Spectrophotometric Determination of Trace Amounts of Vanadium(Ⅴ) by Means of Its Catalytic Effect on Oxidation of Azomethine-H by Bromate

A new selective and sensitive kinetic method for determination of trace amounts of vanadium(Ⅴ) (0.5～40ng/ml) based on its catalytic effect on the oxidation of azomethine H by bromate at pH 4.2 and 25 ℃ was reported and its reaction mechanism was studied.The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation product of azomethine H at 436 nm after a fixed time ( 5 min ).The detection limit of the method is down to 2.0×10 -10 g/ml and the relative standard deviation (RSD) for 30 ng/ml of V(Ⅴ) is 0.26 % ( n =6). The effect of foreign ions on V(Ⅴ) determination was also discussed,and the method is mostly free from interferences of other ions.The proposed method was successfully applied to the determination of trace amounts of vanadium in water samples.

Bromate removal by activated carbon adsorption:material selection and impact factors study

Studies are conducted by using activated carbon process aimed at bromate removal from the raw water.Screening of activated carbon for bromate removal was performed in different activated carbons.GAC Merck possesses the highest iodine number and surface area,the highest number of basic groups and Vmeso,thereby contains the highest adsorption velocity and adsorption capacity.Impact factors of bromate removal on activated carbon were studied.Through static absorption experiments we studied the effect of adsorption time,pH,temperature,anions and organic matter on bromate removal.With the decrease of pH,removal of bromate enhanced,suggests that it may be possible to increase bromate reduction through pH control.The increase of temperature will be favorable to adsorption of bromate on activated carbon.Anions and organic matter can inhibit the adsorption of bromate on activated carbon through competing active sites.Bromate removal can be improved by controlling key water quality parameters.

NEW OSCILLATING REACTIONS CATALYZED BY TETRAMETHYLTETRAAZACYCLOTETRAENE （TIM）NICKEL（Ⅱ）COMPLEX IN BROMATE－PYRUVIC ACID ──SULFURIC ACID SYSTEM

ＮＥＷ ＯＳＣＩＬＬＡＴＩＮＧ ＲＥＡＣＴＩＯＮＳ ＣＡＴＡＬＹＺＥＤ ＢＹ ＴＥＴＲＡＭＥＴＨＹＬＴＥＴＲＡＡＺＡＣＹＣＬＯＴＥＴＲＡＥＮＥ （ＴＩＭ）ＮＩＣＫＥＬ（Ⅱ）ＣＯＭＰＬＥＸ ＩＮ ＢＲＯＭＡＴＥ－ＰＹＲＵＶＩＣ ＡＣＩＤ ──ＳＵＬＦＵ...

Mechanistic Study of Ruthenium(III) Catalyzed Oxidation of Cyclohexanone by Acidic Bromate

In this work, kinetics and mechanism of Ru(III) catalyzed oxidation of cyclohexanone by acidified solution of potassium bromate has been studied. Present study employ mercuric acetate Hg (OAc)2 as a scavenger for Br¯?ion to prevent parallel oxidation by bromine. The kinetics and mechanism have also been studied in the temperature range of 30°C - 45°C. The reaction exhibits first order kinetics with respect to Ru (III), while zero order kinetics with respect to KBrO3 and HClO4. The influence of Hg(OAc)2 and ionic strength on the rate of reaction was found to be insignificant. Positive effect in the reaction mixture was also observed upon addition of chloride ion;while as the negative effect was revealed with acetic acid. A suitable mechanism in conformity with the kinetic observations has been proposed and the rate law is derived on the basis of obtained data. The various activation parameters such as energy of activation (ΔE*), Arrhenius factor (A), entropy of activation (ΔS*) were calculated from the rate measurements at 30°C, 35°C - 40°C and 45°C.

Health Risk Assessment for Bromate (BrO₃^–) Traces in Ozonated Indian Bottled Water

For this study, bromide and bromate ions in various commercial brands of Indian bottled water samples were estimated using ion chromatography. The measured mean concentration of bromide and bromate ions in water samples was found to be 28.13 μg/L and 11.17 μg/L respectively. The average level of bromate in Indian bottled water was found to be slightly higher (~ 12%) than the acceptable limits (10 μg/L) recommended by USEPA (US Environmental Protection Agency). Though, kinetically, it is predicted that 62.5% (6.25 μg/L) of bromide in bottled water is needed to convert into bromate upon ozonation to exceed the minimum acceptable limits, but the average formation of bromate determined to be only 26.77% of the predicted concentration. Bromate concentration in bottled water showed a strong correlation with bromide suggesting that its formation in water is very much influenced and controlled by bromide content. The objective of the present study was to determine the BrO3–) content of commercially available different brands of bottled drinking water in India and to estimate the health risks to population due to ingestion. Results of estimated excess cancer risk and chemical toxicity risk to Indian population due to ingestion of bottled water were presented and discussed.

X-Ray Crysatllographic and Vibrational Spectroscopic Studies of Thorium Bromate Hydrate

Th(BrO3)3·H2O single crystals were grown from its aqueous solution at room temperature. Single crystal XRD, Raman and FTIR techniques were used to investigate the crystal structure. The crystal structure was solved by Patterson method. The as grown crystals are in monoclinic system with space group P21/c. The unit cell parameters are a = 12.8555(18) ?, b = 7.8970(11) ?, c = 9.0716(10)?, α = 90°, β = 131.568° and γ = 90° and unit cell volume is 689.1(2)?3. Z = 8, R factor is 5.9. The Raman and FTIR studies indicate the lowering of symetry of bromate anion from C3V to C1. Hydrogen bonds with varying strengths are present in the crystal. The centrosymmetric space group P21/c of the crystal is confirmed by the non-coincidence of majority of Raman and IR bands.

Determination and Degradation of Potassium Bromate Content in Dough and Bread Samples Due to the Presence of Metals

Potassium bromate (PB) is used in bread making as an agent of maturation;however, it is classified as a potential carcinogen. In the present study, a rapid, simple, precise and accurate testing method has been developed to determine the level of bromate ions in bread, which is based on a reaction of bromate ions with iodide ions in acidic medium to produce iodine (I2). The absorbance of iodine (I2) was measured at 352 nm, and bromate ions reacted with iodide during the first 3 minutes after initiation of the reaction. The proposed method has been successfully applied to the determination of bromate ions in commercial bread. In this work, we found that bromate ions alone degraded at about 400°C, however, during bread making they degraded at 150°C - 200°C, this mightbe due to the presence of metals [Fe, Mg, Zn, Mn, Cu and Al] in flour which served as catalysts. In this study we found that the use of two grams (2 g) of PB per bag flour (60 kg) was safe.

Ozone and ozone/hydrogen peroxide treatment to remove gemfibrozil and ibuprofen from treated sewage effluent: Factors influencing bromate formation

Reuse of treated sewage effluent is an important option to overcome water scarcity.Conventional wastewater treatment methods are inadequate for the removal of several persistent contaminants such as pharmaceuticals and personal care products(PPCPs).In this study the removal of ibuprofen and gemfibrozil by ozonation and ozone/hydrogen peroxide(O3/H2O2)advanced oxidation process(AOP),as well as the formation of bromate were investigated at different temperatures and pH values.Complete removal of gemfibrozil and a maximum of 80%ibuprofen removal were achieved using ozone dosage of 1.5 mg/L with O3:H2O2 ratio of 1:0.25 in the O3/H2O2 process.The effect of temperature on the removal efficiency of these two compounds was found to be negligible from 25 to 40ᵒC for both processes.pH effect from 6 to 9 was also found to be negligible for gemfibrozil removal,while ibuprofen had relatively lower removal by ozonation at pH 6 compared to higher pH values.Bromate formation was decreased to 0.012 mg/L when the pH was increased to 9.Increasing the temperature to 40ᵒC also resulted in less bromate formation which was the lowest value obtained in this study at 0.0102 mg/L.Addition of H2O2 did not affect the formation of bromate and in some cases it was found to be slightly higher compared with ozonation treatment.

Formation control of bromate and trihalomethanes during ozonation of bromide-containing water with chemical addition: Hydrogen peroxide or ammonia?

To ensure the safety of drinking water,ozone (O3) has been extensively applied in drinking water treatment plants to further remove natural organic matter (NOM).However,the surface water and groundwater near the coastal areas often contain high concentrations of bromide ion (Br-).Considering the risk of bromate (Br O3-) formation in ozonation of the sand-filtered water,the inhibitory efficiencies of hydrogen peroxide (H2O2) and ammonia(NH3) on Br O3-formation during ozonation process were compared.The addition of H2O2effectively inhibited Br O3-formation at an initial Br-concentration amended to 350μg/L.The inhibition efficiencies reached 59.6 and 100%when the mass ratio of H2O2/O3was 0.25and>0.5,respectively.The UV254and total organic carbon (TOC) also decreased after adding H2O2,while the formation potential of trihalomethanes (THMs FP) increased especially in subsequent chlorination process at a low dose of H2O2.To control the formation of both Br O3-and THMs,a relatively large dose of O3and a high ratio of H2O2/O3were generally needed.NH3addition inhibited Br O3-formation when the background ammonia nitrogen(NH3–N) concentration was low.There was no significant correlation between Br O3-inhibition efficiency and NH3dose,and a small amount of NH3–N (0.2 mg/L) could obviously inhibit Br O3-formation.The oxidation of NOM seemed unaffected by NH3addition,and the structure of NOM reflected by synchronous fluorescence (SF) scanning remained almost unchanged before and after adding NH3.Considering the formation of Br O3-and THMs,the optimal dose of NH3was suggested to be 0.5 mg/L.

Bromate formation during oxidation of bromide-containing water by the CuO catalyzed peroxymonosulfate process

Bromate formation has been found in the SO_(4)^(•−)-based oxidation processes,but previous studies primarily focused on the bromate formation in the homogeneous SO_(4)^(•−)-based oxidation processes.The kinetics and mechanisms of bromate formation are poorly understood in the heterogeneous SO_(4)^(•−)-based oxidation processes,although which have been widely studied in the eliminations of micropollutants.In this work,we found that the presence of CuO,a common heterogeneous catalyst of peroxymonosulfate(PMS),appreciably enhanced the bromate formation from the oxidation of bromide by PMS.The conversion ratio of bromide to bromate achieved over 85%within 10 min in this process.CuO was demonstrated to play a multiple role in the bromate formation:(1)catalyzed PMS to generate SO_(4)^(•−),which then oxidizes bromide to bromate;(2)catalyzed the formed free bromine to disproportionate to bromate;(3)catalyzed the formed free bromine to decomposed back into bromide.In the CuO-PMS-Br system,bromate formation increases with increasing CuO dosages,initial CuO and bromide concentrations,but decreases with increasing bicarbonate concentrations.The presence of NOM(natural organic matter)resulted in a lower formed bromate accompanied with organic bromine formation.Notably,CuO catalyzes PMS to transform more than 70%of initial bromide to bromate even after recycled used for six times.The formation of bromate in the PMS catalysis by CuO system was also confirmed in real water.

Inhibition of bromate formation by reduced graphene oxide supported cerium dioxide during ozonation of bromidecontaining water

Ozone(O3)is widely used in drinking water disinfection and wastewater treatment.However,when applied to bromide-containing water,ozone induces the formation of bromate,which is carcinogenic.Our previous study found±at graphene oxide(GO)can enhance the degradation efficiency of micropollutants during ozonation.However,in this study,GO was found to promote bromate formation during ozonation of bromide-containing waters,with bromate yields from the O3/GO process more than twice those obtained using ozone alone.The promoted bromate formation was attributed to increased hydroxyl radical production,as confirmed by the significant reduction(almost 75%)in bromate yield after adding t-butanol(TBA).Cerium oxide(less tfian 5 mg/L)supported on reduced GO(xCeO2/RGO)significantly inhibited bromate formation during ozonation compared with reduced GO alone,and the optimal Ce atomic percentage(x)was determined to be 0.36%,achieving an inhibition rate of approximately 73%.Fourier transform infrared(FT-IR)spectra indicated the transformation of GO into RGO after hydrothermal treatment,and transmission electron microscope(TEM)results showed that CeO2 nanoparticles were well dispersed on the RGO surface.The X-ray photoelectron spectroscopy(XPS)spectra results demonstrated that the Ce^3+/Ce^4+ratio in xCeO2/RGO was almost 3-4 times higher than that in pure CeO2,which might be attributed to the charge transfer effect from GO to CeO2.Furthermore,Ce+on thexCeO2/RGO surface could quench Br-and BrO-to further inhibit bromate formation.Meanwhile,0.36CeO2/RGO could also enhance the degradation efficiency of N,N-diethyl-zn-toluamide(DEET)in synthetic and reclaimed water during ozonation.

Synthesis of α-Bromine-Terminated Polystyrene Macroinitiator and Its Initiation of MMA Polymerization by ATRP

In the present paper the synthesis of block copolymers via the transformation from living anionic polymerization （LAP） to atom transfer radical polymerization （ATRP） was described. α-Bromine-terminated polystyrenes（PStBr） in the LAP step was prepared by using n-BuLi as initiator, tetrahydrofuran （THF） as the activator, α-methylstyrene （α-MeSt） as the capping group and liquid bromine （Br2） as the bromating agent. The effects of reaction conditions such as the amounts of α-MeSt, THF, and Br2 as well as molecular weight of polystyrene on the bromating efficiency （BE） and coupling extent （CE） were examined. The present results show that the yield of PStBr obtained was more than 93. 8% and the coupling reaction was substantially absent. PStBr was further used as the macroinitiator in the polymerization of methyl-methacrylate （MMA） in the presence of copper （I ） halogen and 2, 2’ -bipyridine （bpy） complexes. It was found that the molecular weight of the resulted PSt-b-PMMA increased linearly with the increase of the conversion of MMA and the polydispersity was 1. 2-1.6. The structures of PStBr and P（St-b-MMA） were characterized by 1H NMR spectra.

Catalytic reduction of water pollutants:knowledge gaps,lessons learned,and new opportunities

In this paper,we discuss the previous advances,current challenges,and future opportunities for the research of catalytic reduction of water pollutants.We present five case studies on the development of palladium-based catalysts for nitrate,chlorate,and perchlorate reduction with hydrogen gas under ambient conditions.We emphasize the realization of new functionalities through the screening and design of catalytic metal sites,including(i)platinum group metal(PGM)nanoparticles,(ii)the secondary metals for improving the reaction rate and product selectivity of nitrate reduction,(iii)oxygen-atom-transfer metal oxides for chlorate and perchlorate reduction,and(iv)ligand-enhanced coordination complexes for substantial activity enhancement.We also highlight the facile catalyst preparation approach that brought significant convenience to catalyst optimization.Based on our own studies,we then discuss directions of the catalyst research effort that are not immediately necessary or desirable,including(1)systematic study on the downstream aspects of under-developed catalysts,(2)random integration with hot concepts without a clear rationale,and(3)excessive and decorative experiments.We further address some general concerns regarding using H2 and PGMs in the catalytic system.Finally,we recommend future catalyst development in both“fundamental”and“applied”aspects.The purpose of this perspective is to remove major misconceptions about reductive catalysis research and bring back significant innovations for both scientific advancements and engineering applications to benefit environmental protection.

Catalytic kinetic spectrophotometric determination of cerium

A new procedure for the determination of cerium was established using the catalytic effect of Ce(IV) on the oxidation of tribromoarsenazo(TB-ASA) by potassium bromate.In 0.080 mol/L sulfuric acid medium,the maximum absorption peak of Ce(IV)-(TB-ASA)-KBrO3 system is at 510 nm.The amount of Ce(IV) and the difference of absorbance(△A) showed a good linear relationship over the range of 5.7×10-8-5.1×10-7 mol/L.The regression equation is △A=2.3×10-11 C(C:mol/L)+0.0196,with a regression coefficient of 0.9914 at the wavelength.The detection limit of the method was 5.1×10-8 mol/L ng/mL.This method was used in the determination of cerium in human blood and chicken liver samples.For the eleventh replicate determinations,its relative standard deviation was 3.04%-3.28%.The recovery of standard addition of the method was 100.7%-104.2 %.

The role of metal oxides on oxidant decay and disinfection byproduct formation in drinking waters: Relevance to distribution systems

Maintaining a residual disinfectant/oxidant(e.g., chlorine and chlorine dioxide), is a generally used strategy to control microbial contaminants and bacterial regrowth in distribution systems. Secondarily oxidant, such as hypobromous acid(HOBr), can be formed during chlorination of bromide-containing waters. The decay of oxidants and formation of disinfection byproducts(DBPs) due to the interaction between oxidants and selected metal oxides were studied. Selected metal oxides generally enhanced the decay of these halogencontaining oxidants via three pathways:(1) catalytic disproportionation to yield an oxidized form of halogen(i.e., halate) and reduced form(halide for chlorine and bromine or chlorite for chlorine dioxide),(2) oxygen formation, and(3) oxidation of a metal in a reduced form(e.g., cuprous oxide) to a higher oxidation state. Cupric oxide(Cu O) and nickel oxide(Ni O)showed significantly strong abilities for the first pathway, and oxygen formation was a side reaction. Cuprous oxide can react with oxidants via the third pathway, while goethite was not involved in these reactions. The ability of Cu O on catalytic disproportionation of HOBr remained stable up to four cycles. In chlorination process, bromate formation tends to be important(exceeding 10 μg/L) when initial bromide concentration is above 400 μg/L in the presence of dissolved organic matter. Increasing initial bromide concentrations increased the formation of DBPs and calculated cytotoxicity, and the maximum was observed at p H8.6 during chlorination process. Therefore, the possible disinfectant loss and DBP formation should be carefully considered in drinking water distribution systems.

4-Benzamido-TEMPO Catalyzed Oxidation of a Broad Range of Alcohols to the Carbonyl Compounds with NaBrO_(3) under Mild Conditions

4-Benzamido-TEMPO catalyzed oxidation system for conversion of a wide range of alcohols to the aldehydes or ketones with NaBrO_(3) under room temperature conditions has been developed.The credible,operationally con-venient and economical,and condition mild oxidation protocol is particularly of interest in laboratory and in fine chemicals manufacture.