Bromate Reduction In Water Research Articles

Adsorption-coupled Fenton type reduction of bromate in water by high-yield polymer-derived ceramic-supported nano-zerovalent iron

Nano-zerovalent iron (nZVI) is a promising material for the removal of both organic and inorganic pollutants from contaminated water. This study investigates the potential of a novel composite of nZVI on a polymer-derived supporting ceramic (nZVI-PDC) synthesized via the liquid-phase reduction method for the simultaneous adsorption and Fenton-type reduction of bromate anion (BrO3−) in water. The nZVI nanoparticles were effectively anchored onto the PDC by impregnating high-yield carbon in a ferrous sulfate solution. The PDC facilitated the uniform dispersion of nZVI nanoparticles due to its multiple active sites distributed within mesocarbon cavities. The developed nZVI-PDC composite exhibited a high specific surface area of 837 m2 g−1 and an ordered mesoporous structure with a pore volume of 0.37 cm3 g−1. As an adsorbent, the nZVI-PDC composite exhibited a maximum adsorption capacity (qe) of 842 mg g−1 and a partition coefficient (KH) of 10.2 mg g−1 μM−1, as calculated by the pseudo-second-order model. As a catalyst, the composite demonstrated a reaction kinetic rate of 43.5 μmol g−1 h−1 within 6 h at pH 4, using a dosage of 60 mg L−1 nZVI-PDC and a concentration of 0.8 mmol L−1 H2O2. Comparatively, PDC exhibited a qe of 408 mg g−1, KH of 1.67 mg g−1 μM−1, and a reaction rate of 20.8 μmol g−1 h−1, while nZVI showed a qe of 456 mg g−1, KH of 2.30 mg g−1 μM−1, and a reaction rate of 27.2 μmol g−1 h−1. The modelling indicated that the nZVI-PDC composite followed pseudo-second-order kinetics. The remarkable removal efficiency of the nZVI-PDC composite was attributed to the synergistic effects between PDC and nZVI, where PDC facilitated charge transfer, promoting Fe2+ generation and the Fe3+/Fe2+ cycle. Overall, this work introduces a promising adsorption technology for the efficient removal of BrO3− from contaminated aqueous solutions, highlighting the significant potential of the nZVI-PDC composite in water purification applications.

Magnetic Metallic Nanoparticles Coated with Carbon for the Catalytic Removal of Bromate from Water

Bromate, often detected in drinking water, is associated with a significant risk of cancer. Catalytic reduction has been recognized as an effective treatment technique to remove ions by reducing them over metal catalysts in the presence of a reducing agent, usually hydrogen. This work aims to synthesize metallic magnetic nanoparticles of iron oxide (FeO) and mixed iron oxides with manganese (MnFeO), cobalt (CoFeO), and copper (CuFeO) coated with carbon via chemical vapor deposition (C-MNP) to be applied as catalysts to the reduction of bromate in water. The use of magnetic nanoparticles coated with carbon enables catalyst recovery via magnetic separation and takes advantage of the catalytic properties of the carbon materials. The iron particles proved to be the most promising catalysts for the reduction of bromate into bromide, the highest removal being obtained with the CFeO@CVD750 sample, resulting in a 99% conversion after 120 min of reaction under the conditions tested. Due to its magnetic nature, the catalytic material was easily removed after the reaction and applied in four consecutive cycles without losing its catalytic properties. These results highlight the great potential of carbon-coated magnetic nanoparticles for reducing bromate in water.

Catalytic bromate reduction in water by Ru/C via borohydride-based hydrogenation: A comparative study

While H2 gas is conventionally purged during hydrogenation of bromate in the presence of catalysts, the low solubility of H2 gas leads to wasteful consumption of H2 gas. Reductants in solid forms, which act as storage media of H2, would be preferable, and borohydrides, including NaBH4, and NH3BH3 are promising candidates. Although ruthenium (Ru) is an efficient catalyst for releasing H2 from these borohydrides, almost no studies have looked into usage of Ru with borohydrides for reducing bromate, and differences between NaBH4, and NH3BH3 for reducing bromate in the presence of Ru. Therefore, the goal of this study aims to compare hydrogenation of bromate using different borohydrides as well as H2 gas purge under different conditions in the presence of Ru/C as the most representative Ru catalyst. While Ru/C could slowly reduce bromate to bromide, the addition of NaBH4 or NH3BH3 would tremendously accelerate bromate removal and bromide production. Nevertheless, the H2 purge might cause interferences with the entire reaction, thereby leading to ineffective bromate reduction. Moreover, Ru/C+NaBH4 would lead to an even faster bromate reduction because adsorption of BH4– to Ru/C was much more favorable according to the DFT calculation. The Ea of bromate reduction by Ru/C+NaBH4 is also lower than that by Ru/C+NH3BH3, validating the promising advantage of NaBH4 over NH3BH3. Ru/C+NaBH4 could be also reusable for reducing bromate to bromide, demonstrating that borohydrides might be promising alternatives to H2 purge for reducing bromate to bromide in order to achieve even faster and more efficient bromate reduction.

Palladium Impregnation on Electrospun Carbon Fibers for Catalytic Reduction of Bromate in Water

The remediation of bromate in water is a concern due to the reported health issues caused by its ingestion. Catalytic processes, wherein bromate is reduced to non-hazardous bromide, have been studied. In the present work, catalysts of 1% palladium supported in electrospun carbon fibers (Pd-CFs) using different methods for palladium incorporation were prepared. The textural properties, morphology, crystalline structure, and hydrogenation capacity by H2 chemisorption analysis of the Pd-CFs catalysts were characterized. The catalytic tests were performed in a semi-batch reactor, and the obtained results showed different catalytic activity by each prepared Pd-CFs catalyst. The catalysts prepared by incipient wetness impregnation—1% Pd/CF1 and 1% Pd/CF2, using CFs obtained with electrospinning flow rates of 0.5 mL h−1 and 2 mL h−1, respectively—achieved total bromate reduction after 120 min of operation; however, 1% Pd/CF1 obtained total reduction as early as 30 min. Taking into account the catalyst properties, 1% Pd/CF1 showed a good catalytic activity due to CFs morphology obtained using a low electrospinning flow rate, while the Pd incorporation method allowed a high availability of active sites with hydrogenation properties for bromate reduction.

Enhanced reduction of bromate in water by 2-dimensional porous Co3O4 via catalytic hydrogenation

As catalytic hydrogenation is validated as one of the most useful approach to reduce a potential carcinogenic bromate in water, the usage of continuous purge H2 gas and precious metal catalysts are typically required, making it less feasible for practical implementation. Since sodium borohydride (NaBH4) represents a potential alternative source for releasing H2 and non-precious metal catalysts (cobalt (Co)) are usually required to accelerate the hydrolysis of NaBH4 for faster H2 production, the combination between Co-based catalysts and NaBH4 could be favorable for bromate hydrogenation. Especially, it is even more advantageous to fabricate a porous heterogeneous catalyst with high surface area. Thus, this study aims to construct such a novel porous heterogeneous catalyst for reducing bromate using sodium borohydride. Herein, a Co-coordinated framework with TMC ligand (CoTMC) is employed as precursor, which is then transformed into hexagonal porous Co3O4 (HPCO) via one-step calcination. The resultant HPCO possesses remarkable surficial oxygen vacancies as well as textural properties in comparison with Co3O4 NP. Importantly, HPCO could completely reduce bromate to bromide within 20 min. The calculated bromate removal capacity using HPCO and NaBH4 is achieved as 781.25 μmol/g, and the activation energy (Ea) is also calculated as 28.5 kJ/mol. Besides, HPCO also exhibits high catalytic activities for bromate reduction in the presence of various anions. Moreover, HPCO could be also reusable for reducing bromate to bromide over multiple-cycles without any remarkable change of catalytic activities. These features indicate that HPCO is a robust and effective heterogeneous catalyst for bromate reduction in water.

Nature and evolution of Pd catalysts supported on activated carbon fibers during the catalytic reduction of bromate in water

Pd/ACF are active catalysts for the bromate reduction and their activity depends on the Pd crystal size with a pseudo-first order kinetic respect to BrO3− and H2 partial pressure.

Advances in Treatment of Brominated Hydrocarbons by Heterogeneous Catalytic Ozonation and Bromate Minimization.

The formation of carcinogenic bromate ions is a constraint when ozone is used for the remediation of water containing brominated organic materials. With its strong oxidizing ability, ozone rapidly transforms bromide in aqueous media to bromate, through a series of reactions involving hydroxyl radicals. Several strategies, such as limiting the ozone concentration, maintaining pH < 6, or the use of ammonia or hydrogen peroxide were explored to minimize bromate generation. However, most of the above strategies had a negative effect on the ozonation efficiency. The advanced oxidation processes, using catalysts together with ozone, have proven to be a promising technology for the degradation of pollutants in wastewater, but very few studies have been conducted to find ways to minimize bromate formation during this approach. The proposed article, therefore, presents a comprehensive review on recent advances in bromate reduction in water by catalytic ozonation and proposes reaction mechanisms associated with the catalytic process. The main aim is to highlight any gaps in the reported studies, thus creating a platform for future research and a quest to find environment friendly and efficacious catalysts for minimizing bromate formation in aqueous media during ozonation of brominated organic compounds.

Catalytic bromate reduction in water: Influence of carbon support

The classification of bromate as possibly carcinogenic for humans has led to an increasing interest of researchers in the development of effective technologies for its removal from water. Catalytic reduction of bromate into bromide in water under hydrogen flow was studied in detail using Pd and PdCu catalysts supported on multi walled carbon nanotubes with different textural and surface chemical properties. Cu supported catalysts show poor catalytic activity, whereas the coupling of Cu and Pd does not improve the catalytic performance of the Pd supported catalysts, the exception being the bimetallic catalysts supported on CNT-BM-U (sample N-doped using urea as nitrogen precursor). Both the textural and the surface chemical properties of the support play an important role in the catalytic performance. Among the catalysts tested, the N-doped carbon nanotubes sample is the best support for this catalytic process, while the supports with high amounts of oxygen-containing surface groups decrease the catalytic performance of the metal phases.

Electrochemical Characterisation of NiII‐Crown‐Type Polyoxometalate‐Doped Polypyrrole Films for the Catalytic Reduction of Bromate in Water

The nickel substituted (Ni4[(P8W48O184)(WO2)]28–, crown type polyoxometalate was electrochemically polymerised with conducting polymer pyrrole for the electrocatalytic reduction of bromate in water. The immobilized films of different thickness were characterised by electrochemical and surface based techniques. The resulting films were found to be extremely stable towards redox switching between the various redox states associated with the incorporated POM. This system was found to effectively electrocatalyse the reduction of bromate in water without the interference of other common anions. The detection limit was found to be 0.2 µm, with a linear region from 0.1 mm up to 2 mm bromate. The resulting POM doped polypyrrole films were found to be highly conductive by AC impedance. Surface characterization of the polymer films was carried out by using X‐ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy.

Creation of Pd/Al2O3 Catalyst by a Spray Process for Fixed Bed Reactors and Its Effective Removal of Aqueous Bromate

Palladium nanoparticles were grown on sub-millimeter activated Al2O3 particle support by spraying H2PdCl4 solution evenly onto the support, followed with a thermal reduction under H2 atmosphere. Compared with its counterpart created by the conventional impregnation method, the Pd/Al2O3 catalyst created by the spray process could enrich the existence of active Pd nanoparticles on the surface of the catalyst support and increase their degree of dispersion, resulting in a much higher activity in the catalytic reduction of bromate in water. The effect of Al2O3 support particle size on the bromate removal rate was also investigated, which demonstrated that smaller support particle size could have higher activity in the catalytic reduction of bromate in water because of its larger exposed surface. This Pd/Al2O3 catalyst could be easily used in the fixed bed reactor due to its large support size and demonstrated excellent stability in the catalytic reduction of bromate in mineral water. This Pd/Al2O3 catalyst also exhibited a good catalytic reduction performance on azo dyes as demonstrated by its effective catalytic hydrogenation of methyl orange. Thus, catalysts prepared by the spray method developed in this work could have the potential to be used in fixed bed reactors for various water treatment practices.

Bromate reduction in water promoted by metal catalysts prepared over faujasite zeolite

Bromate reduction in water has been investigated by using mono and bimetallic catalysts prepared over a faujasite zeolite in a semi-batch reactor under hydrogen at room temperature and atmospheric pressure. The structural synthetic analogue Y of the faujasite zeolite in the sodium form, with different particle sizes (NaY, 700nm and nanoNaY, 150nm), was chosen for the preparation of metal catalysts. Ion exchange and incipient wetness impregnation methods were applied to incorporate copper, palladium, rhodium and/or thorium into the faujasite zeolite. Several analytical techniques were used to characterize structural modifications in the metal catalysts and confirm that the metals were successfully trapped in the faujasite structure. The catalytic results demonstrated the importance of the chemical nature of the metals, of the amount of the second incorporated metal, as well as the method used for catalyst preparation. All the metal catalysts showed remarkable performance in the bromate reduction in water, with the bimetallic catalysts presenting the best results, particularly the CuPd pair prepared by the ion exchange method.

Efficient reduction of bromate in water by nano-iron hydroxide impregnated granular activated carbon (Fe-GAC)

Nano-iron hydroxide impregnated granular activated carbon (Fe-GAC) was prepared and tested for reduction of bromate in water. SEM, BET and FTIR characterization of Fe-GAC revealed that nanoscale iron hydroxide (FeOOH) particles with SO42− attached were evenly distributed on the surface of GAC. Fe-GAC can effectively remove bromate in water through firstly adsorption then reduction. The nano-iron hydroxides on GAC enhanced bromate removal rate and the equilibrium bromate adsorption capacity. More FeOOH of Fe-GAC favored the reduction of bromate. Bromate reduction by Fe-GAC was the main mechanism for bromate removal. Fe-GAC performed well through a broad pH range (2–10) with the optimal pH 6–8 for bromate reduction. According to XPS analysis, Fe(III) of Fe-GAC was reduced to Fe(II) during the bromate reduction to bromide. Fe(III)/Fe(II) acted as a catalyst and accelerated the bromate reduction rate by carbon of GAC. The four inorganic anions (SO42−, Cl−, CO33− or PO43−) all exhibited inhibiting effects on bromate removal by Fe-GAC with the following order: PO43−>CO33−>Cl−>SO42−. In all, Fe-GAC is a promising material for efficient reduction of bromate in water.

Bimetallic activated carbon supported catalysts for the hydrogen reduction of bromate in water

The association of bromate in drinking water with several public health risks, namely related to its carcinogenic potential and its toxic nature, has led to an interest in the development of sustainable alternatives for its removal from water. The hydrogen reduction of bromate over supported heterogeneous metallic catalysts has already been shown to be an interesting alternative for the reduction of bromate into less hazardous species, without formation of additional sludges.In this work, the coupling of a noble metal with a second metal supported on activated carbon has been studied for this reaction. Several metals were used for this goal, resulting in a wide array of combinations of noble and promoter metals. All the combinations showed remarkable activity for the complete conversion of bromate into bromide, without accumulation of by-products.The role played by the second metal was extensively studied, for which experiments were conducted using physical mixtures of the corresponding monometallic catalysts and also different metal amounts on the supported bimetallic catalysts. In most cases, the presence of a second metal hindered the activity of the noble metal, when compared with the respective monometallic catalyst. In the case of the Pd–Cu bimetallic catalyst, it is possible to improve the activity obtained with the Pd catalyst. The activity of the bimetallic catalyst was shown to be dependent on the composition.

Bromate reduction in water by catalytic hydrogenation using metal–organic frameworks and sodium borohydride

Catalytic hydrogenation of bromate is a promising approach to remove bromate from water considering that this approach not only removes bromate but also converts it to bromide.

Metal assessment for the catalytic reduction of bromate in water under hydrogen

The presence of bromate ion in water and wastewater is a known problem due to its carcinogenic potential, and other toxic effects on human health. The catalytic reduction under hydrogen is an attractive process for its removal by conversion into bromide ion.Different metals (Pd, Pt, Ir, Rh, Ru, Fe, Sn, Cu, Zu and Ni) supported on activated carbon were assessed for the catalytic reduction of bromate under hydrogen at room temperature and pressure. All these catalysts are active in the conversion of bromate into bromide. Ruthenium, palladium, platinum and rhodium were shown to be the most efficient metals. When the available metal surface for reaction was considered, platinum showed the best activity. The trend of activities was associated to (and discussed on the basis of) the dissociative chemisorption energy of hydrogen over the metals.A mechanism for the reduction of bromate was proposed, involving reactions in the liquid phase, on the surface of the activated carbon support, and on the surface of the supported metal particles. It is proposed that the reaction mechanism on the surface of the metal catalysts comprises the decomposition of hydrogen and subsequent reaction with bromate. This reaction leads to the release of bromide ion and water. The oxidized metal is then reduced by hydrogen, thus closing the catalytic cycle.

Bromate reduction by ultraviolet light irradiation using medium pressure lamp

Bromate reduction in water by ultraviolet irradiation using medium-pressure lamps (UV-M) emitting light in the range of 200–600 nm has been investigated. Effects of certain experimental parameters including the initial bromate concentration, UV light intensity, initial pH, and presence of dissolved organic and inorganic carbon and nitrate on the kinetics and efficiency of UV irradiation for bromate reduction were evaluated. Experimental results showed that UV-M irradiation achieved complete destruction of bromate and almost total conversion of bromate into bromide for the initial bromate concentrations ranging from 10 to 1000 μg/L under different pH conditions. A simple kinetic model for bromate destruction was developed. Bromate decay with time during UV-M irradiation follows pseudo-first-order kinetics. The observed rate constant (kobs) decreased with increasing bromate concentrations upto 100 μg/L and then it becomes constant at 0.058 min−1 for higher bromate concentrations. Increasing the UV light intensity resulted in the increase of the rate of bromate destruction. The kobs increased linearly with increasing light intensity. A UV dose of 1000 mJ/cm2 was sufficient to reduce the bromate concentration to less than 10 μg/L within 10 min. The presence of dissolved organic carbon or carbonate/bicarbonate slowed the bromate reduction rate due to absorption of non-negligible fraction of UV light by these compounds. Presence of nitrate affects both the kinetics and efficiency of bromate reduction.

Reduction of Bromate in Water using Zerovalent Cobalt 2,6-Pyridine Dicarboxylic Acid Crosslinked Chitosan Nanocomposite

Zerovalent cobalt 2,6-Pyridinedicarboxylic acid crosslinked chitosan (ZVCo-PDCA-CHIT) nanocomposite, which was obtained by chemical reduction of cobalt (II) ion chelated nanocomposite with NaBH4, was tested for bromate reduction in water. 2,6-pyridinedicarboxylic acid (PDCA) was used for intramolecular crosslinking of the chitosan linear chains. The products were characterized by FT-IR, XRD and SEM. The FT-IR analyses revealed the presence of coordinating –NH2 and –OH functional groups in chitosan while crosslinked chitosan showed –COOH absorption peaks. The XRD spectrum revealed a typical fingerprint of semi-crystalline chitosan which disappeared in crosslinked chitosan due to disruption of the interpolymer bonds. SEM image revealed a smooth surface for the Chitosan while large pores were observed for the PDCAcrosslinked Chitosan (PDCA-CHIT). ZVCo-PDCA-CHIT nanocomposite showed significant morphological changes with the surface structure being smooth with the disappearance of the holes observed in the crosslinked chitosan structure, indicating a very strong binding of cobalt with most of the functional groups. The applied ZVCo-PDCA-CHIT nanocomposite reduced bromate ions to bromide with possible adsorption onto the nanocomposite. The result showed that bromate reduction in water was significantly higher and near completion under 1 h using ZVCo-PDCA-CHIT (99 ± 1.1%) as compared to PDCAcrosslinked Chitosan (65 ± 1.47%) and Chitosan (53 ± 0.25%).

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.