Bromate Adsorption Research Articles

Efficient and reductive removal of bromate using a novel and stable nanoscale zero-valent iron embedded in N-doped carbon derived from metal-organic frameworks

Nanoscale zero-valent iron (nZVI) has drawn great interest in the remediation of contaminated waters. In this study, we prepared a novel and stable nZVI embedded in N-doped carbon matrix (nZVI@MOF-CN) using a facile direct carbonization method, in which an iron-containing metal-organic framework (MOF) served as both the iron and carbon sources, and melamine as the nitrogen source. The nZVI@MOF-CN composites were used in the removal of bromate in water, which could be effectively reduced by the surface electrons transferred from nZVI to the carbon encapsulation layer due to the Schottky-Mott effect. Doped nitrogen significantly facilitated the reduction of bromate by nZVI, because it enhanced the nZVI dispersion and bromate adsorption, and modulated the carbon matrix conductivity. The bromate reduction activity of nZVI@MOF-CN was more than 50 times higher that of its un-doped counterpart and a commercial nZVI. Moreover, owing to the protection of carbon encapsulation layer, nZVI@MOF-CN exhibited good stability and reusability. The leached concentration of iron ions of nZVI@MOF-CN was less than 5% of the commercial nZVI under the same reaction conditions. Commercial nZVI almost completely lost its bromate reduction activity after use (3% reduction efficiency in the examined time frame), while nZVI@MOF-CN maintained a reduction efficiency of 61%. The nZVI@MOF-CN could be effectively regenerated by hydrogenation reduction. After five reaction-regeneration cycles, nZVI@MOF-CN still achieved a bromate reduction efficiency of approximately 80%. These results suggest that MOF-derived nZVI materials are highly reactive and stable for the reductive removal of pollutants in water.

Optimization of bromate adsorption onto Fe-CNTs nanocomposite using response surface methodology

This study was aimed at employing response surface methodology (RSM) for optimization of process variables and identifying optimal conditions for the adsorption of bromate (BrO3-) from contaminated water using multi-walled carbon nanotubes, based on iron hydr(oxide), Fe-CNTs nanocomposite. Fifteen experimental runs were conducted in batch mode to study the effect of individual as well as interactive process variables, i.e., pH, BrO3− initial concentration, and adsorbent dose, on the removal of BrO3− using Box–Behnken design (BBD) of RSM. The coefficient of determination (R2) at 98.34% indicated a good agreement between actual and predicted values. The main effect and contour plot were drawn to obtain the independent and interactive effect of operational variables on BrO3− uptake. A process optimization curve was drawn to determine the optimum operating conditions that lead to a desirable response. The optimum conditions for BrO3− adsorption using Fe-CNTs nanocomposite were found to be pH 2.0, initial BrO3− concentration of 10.0 mg/L, and adsorbent dose of 0.010 g per 50 mL solution.

Enhanced bromate adsorption by using a-FeOOH pillared bentonite

Enhanced bromate adsorption by using a-FeOOH pillared bentonite

Synergistic adsorption and electrocatalytic reduction of bromate by Pd/N-doped loofah sponge-derived biochar electrode

In this work, a novel Pd/N-doped loofah sponge-derived biochar (Pd/NLSBC) material with three-dimensional (3D) network structure was prepared through the carbonization-impregnation method and applied as cathode for electrocatalytic bromate removal. The N-doped biochar not only increased the adsorption capacity of electrode, but also facilitated electron transfer, subsequently resulting in the high electrocatalytic activity for bromate removal. The results indicated higher bromate adsorption capacity of Pd/NLSBC electrode was favorable to the electrocatalytic bromate removal. The influences of significant operating factors including calcination temperature, initial solution pH, applied current intensity, and initial bromate concentration on electrocatalytic bromate removal were also optimized. Under the current intensity of 10 mA, Pd/NLSBC-800 exhibited the highest bromate removal efficiency (96.7 %) and the bromide conversion rate reached almost 100 % at the initial bromate concentration of 0.781 μmol L−1. This process could be effectively performed over a wide range of pH (2.0–9.0) and be well fitted to the pseudo-first-order kinetic model under different conditions. The reaction mechanism study indicated that both direct electron transfer and indirect reduction by the active hydrogen atom (H*) contributed to the elctrocatalytic bromate removal. Meanwhile, Pd/NLSBC-800 electrode could maintain its high electrocatalytic activity for bromate removal after five cycles.

The study of bromate adsorption onto magnetic ion exchange resin: Optimization using response surface methodology

The purpose of this study is to investigate the adsorption performance of bromate in water with magnetic ion exchange (MIEX) resin. In batch experiments, various factors affecting bromate adsorption are discussed, including initial solution pH and concentration, adsorption time, natural organic matter, coexistent anions, stirring intensity, adsorbent dosage, bed volume and ion strength. In addition, the main factors affecting adsorption efficiency of bromate are studied by the response surface methodology. Kinetic data and the sorption equilibrium agree well with the pseudo-first-order model and Langmuir, respectively. To sum up, bromate adsorption on the MIEX resin involves physical adsorption and chemisorption. In addition, the saturated sodium chloride solution can be used to effectively regenerate the MIEX resin. MIEX resin has strong adsorption capacity for bromate is shown by a series of experiments and characterizations, which lays a foundation for the practical application of water treatment in the future.

Elimination of carcinogenic bromate ions from aqueous environment with 4-vinyl pyridine-g-poly(ethylene terephthalate) fibers.

In this study, poly(ethylene terephthalate) fibers grafted with 4-vinyl pyridine (PET-g-4VP) was synthesized with using a radical polymerization method and its removal capacity for bromate ions in the aqueous solution was explored. The synthesized graft copolymer was structurally characterized by scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR). The effect of some parameters such as pH, grafting rate, processing time, and ion concentration on bromate removal was examined with batch experiments. The sorptions of bromate onto the PET-g-4VP fibers were both verified with FTIR and X-ray fluorescence analysis (XRF) and the remaining amount of bromate after adsorption process was determined with an ion chromatography (Shimadzu). Moreover, kinetic and isotherm studies were also performed for adsorption of bromate with the grafted fibers. The point of zero charge (pHpzc) of the PET-g-4VP fibers was found to be 7.5 and the fibers removed maximum amount of bromate from aqueous solution at pH 3. Equilibrium time of adsorption was determined to be 75 min and the adsorption kinetic was found to be pseudo-second-order model. It was observed that the increase in the amount of grafted 4VP onto the PET fibers increased the bromate removal capacity of the fibers; however, when the grafting yield of 4VP was over 80%, the bromate removal ability of the fibers decreased. The maximum bromate removal capacity of the PET-g-4VP was determined to be 183 mg/g when the initial bromate amount was 800 mg/L, treatment time was 75 min, pH of the solution was 3, and 4VP grafting yield was 80%. When the initial bromate concentration was higher than 800 mg/L, the removal rate of the PET-g-4VP fibers was not changed. In addition, bromate ion adsorption data indicated compliance with the Freundlich isotherm. The adsorbent fibers obtained by this study may be promising candidates for the removal of bromate ions from the aqueous media.

Enhanced performance and mechanism of bromate removal in aqueous solution by ruthenium oxide modified biochar (RuO2/BC)

The removal of pollutants from water using agricultural waste-based biomaterials is gaining extensive attention. In this study, biochar loading ruthenium oxide (RuO2/BC), a novel composite for bromate removal from drinking water, has been prepared by the impregnation method. Based on the single-factor design, a Box-Behnken design (BBD) of the response surface methodology (RSM) was applied to access the mutual interactions and effects between the three factors and optimized preparation conditions (activation time is 3.9 h, activation temperature is 612.2 °C and mass ratio of biochar to RuCl3 is 38.9: 1). The effects of initial solution pH, RuO2/BC dosage and initial bromate concentration on bromate removal by RuO2/BC were investigated. The Field Emission Scanning Electronic Microscopy (FESEM), Brunauer-Emmett-Teller (BET), Energy Dispersive X-Ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Zeta potential were used to characterize the properties of prepared composite. Results showed that bromate removal by RuO2/BC was highly pH dependent and the bromate reduction kinetics followed the pseudo-first-order kinetic model. The detailed mechanism including adsorption and reduction of bromate by the synergistic effect of RuO2 and biochar (CC, CO and OH) was demonstrated. These results proposed a new approach for the remediation of bromate contaminated water.

Effects of pyrolysis temperature on nitrate-nitrogen (NO3−-N) and bromate (BrO3−) adsorption onto date palm biochar

Biochars (BCs) produced through biomass pyrolysis are highly efficient adsorbents for retaining dissolved cations in soil and water. However, their anionic sorption characteristics are unclear and depend on the feedstock used and the pyrolysis temperature. Herein, the adsorption of nitrate-nitrogen (NO3−-N) and bromate (BrO3−) anions onto date palm biochar was evaluated by considering the pyrolysis temperature in relation with the initial concentrations, initial pH, and adsorbent dose. Biochars from date palm rachis were produced at 300 °C (BC300) and 700 °C (BC700). The latter exhibited the highest adsorption efficiency of NO3−-N from aqueous solutions at an initial pH of 2, which was 25.8%–44.3% (at an adsorbent dose of 4 g L−1) and 47.0%–73.0% (at an adsorbent dose of 10 g L−1). In contrast, BC300 adsorbed BrO3− with an adsorption efficiency of 19.3%, 14.5%, 14.9%, and 13.6% at initial added concentrations of 5, 10, 15, and 20 μg L−1, respectively. However, BC700 showed zero adsorption for BrO3−. The results also showed that the non-linear models of Langmuir and/or Freundlich for NO3−-N and BrO3− adsorption described the adsorption data better in most cases. It could be concluded that high pyrolysis temperature BC are suitable for adsorbing NO3−-N, and low pyrolysis temperature BC may be used to adsorb BrO3−.

Highly effective bromate reduction by liquid phase catalytic hydrogenation over Pd catalysts supported on core-shell structured magnetites: Impact of shell properties

Liquid phase catalytic reduction of bromate with supported noble metals as the catalysts is a promising method to remove bromate in water. Magnetic supports provide a feasible way to recover catalysts whose surface properties also strongly influence the catalytic efficiency. In this study, Pd nanoparticles supported on core-shell structured magnetites with varied shells (e.g., carbon, SiO2, polypyrrole, polyaniline, polydopamine and chitosan) were prepared and catalytic reduction of bromate on the catalysts was investigated. The results showed that in comparison with other catalysts Pd/(Fe3O4@polyaniline) exhibited a higher catalytic efficiency due to its higher point of zero charge and surface hydrophilicity. In parallel, bromate reduction on Pd/(Fe3O4@polyaniline) followed the Langmuir-Hinshelwood model, confirming the crucial role of bromate adsorption. At pH 5.6 and a catalyst dosage of 0.05 g/L, 0.4 mM bromate could be completely reduced into bromide within 120 min. Furthermore, the magnetic catalysts could be effectively separated and recovered under an external magnetic field within 3 min. The results of catalyst reuse showed that after five consecutive catalytic reduction cycles Pd/(Fe3O4@polyaniline) retained 87% of its fresh catalyst activity. The present findings indicate that Pd/(Fe3O4@polyaniline) with polyaniline as the shell is a highly active, stable and recyclable catalyst for liquid phase catalytic hydrogenation of pollutants in water.

Elimination of bromate from water using aluminum beverage cans via catalytic reduction and adsorption

While zero valent aluminum (ZVAl) is a promising reductant for eliminating bromate from water, ZVAl is typically obtained from reagent grade aluminum. As used aluminum beverage can is the most common aluminum waste, it can be conveniently used to prepare ZVAl. Thus, in this study aluminum beverage cans are employed for the first time as a plentiful and easily accessible aluminum source to afford ZVAl for eliminating bromate from water. As aluminum is easily oxidized to form aluminum oxide, aluminum can pieces (ACPs) are pre-treated with HCl for removing the oxide layer to afford ZVAl. While non-acid-treated ACP is ineffective to remove bromate, the acid-treated ACP successfully eliminates bromate from water completely. Bromate elimination by ACP is attributed to reduction of bromate to bromide by the reactive sites of ACP and adsorption of bromate to the surface of ACP. Bromate elimination by ACP also proceeds much faster at higher temperatures and low pH values, while the alkaline condition causes serious negative effects on bromate elimination. Besides, oxalic acid is found to facilitate bromate elimination not only on the kinetics but also reduction to bromide because the passivation layer is suppressed in the presence of oxalic acid. ACP could also be reused and the acid-washing regeneration could enable used ACP to restore its reactive sites for bromate elimination. This study successfully demonstrates the valorization of aluminum beverage cans for mitigating the toxic bromate and the findings here provide useful information and insights to develop aluminum beverage cans for controlling pollutants in water.

β-FeOOH-Coupled Activated Carbon Prepared by the High Temperature Impregnation Method for Bromate Removal from Water

β-FeOOH-coupled activated carbon (FAC) was prepared and used to remove bromate from an aqueous phase. SEM, XRD, and FTIR analyses indicated that a larger number of β-FeOOH particles were anchored on the AC surface, which greatly enhanced the bromate adsorption and reduction rates. The influences of the pH, contact time, temperature, and competitive anions on bromate removal by FAC were evaluated. FAC can be used over a wide pH range (3–8) for bromate adsorption and reduction, and competing anions inhibit bromate uptake. The adsorption kinetics agreed well with the pseudo-second-order model (R2 ≥ 0.99), and the adsorption isotherms were well fitted by the Langmuir model. The thermodynamic analysis suggested that bromate removal by FAC was a spontaneous and endothermic process. Bromate was adsorbed and then reduced to bromide; Fe3+ acted as a catalyst to accelerate the reductive reaction. The results of this study indicate that FAC is a stable and promising material for bromate removal.

High removal performance of a magnetic FPA90-Cl anion resin for bromate and coexisting precursors: kinetics, thermodynamics, and equilibrium studies

In this study, the FPA90-Cl resin was magnetized with supported Fe3O4 particles using a chemical co-precipitation method and its removal performance of bromate and coexisting precursors was explored. The magnetized FPA90-Cl resin was structurally characterized by SEM, FT-IR, and XRD. The effects of the initial concentrations, temperature, and resin dosage on bromate and bromide ion removal in drinking water were investigated using batch experiments. The magnetized FPA90-Cl resin exhibited a high removal efficiency for bromate and bromide ions at three initial concentrations, and the residual bromate concentrations were under the maximum contaminant level (MCL) of 10μgL-1 after 80min. The adsorption data of bromate and bromide ion could be well described by a pseudo-first-order kinetic model (R2˃0.98). The bromate removal alone was further studied by varying the initial solution pH, temperature, and competitive anions. The results showed that the magnetized FPA90-Cl resin could be used over a wide pH range (4.0-9.0). The maximum sorption capacity of the magnetized FPA90-Cl resin for bromate reached 132.83mgg-1 at 298K. The Freundlich and Redlich-Peterson isotherm models fit the bromate adsorption equilibrium better (R2˃0.99) than the Langmuir isotherm model (R2˃0.98). The thermodynamic analysis showed that the bromate adsorption process was endothermic. The negative ΔG and positive ΔS indicated that the process was spontaneous and that randomness increased after adsorption, respectively. The competition of coexisting anions with bromate was in the order of SO42-> CO32-> Cl-> NO3-> HCO3-> PO43-. Additionally, the magnetized FPA90-Cl resin could maintain a high bromate and bromide ion adsorption capacity after five cycles of regeneration by a 0.1M NaCl solution. Graphical abstract ᅟ.

Thiol-functionalized metal-organic framework for highly efficient removal of bromate from water

Metal-organic frameworks (MOFs) named HKUST-1 ([Cu3(BTC)2(H2O)3]n, BTC = benzene-1,3,5-tricarboxylate) were functionalized by thiol groups through a facile coordination-based postsynthetic strategy (HKUST-1-SH). HKUST-1-SH was explored as a novel adsorbent for efficient removal of bromate. HKUST-1-SH showed a remarkable adsorption capacity of 59.6 mg g−1, approximately 5-times higher than that of HKUST-1. The bromate adsorption process of isotherms, kinetics, the effects of pH value and co-existing ions were examined, and the adsorption mechanism was also studied. The results showed the adsorption process fits the Langmuir adsorption model, and the pseudo-second-order model described the kinetics well. HKUST-1-SH works effectively for removal of bromate in a wide pH range (3–10), and in the presence of other substances such as sulfate, bromide and nitrate. The production of bromide in solution and the detection of SO3H groups from FT-IR spectra indicate that the main mechanism of HKUST-1-SH for bromate removal is redox reaction. The work opens up a new way for bromate removal in water.

Enhanced adsorption of bromate from aqueous solutions on ordered mesoporous Mg-Al layered double hydroxides (LDHs)

An ordered mesoporous Mg-Al layered double hydroxide (meso-LDH350) with a fairly high Brunauer-Emmett-Teller (BET) surface area (126m2g−1) has been facilely synthesized and then evaluated for the adsorptive removal of bromate from aqueous solutions. Adsorbents were characterized by a variety of techniques (e.g., XRD, FTIR, SEM, TG-DSC, N2 physisorption, XPS, etc.). The adsorption studies indicated that the presence of background electrolytes and competitive anions can obviously repress the uptake of bromate on LDHs. The adsorption isotherms agree well with the Langmuir model, giving a maximum adsorption capacity of 59.34mgg−1 (pH 7.5, 10°C) for meso-LDH350, which is much higher than other LDH-type adsorbents reported in literature. The adsorption kinetic data can be well fitted with the pseudo-second-order rate model. Based on the macroscopic and microscopic studies, bromate adsorption on meso-LDH350 was associated with two mechanisms: the reconstruction of the layered structures of meso-LDH350 and the anion-exchange between bromate and the intercalated anions.

Chemically modified chitosan polymers for bromate removal

Bromate is a harmful byproduct formed during drinking water disinfection processes. In this work, adsorption of bromate by natural chitosan and its chemically modified polymers has been investigated. Bromate adsorption was found between 22.73 mg/g and 43.48 mg/g. Adsorbents were analysed by Fourier transform infrared-ATR spectroscopy. It is suggested that chemical adsorption is the main bromate adsorption mechanism. By fitting theoretical results to experimental data, it is shown that the Langmuir adsorption model and the second-order kinetic model are more applicable to explain the adsorption process. Furthermore, increased bromate adsorption is found at high temperature and at low pH, while coexisting ions have little influence at low concentrations.

Enhanced Electroreductive Removal of Bromate by a Supported Pd-In Bimetallic Catalyst: Kinetics and Mechanism Investigation.

In this work, the electroreductive removal of bromate by a Pd1-In4/Al2O3 catalyst in a three-dimensional electrochemical reactor was investigated. A total of 96.4% of bromate could be efficiently reduced and completely converted into bromide within 30 min under optimized conditions. On the basis of the characterization results and kinetics analysis, a synergistic effect of Pd and In was observed, and Pd1-In4/Al2O3 had the highest reaction rate constant of 0.1275 min-1 (vs 0.0413, 0.0328, and 0.0253 min-1 for In/Al2O3, Pd/Al2O3, and Al2O3). The results of electron spin resonance and scavenger experiments confirmed that both direct electron transfer and indirect reduction by atomic H* were involved in the bromate removal process, while the direct reduction played a more important role. Moreover, the introduction of In could increase the zeta potential of Pd1-In4/Al2O3, facilitating bromate adsorption and its subsequent reduction on the catalyst. Finally, a reaction mechanism for bromate reduction by Pd1-In4/Al2O3 was proposed based on all the experimental results.

Adsorptive Bromate Removal from Aqueous Solution by Commercial Strongly Basic Resin Impregnated with Hydrated Ferric Oxide (HFO): Kinetics and Equilibrium Studies

Commercial strongly basic resin D201-Cl was impregnated with hydrous ferric oxide (HFO) in FeCl3–HCl–NaCl solution for absorptive removal of bromate from aqueous solution. The influences of initial bromate concentration, contact time, initial pH, temperature, and competing anions on the uptake of bromate by HFO-impregnated resin D201-Cl (HFO-201) were investigated by batch adsorption experiments. Experimental results showed that the adsorption process could be described by pseudo-first-order kinetics and be divided into three stages according to the intraparticle diffusion parameter. The maximum adsorption potential of HFO-impregnated resin for bromate was 292.81 mg·g–1 at 298 K, which is much greater than those reported in previous studies. The experimental data fitted well to the Redlich–Peterson isotherm model (R2 > 0.99). Thermodynamic parameters such as free energy, enthalpy, and entropy demonstrated that bromate adsorption on HFO-201 was spontaneous and exothermic and occurred by physisorption. Mean...

Bromate removal from water by polypyrrole tailored activated carbon

Bromate adsorption behavior and mechanism were examined on a novel adsorbent devised via depositing polypyrrole (Ppy) into the pores of nut shell-based activated carbon (NAC). This Ppy-tailored activated carbon (Ppy-NAC) hosted positively charged polypyrrole functionality that offered considerable sorption capacity for bromate. Specifically, the Ppy-NAC achieved a bromate loading of 62.5mg/g in the adsorption isotherm, 8.3 times higher than the pristine NAC. The adsorption isotherm data were fitted well by the Langmuir model, and the adsorption kinetics were described well by the pseudo-second-order equation. The occurrence of chloride ions in solution showed that Cl− exchanged with BrO3− during the adsorption process. The X-ray photoelectron spectroscopy (XPS) analysis and the detection of bromide in solution indicated that some of BrO3− were reduced to Br−, and the produced bromide ions were released to the solution and adsorbed on the Ppy-NAC. The increase of oxygen-containing functional groups on Ppy-NAC after adsorption verified that the redox reaction occurred during the adsorption process. The mechanisms of bromate removal by the Ppy-NAC included ion exchange and reduction reaction of bromate on the Ppy-NAC surfaces.

Synthesized of macroporous composite electrode by activated carbon fiber and Mg–Ca–Al (NO3) hydrotalcite-like compounds to remove bromate

Abstract In this study, a novel composite electrode was been modified by using activated carbon fiber (ACF) and Mg–Ca–Al (NO3) hydrotalcite-like compounds by electrophoretic deposition (EPD) method. The resulting electrode was characterized by SEM, BET and cyclic voltammetry (CV). The results indicated the specific surface area of the composite electrode (MACF electrode) is twice as the basic one (ACF electrode) and the MACF electrode revealed a higher capacity of BrO3− ions. The adsorption experiments results showed that the adsorption capacity of electrode increased with the increase of electrical potential and initial bromate concentration. Furthermore, the bromate adsorption of the two electrodes was suppressed by the presence of coexisting anions, wherein the inhibition is ordered as follows: SO42− > CO32− > Cl−. What is more, the modeled results indicated that the adsorption process of bromate by the electrode derived from physical sorption and controlled by the intra-particle diffusion.

Bromate Adsorption on Three Variable Charge Soils: Kinetics and Thermodynamics

A series of batch experiments about adsorption of bromate onto three variable charge soils from Southern China was carried out. The adsorption behavior of bromate was estimated as a function of reaction time (0–240 min), and the concentration of bromate at a fixed value (100 μg/L) at 25, 35, and 45°C. Bromate adsorption increased with the rise of temperature, indicating that bromate adsorption onto the variable charge soils was an endothermic process. The pseudo‐second‐order kinetic equation was used to describe the kinetic data. The adsorption equilibrium time of BrO3– onto three soils was about 120 min and independent of the reaction temperature. The data of isotherm experiments fit well with the Langmuir model, which implied that monolayer adsorption was feasible during the sorption process. The data of the adsorption experiments at different reaction temperatures were used to calculate thermodynamic parameters. The thermodynamic parameters calculated suggest that bromate adsorption onto the variable charge soils from Southern China was a spontaneous, endothermic, and entropy‐driven reaction as well as a physical adsorption process.