–bromate and iodate–bromate mixtures using the H-point standard addition method

The H-point standard addition method (HPSAM), based on spectrophotometric measurement, for simultaneous determination of periodate–bromate and iodate–bromate mixtures is described. This method is based on the difference between the rates of their reactions with iodide in acidic media. The results showed that simultaneous determinations could be performed with the ratio 1:15–12:1 for periodate–bromate and 15:1–1:15 for iodate–bromate. The proposed method was successfully applied to the simultaneous determination of periodate–bromate and iodate–bromate in water and synthetic samples.

Influence of reagent purity on the ion chromatographic determination of bromate in water using 3,3'-dimethoxybenzidine as a prochromophore for photometric detection.

Variable availability of the purified dihydrochloride salt of 3,3'-dimethoxybenzidine (DMB; ortho-dianisidine) led us to investigate the effects of reagent purity on the analytical results obtained when this reagent is used in the photometric determination of the disinfection byproduct bromate. After analyte ions are separated by ion chromatography, a solution of DMB (post-column reagent) is added to the eluate and the DMB is oxidized, thereby producing a chromophore detected by its absorbance. Although some commercial products of undefined grade performed well, others did not. Variability was also observed between lots of purified material. Sensitivity at low concentrations (< 5 micrograms L-1 BrO3-) varied by a factor of up to 10. In some cases, the lower limit of detection for photometric detection was greater than that obtained using conductivity detection, as high as 5-7 micrograms L-1 BrO3-. An impurity or several impurities are suspected to be responsible for deviations from linearity at low analyte concentrations. This investigation underscores the need for ensuring reagent purity in environmental analyses. Ideally, chemical manufacturers will meet the needs of analytical chemists who test potable water and begin producing a high grade material in sufficient quantities to meet monitoring requirements. The establishment of third-party standards for a spectrophotometric grade of DMB.2HCl would be helpful in ensuring that a variety of manufacturers could supply products of uniformly high quality that would be suitable for the measurement of bromate in public drinking water supplies.