Removal Efficiency Of Bromate Research Articles

Constructing ultralow-loading Cu single atoms/Fe2O3 particles on Nb2C MXenes for efficient utilization of atomic H to boost electrochemical debromination

Bromate is a commonly identified carcinogenic and genotoxic disinfection byproduct in water. Electrochemical debromination is an environmentally friendly and effective approach but it often suffers the limited reducing atomic H (H*) ability and high metal catalyst dosage. In this study, a unique composite catalyst comprised of ultra-low loading Cu single atoms (0.016 wt%) and Fe2O3 nanoparticles supported on a Nb2C MXene (denoted as Cu0.2/Fe0.1/Nb2C) was synthesized by one-step high-temperature molten salt method. The Cu0.2/Fe0.1/Nb2C significantly outperformed the Nb2C, Cu0.2/Nb2C and Fe0.1/Nb2C counterparts in the electrochemical debromination with a 94.2 % removal efficiency of bromate. It is revealed that the introducing of Cu single atoms, efficiently promotes the adsorption of H* and inhibition of competitive H2 evolution. The incorporation of Fe2O3 nanoparticles significantly increased the electronic metal-support interaction effect between the metal components and Nb2C, thereby forming a noticeable electronic cloud bridge to facilitate efficient charge transfer. Ultimately, the synergistic interplay between Cu single atoms and Fe2O3 nanoparticles plays a crucial role in achieving the remarkable removal performance of bromate. This work not only presents a significant instance of a synergistic catalyst involving metal single atoms and metal nanoparticles for effective electrochemical debromination but also advances the understanding of the electronic metal-support interaction.

Efficient Removal Of Bromate From Aqueous Solution Through Electrocoagualtion Using Aluminum Electrodes

In this study the removal efficiency of bromate from aqueous solution using the electrocoagulation process was investigated. The effects of operational parameters such as initial pH, initial bromate concentration, current density, type electrode, salt concentration, and temperature on the removal efficiency have been studied. With an initial pH of 3.7, an initial bromate concentration of 100 mg/L, (current density 22.7 mA/cm2 using Al electrodes, salt concentration of 1.5 g/L NaCl and temperature of 25° C, The results showed that the removal percentage for bromate was 97% using Al/Al electrodes at 10 min. It can be concluded that electrocoagulation process by Al electrode is very efficient and clean process for bromate removal from Aqueous solution.

Synergistic effects boost electrocatalytic reduction of bromate on supported bimetallic Ru-Cu catalyst

Bromate is a commonly identified carcinogenic and genotoxic disinfection byproduct in water. In the present work, bimetallic Ru-Cu catalyst supported on carbon nanotube (RuCu/CNT) was prepared and the structural properties of the catalysts were characterized. The results show that the presence of Ru enhances the dispersion and reduction of Cu particles in the RuCu/CNT catalyst in comparison with the monometallic Cu catalyst supported on CNT (Cu/CNT). For electrocatalytic reaction on Cu/CNT, bromate is reduced on metallic Cu surface via a redox process. For Ru/CNT, highly active H* radicals are generated on metallic Ru surface via the Volmer process and are used for bromate reduction. As for the RuCu/CNT, bromate is reduced through two main pathways, including direct redox reaction on metallic Cu and indirect reduction by active H* radicals on Ru surface. Accordingly, RuCu/CNT exhibits the highest catalytic activity, ascribed to the synergistic effect between metallic Ru and Cu. Furthermore, the bimetallic catalyst displays much higher catalytic efficiency as compared with previously reported results. The pH, initial bromate concentration, in-situ electrochemical reduction of the electrodes and working potential have strong impacts on the removal efficiency of bromate on RuCu/CNT.

Ultrasound process-enhanced removal of the toxic disinfection by-product bromate from water by aluminum: A comparative study.

As bromate removal and reduction can be also achieved using metals, aluminum (Al) appears as the most promising one for reduction of bromate because Al is abundant element and exhibits a high reduction power. Reactions between bromate and Al shall be even enhanced through ultrasound (US) process because US can facilitate mass transfer on liquid/solid interfaces and clean surfaces via generating microscale turbulence to facilitate reactions. Therefore, the aim of this study is for the first time to investigate the effect of US on bromate removal by Al metal. Specifically, Al particle would be treated by HCl to afford HCl-treated Al (HCTAL), which is capable of removing bromate and even reducing it to bromide. Such a mechanism is also validated by density function theory calculation through determining adsorption energy as -152.8kJ/mole, and oxygen atoms of bromate would be extracted and reacted with Al atoms, releasing bromide ion. US not only facilitated bromate removal by further increasing removal capacity under the acidic condition but also suppressed the inhibitive effect from basicity at relatively high pH. The spent HCTAL could still remove bromate and convert it to bromide after regeneration. These features indicate that US considerably enhances bromate removal by Al. PRACTITIONER POINTS: Bromate removed by Al is elucidated by DFT calculation with Eabsorption = -152.8kJ/mole. Oxygen atoms of bromate are extracted and reacted with Al atoms, releasing bromide ion. A higher power of ultrasound would substantially enhance bromate removal efficiency. Ultrasound also suppresses the inhibitive effect from basicity at relatively high pH. With ultrasound, the interference of co-existing anions on bromate removal is lessened.

Construction of the micro-electrolysis system by Fe0 and clay-carbon derived from oil refining for the removal of ozone disinfection by-products

In this work, the construction of iron-cetyltrimethylammonium chloride modified spent bleaching earth carbon (Fe/CTAC-SBE@C) micro-electrolysis system was first proposed for bromate removal in water. The effects of system parameters including Fe to CTAC-SBE@C mass ratio, CTAC concentration, total dosage, temperature, initial pH and reaction atmosphere were studied. Bromate removal efficiency increased with the decrease of Fe/SBE@C mass ratio from 4/1–3/1, and the further decrease of the mass ratio (from 3/1–1/4) led to the decrease of bromate removal efficiency. CTAC modification could provide the active electron transport paths (SBE@C-CTAC+-BrO3-) theoretically for bromate improved removal, and the optimal CTAC concentration was 25 mmol/L. It was found that pH was a key factor of micro-electrolysis reaction, and bromate removal decreased with the increase of pH, while the removal under neutral (pH=7) and basic (pH=9) conditions still could reach more than 75%. Surprisingly, the coexisting of Cl-, SO42- and NO3- as the electrolytes could penetrate the passivated films on the surface of iron and promote bromate removal; air atmosphere was more favorable to bromate removal than nitrogen atmosphere. In addition, based on product determination and characterization data, the removal mechanism of bromate mainly included CTAC-SBE@C adsorption and electrochemical reduction.

Detection of bromate in packaged drinking water and its removal using polyelectrolyte multilayer membranes

AbstractThe use of bottled water is increasing every day even after the reported presence of microbial and other contaminants. The present study analyzed bromate in bottled water samples collected from four major cities in Kerala, India. It was found that about 40% of the samples contain bromate with a maximum concentration of 9.68 μg/L with an average of 1.56 μg/L. The study also includes the development of a multilayer membrane for the removal of bromate from water. Bilayers of quaternary chitosan salt (QCS)/sodium polystyrene sulfonate (PSS) were deposited on polyethersulfone (PES) microfiltration membrane and which are employed for bromate removal studies. Deposition of six bilayers of QCS/PSS increased the rejection efficiency from ∼4% to ∼84%. The influence of different fabrication and feed parameters on bromate removal efficiency was also studied. Six bilayers of QCS/PSS deposited at pH 2 with 0.5 M NaCl were found to be effective in removing > 90% of bromate from marketed bottled water samples with low energy expense. This study is recommended to implement such a multilayer system as a polishing step in the final stage of water purification in bottling plants to avoid possible contamination and toxicity of bromate in bottled water users.

One-pot synthesis of magnetic algal carbon/sulfidated nanoscale zerovalent iron composites for removal of bromated disinfection by-product

Magnetic algal carbon supported flower-like sulfidated nanoscale zerovalent iron (S-nZVI/AC) composite was firstly synthesized through one-pot method and used for removing bromate. More than 98% of bromate was efficiently removed within 48 min. Compared with the individual S-nZVI treatment, the removal rate constant of the S-nZVI/AC composite treatment was almost doubled. The removal rate constant of bromate increased three times when the S/Fe ratio increased from 0 to 0.3. According to the synergistic effect between the algal carbon and S-nZVI on the bromate removal, the introduction of carbon and sulfide-modification of nZVI were efficient modification approaches for enhancing the removal of bromated using S-nZVI/AC composite. The removal efficiency of bromate increased sharply to more than 98% when the composite dose increased from 0 to 40 mg L−1. The removal rate constant increased linearly from 0.08 to 0.31 min−1 when the initial concentration increased from 50 to 200 μg L−1. The removal efficiency of the bromate still maintained at high level (>85%) after 5 recycles of the S-nZVI/AC composite. Bromate was readily removed under neutral or slight acidic conditions. The bromate removal rate constant increased from 0.10 to 0.27 min−1 when the temperature increased from 15 to 35 °C. The bromate removal rate constant increased almost 4 times when the ionic strength increased from 0 to 3 g L−1. This study demonstrates that S-nZVI/AC composite synthesized through one-pot method is a promising water purification material for efficient removal of bromated disinfection by-product.

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.

Influence of parameters on the photocatalytic bromate removal by F-graphene-TiO2

ABSTRACT Batch experiments of photocatalytic bromate removal by F-Graphene-TiO2 (FGT) were conducted under different reaction conditions. The dosage of FGT, initial bromate concentration, pH, water temperature, and the coexisting substances including common halogen anions, oxyacid ion and humic acid factors affecting the efficiencies of bromate reduction were systematically discussed. Increasing the temperature or the dosage of FGT increased the bromate removal efficiency. The efficiency of bromate reduction was significantly increased by decreasing the pH from 6 to 5, because the isoelectric point of FGT samples was found at a pH of approximately 6.0. The coexisting anions, such as chloride ion, bromide ion, nitrate, chlorate and sulfate, had modest inhibitory effects on bromate removal under the experimental conditions, and the inhibitory effect from fluoride ion was relatively larger. These observations indicate that bromate reduction by FGT is a surface-mediated process, the competitive consumption of photogenerated electrons and the competitive adsorption by coexisting anions on FGT samples probably lead to the decreasing of bromate reduction efficiency. And the increase of appropriate dosage can partly eliminate the influence of coexisting ions. Over 90% of 100 μg/L bromate could be removed with a 0.05 g/L dosage of F1.0G0.1T in 15 min under UV irradiation at intensity of 26 μW/cm2 and pH of 5.2. Moreover, the specific roles of photogenerated electron–hole pairs and the mechanism of photocatalytic bromate reduction were also discussed. These findings suggest that photocatalytic bromate removal by FGT/UV can be a promising method for bromate from water.

Biological Bromate Reduction Driven by Methane in a Membrane Biofilm Reactor

As a potent greenhouse gas with a greenhouse warming potential 28 times that of carbon dioxide over a time scale of 100 years, methane has been proven to be useful as an electron donor for the removal of various contaminants, e.g., nitrate, nitrite, perchlorate, and chromate, from contaminated water. However, microbial bromate reduction supported by methane has not been reported so far. Here, a lab-scale membrane biofilm reactor (MBfR) was set up to explore the feasibility of bromate reduction driven by methane under oxygen-limiting conditions. Long-term operational performance demonstrated that a complete reduction of bromate (BrO3–) to bromide (Br–) could be achieved, with 100% bromate removal efficiency under a volume loading of 1 mg of Br L–1 day–1. Volatile fatty acids (VFAs) were produced in the reactor (concentrations ranging from 1.81 to 27.9 mg/L) under oxygen-limiting conditions. High-throughput 16S rRNA gene sequencing indicated that Methanosarcina became the only dominate methane-oxidizing mic...

Removal efficiency and economic cost comparison of hydrated electron-mediated reductive pathways for treatment of bromate

Bromate, a potential carcinogen, is a well known highly persistent and environmentally recalcitrant contaminant. UV-254/sulfite-based advanced reductive pathways (ARPs) were proposed to eliminate bromate successfully from water. Experiments with N2, N2O, 2-chlorophenol, inorganic ions, and different pH (highly acidic to highly basic) proved that UV-254/sulfite successfully provides aqueous electron that effectively participate in bromate removal from water. Significant removal, 86%, of initially 39.0µM bromate was achieved by UV-254/sulfite under conditions that dominate aqueous electron based pathways. The high second-order rate constant of 5.3×109M−1s−1 determined proved high reactivity of aqueous electron with bromate. The kinetic and removal efficiency of bromate showed linear relationship with the rate of aqueous electron formation. An increase in kinetic and removal efficiency of bromate was observed with increasing initial sulfite concentration and decreasing bromate concentration. The impacts of different initial concentrations of the typical ions commonly found in water were studied in detail to extend the UV-254/sulfite-based process for potential practical applications. The lower molar absorptivity of bromate at 254nm determined proved insignificant removal of bromate under direct photolysis. The impacts of initial sulfite concentration on removal of bromate in UV-254/sulfite-based process also minimized role of direct photolysis. The cost evaluation and rapid decomposition of bromate into bromide proved UV-254/sulfite-based ARPs to be economical and highly rewarding in efficient decomposition of bromate and other inorganic oxyhalides.

UV treatment for the removal of bromate formed during ozonation of groundwater. Influence of the oxidation process on the removal efficiency

The presence of bromide ions in waters treated with ozone can lead to bromate ions and brominated compounds formation, potentially carcinogenic. This poses a need to remove the bromates through other treatment, as UV. In this work the effects of the water composition, and the corresponding variation due to oxidation, on the UV efficiency for the reduction of bromate to bromide ions in groundwater (GW) were investigated. For this purpose an experimental apparatus was specifically designed and experimental tests with ozone and with a UV lamp 6W were performed. The experimental results show that the reduction of the bromates to bromides by UV is max 41% in GW, depending on ozone dose and initial bromate concentration. The experimental data were fitted with a first order model and the kinetic constant determined. The effects of the ozone and UV treatment on others groundwater components, as TOC and inorganic nitrogen, were taken into account and the corresponding influence on the bromate removal efficiency was evaluated. To this aim, comparative tests with UV in purified water (PW) (reagent grade) and GW spiked with controlled amount of bromates were performed. It was verified that the removal efficiency of bromate by UV increases with increasing of ammonia concentration, but decreases with increasing of TOC and when intermediate bromide species, produced by ozonation, are presents.

Reduction of bromate from water by zero-valent iron immobilized on functional polypropylene fiber

The highly reactive micro-sized zero-valent iron (mZVI) immobilized in acrylic acid (AA) functionalized polypropylene fiber (PP-g-AA) was successfully prepared, and used for the bromate removal from solution. The PP-g-AA was used as a novel carrier for its high strength and continuous supports with chelating functional groups. The mZVI was immobilized firmly on PP-g-AA via complexation and liquid phase reduction, which prevented the aggregation of mZVI and release of Fe ions. The mZVI/PP-g-AA was characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and emission scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) surface area analyzer. Due to the coordination with carboxyl groups, the mZVI presented excellent distribution and high activity for reduction of bromate. Meanwhile, the bromate removal efficiency affected by initial bromate concentration, pH, common anions and humic acid (HA) were respectively evaluated. The effects of pH value on bromate reduction was slight. It was related to the buffering performance of the COOH/COO− groups around the areas where the reduction took place. The inhibitory effects of common anions and HA were slight and negligible. In this study, the concentration of Fe2+/3+ in solution was low (<19.0μg/L) and kept constant during reduction process. On account of the coordination of carboxyl groups on the functional PP fibers, Fe2+/3+ could be remained in the carrier and not be released into solution.

Multiparameter optimization of bromate sorption on anion exchange resin by a two-step statistical strategy: Plackett–Burman and Box–Behnken experimental design

Bromate, an anion with carcinogenic properties, may be formed during ozonation or chlorination of water containing bromide. Previous research has shown that the trace levels of bromate in solution could be effectively removed by macroporous Cl-type anion exchange (D201-Cl) resin. In the present study, this multiparameter sorption process was optimized by a two-step statistical experiment design. Firstly, the Plackett–Burman (P–B) design was employed to evaluate the effect of sorption parameters. Sorbent dosage, coexisting anion concentration, and initial pH had a significant impact on bromate removal, and these variables were further optimized using a Box–Behnken design (BBD). The maximum removal efficiency of bromate (90.67%) was achieved under the optimal conditions of sorbent dosage 1.08 g/L, coexisting anion conc. 15.55 mg/L, and pH 8.93. The experimental results were in good agreement with the predicted values, indicating that the integrated P–B and BBD design is a powerful and effective approach for the statistical optimization of bromate sorption process.

Effect of Fe loading quantity on reduction reactivity of nano zero-valent iron supported on chelating resin

In this study, nanoscale zero-valent iron (NZVI) were immobilized within a chelating resin (DOW 3N). To investigate the effect of Fe loading on NZVI reactivity, three NZVI-resin composites with different Fe loading were obtained by preparing Fe(III) solution in 0, 30 and 70% (v/v) ethanol aqueous, respectively; the bromate was used as a model contaminant. TEM reveals that increasing the Fe loading resulted in much larger size and poor dispersion of nanoscale iron particles. The results indicated that the removal efficiency of bromate and the rate constant (Kobs) were decreased with increasing the Fe loading. For the NZVI-resin composite with lower Fe loading, the removal efficiency of bromate declined more significantly with the increase of DO concentrations. Under acidic conditions, decreasing the pH value had the most significant influence on NZVIR3 with highest Fe loading for bromate removal; however, under alkaline conditions, the most significant influence of pH was on NZVI-R1 with lowest Fe loading. The effects of co-existing anions NO3–, PO43– and HCO3– were also investigated. All of the co-existing anions showed the inhibition to bromate reduction.

Adsorption of bromate from emergently polluted raw water using MIEX resin: equilibrium, kinetic, and thermodynamic modeling studies

This study investigated the kinetics, equilibrium, and thermodynamics of bromate adsorbed on magnetic ion-exchange (MIEX) resin by batch experiments. The pseudo-second-order kinetic model could well describe the adsorption process, and the film diffusion controlled the whole adsorption rate. The Langmuir and Redlich–Peterson isotherm models fitted well the equilibrium data. High removal efficiency of bromate was observed at neutral pH. Other coexistent anions present in raw water affected negatively the removal of bromate significantly. The thermodynamic studies showed the adsorption was a spontaneous thermodynamically, endothermic, and entropy driving process. These analyses on the average free energy, activation energy of adsorption, and quantity changes of bromate and chloride ions in solution before and after adsorption demonstrated that the removal mechanism of bromate adsorbed on MIEX resin was an ion-exchange reaction. Results of the findings suggested that MIEX resin could be utilized effectively to remove bromate from emergently polluted raw water.

Ordered mesoporous carbon immobilized nano zero-valent iron in bromate removal from aqueous solution

The present work aims to investigate bromate removal from water with the application of a material nano Fe0/OMC (ordered mesoporous carbon) composite, under various experimental conditions. The effect of temperature, react time, bromate concentration, etc. on bromate removal efficiency was studied. Removal efficiency of bromate by nano Fe0/OMC achieved 96.1% with a contact time of 10min at 298K. Reduction action dominates the whole process with a little adsorption accompanied, and approximately 90% bromate was restored to bromide. Kinetics models were used to correlate the kinetics experimental data and the kinetics parameters reveal that the kinetics data were well fitted to pseudo-second-order model. The maximum bromate uptake at 298K was found to be 25.9mg/g at the initial bromate concentration 10mg/L, but it changed little with a decrease in temperature. Equilibrium isotherms were analyzed by the Freundlich and Langmuir isotherm models. The data fit favorable to the Langmuir isotherms with high-correlation coefficients (0.941–0.998). The present work shows that the nano Fe0/OMC composite would be a promising material in the study of drinking water purification.

Special Issue on Drinking Water Safety, Security, and Sustainability

Special Issue on Drinking Water Safety, Security, and Sustainability

Sorption of trace levels of bromate by macroporous strong base anion exchange resin: Influencing factors, equilibrium isotherms and thermodynamic studies

Bromate, a cancerigenic disinfection by-product (DBP), has been increasingly concerned in recent years. In this study, macroporous Cl-type strong base anion exchange resin (D201-Cl) was used to remove trace levels of bromate from aqueous solution. Batch sorption experiments were performed to evaluate the influence of various factors such as initial bromate concentration, contact time, solution initial pH and temperature on the uptake of bromate. D201-Cl resin exhibited higher bromate removal efficiency (residual concentration of bromate was under the maximum contaminant level (MCL) of 10μg·L−1 at all conditions investigated) and broader pH scope of application (4.50–9.92). The maximum sorption capacity reached to 105.5mg·g−1 at 298K. The kinetics data were well described by pseudo-first-order kinetic model, and Freundlich isotherm model and Redlich–Peterson isotherm model fitted the sorption isotherms (R2>0.99). Thermodynamic analysis showed that the sorption process was spontaneous and endothermic. In addition, D201-Cl resin still maintained high bromate removal efficiency after regenerated by 0.1M NaCl solution for five cycles. The results indicate that D201-Cl resin is a low-cost and efficient sorbent for bromate removal from drinking water, especially for trace levels of bromate.

Enhanced removal efficiency of bromate from aqueous solutions by nanoscale zero-valent iron immobilized on activated carbon

Nanoscale zero-valent iron (nZVI) immobilized on activated carbon (AC) was synthesized via liquid phase reduction route. The samples were characterized by X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller surface area measurement. The effects of bromate (BrO3- ) removal in water with nZVI/AC samples were evaluated. The results show that nZVI/AC presented superior bromate removal efficiency, which is contributed to its reduction and synergistic adsorption/sedimentation of BrO3-. Iron species in nZVI/AC acted as electron mediator and catalyst during bromate reduction, and bromide was the final reductive product. The dosage of nZVI/AC, solution pH, initial bromate concentration, reaction time, and temperature affected the rates of bromate reduction/adsorption. The optimum pH range of bromate removal is wide enough from 4.0 to 9.0. Bromate removal capacity of nZVI/AC was determined to be approximately 25 mg/g. These findings suggest that bromate removal by nZVI/AC can be an effective method for bromate control.