The Effect of Bromide ion in Water Treatment. II. A Literature Review of Ozone and Bromide ion Interactions and the Formation of Organic Bromine Compounds

Where bromide ion is found in water used as a source of drinking water, and chlorination is used for disinfection, bromide ion is oxidized to bromine and can result in the formation of organic bromine compounds. There are presently no treatment techniques available for economic removal of bromide ion. A potential treatment strategy is to use an alternative oxidant; ozone is one such alternative. This review presents the reactions of ozone and bromide ion. Understanding of these reactions leads to possible treatment strategies when ozone is used, in the presence of bromide ion, to minimize the formation of trihalomethanes.     

The Reaction of Ozone with Bisulfide (HS−) in Aqueous Solution – Mechanistic Aspects

The ozone demand to oxidize HS^?/H₂S [pK_a(H₂S) = 6.9, k(HS^? + O₃) = 3 × 10⁹ M^?1 s^?1, k(H₂S + O₃) = 3 × 10⁴ M^?1 s^?1] to SO₄ ^2? is only 2.4 mol ozone per mol SO₄ ^2? formed, much lower than stoichiometric 4.0 mol/mol if a series of O-transfer reactions would occur. As primary step, the formation of an ozone adduct to HS^?, HSOOO^–, is suggested that decomposes into HSO^– and singlet oxygen (16%) or rearranges into peroxysulfinate ion, HS(O)OO^– (84%). Potential reactions of the above intermediates are discussed. Some of these can account for the low ozone demand.     

Practical Studies of the Electrolysis and Volatilization of the Bromide from Drinking Water to Minimize Bromate Production by Ozonation

In four recently published articles, a process for the oxidation of bromide to bromine and the volatilization of bromine from drinking water sources was presented. This process was shown to be able to remove up to 35% percent of the bromide found naturally in the California State Water Project. Although bromide itself is quite harmless, it has been shown to react with commonly used disinfectants to produce compounds or disinfection by-products (DBPs) of suspected carcinogens. Bromide reacts with ozone to form bromate. This article presents two studies of pilot scale, flow-through electrolytic reactors that oxidize bromide to bromine and volatilize bromine at <pH 3.5, which occurs at the anode as a result of the oxidation of water. One reactor had 14 anodes that were 91 cm deep and the other had 13 anodes 1.2 cm deep. The bromide removal rates were studied at several different water flows and power settings for different bromide concentrations for both reactors. The results show removal of bromide is impacted by water flows and power settings for different bromide concentrations. Effluent from the deep reactor did show some reduction in bromate concentration as compared to control samples but the results were inconsistent. This appeared to be caused by significant differences in the ozone demand produced by different experimental conditions, difficulty determining the concentration of chlorine, and the use of hydrogen peroxide as a dechlorinating agent. Using the shallow reactor, these difficulties were overcome by developing a more consistent determining chlorine concentration, using much larger ozone doses to overwhelm the ozone demand, and by using ascorbic acid instead of hydrogen peroxide. With these changes, it could be shown that the electrolytic reactor not only lowered the concentration of bromide in the water but when ozonated, the amount of bromate formed was reduced in direct proportion to the amount of bromide removed for an equal dose of ozone.     

A Theoretical Study on the Mechanism and Kinetic of the Reaction between Ozone and Benzene

Ozone has been widely used to degrade volatile organic compounds (VOCs) in combination with other methods such as ultraviolet light, adsorption, thermal and catalytic incineration. Despite its fundamental importance, the mechanism and kinetics of the reaction between ozone and VOCs are still lacking of detailed investigation. It is well known that quantum chemical calculation is a well-established method for investigating the chemical reactions. In this paper, quantum chemical calculation is employed to investigate the mechanism and kinetics of the reaction between ozone and VOCs exemplified by benzene. The microcosmic reaction process was depicted and discussed in detail based on geometry optimizations made using the UB3LYP/6-31G (d) method. According to the mechanism study, the kinetic parameters were also calculated by the classical transition state theory (TST). The calculated activation energy is 14.90 kcal/mol at the QCISD(t)/6-311g(d,p)//UB3LYP/6-31G(d) level of theory, while the obtained Arrhenius expression is that, k=1.05×10¹¹ exp(-61527/RT) (cm³·mole^?1·s^?1). Both the activation energy and the Arrhenius expression are in good agreement with the experimental results, which indicated that the mechanism and kinetic study of the reaction between benzene with ozone by employing quantum chemical calculation was reasonable and reliable.     

靛族染料化合物结构与性能的密度泛函理论研究

在密度泛函理论(DFT)的B3LYP／6-31G^*水平上对一系列靛族染料化合物的几何构型进行优化计算：在获得基态稳定结构的基础上，应用含时密度泛函理论(TD-DFT)在相同水平下计算其电子吸收光谱，探讨了不同给电子基团和发色体系的延伸对电子吸收光谱的影响，得到了与实验基本一致的变化规律。结果表明，给电子能力的增强和发色体系的纵向延伸均使光谱产生一定红移，通过对前线轨道组成进行自然布居分析，揭示了靛族染料的发光均源自分子中HOMO-LUMO(П→П^*)电子跃迁。     

Periodic Density Functional Theory Investigation of the Uranyl Ion Sorption on Three Mineral Surfaces: A Comparative Study

Canister integrity and radionuclides retention is of prime importance for assessing the long term safety of nuclear waste stored in engineered geologic depositories. A comparative investigation of the interaction of uranyl ion with three different mineral surfaces has thus been undertaken in order to point out the influence of surface composition on the adsorption mechanism(s). Periodic DFT calculations using plane waves basis sets with the GGA formalism were performed on the TiO₂(110), Al(OH)₃(001) and Ni(111) surfaces. This study has clearly shown that three parameters play an important role in the uranyl adsorption mechanism: the solvent (H₂O) distribution at the interface, the nature of the adsorption site and finally, the surface atoms’ protonation state.     

取代乙烷交叉式与重叠式稳定性的密度泛函理论研究

在密度泛函DFT/B3LYP理论水平优化结构,结合Aug-CC-pVDZ基组计算了17种取代乙烷交叉式与重叠式的电子能量。结果发现,相关能差值(ΔEc)与总能量差值(ΔE)的相关回归系数最高(R~2=0.95),交换能差值(ΔEx)与ΔE相关回归系数次之(R~2=0.93)。选择ΔEc与ΔEx对ΔE进行多元线性拟合,得到其相关回归系数(R~2=0.95),再用拟合公式计算ΔE(实际),并与计算得到的ΔE(理论)进行线性拟合,得到其相关回归系数R~2=0.95。我们认为,交叉式取代乙烷的构象稳定性主要起源于其分子内的相关能(Ec)和交换能(Ex)作用。     

Study on By-Products of Ozonation during Ammonia Removal under the Existence of Bromide: Factors Affecting Formation and Removal of the By-Products

Factors affecting the formation of by-products of ozonation during ammonia removal under the existence of bromide were investigated. The presence of reducible N compounds could significantly reduce the formation of bromate and brominated organics; however, it was difficult to completely prevent formation of the by-products. It was therefore concluded that while the method used in this study was an effective process to decompose ammonia, it should be applied to the treatment of wastewaters containing low concentration of TOC. For power plant condensate demineralization wastewater containing TOC of 3 to 4mg/L, TOX formed during ammonia removal ranged from 0.20 to 0.30 mgBr L^?1. The only halogenated organic substance of the power plant wastewater detected on GC spectrum was bromoform, whose concentration varied from 0.11 to 0.14 mg L^?1. Column test results indicated that bromate could almost completely be decomposed to bromide by activated carbon under proper space velocity and pH. Activated carbon was also very effective in adsorption of CHBr₃: 1 g activated carbon adsorbed ca. 20.3 mg of CHBr₃.