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The efficiency of elimination of organic UV filters by ozonation and UV 254nm /H 2 O 2 processes was assessed and predicted in simulated treatments of sewage-impaired drinking water and wastewater effluent in bench-scale experiments. Second-order rate constants (k) for the reactions of the eight UV filters with ozone and OH were determined by quantum chemical calculations and competition kinetics methods, respectively. The UV filters containing phenolic (ethylhexyl-salicylate, homosalate, and benzophenone-3) and olefinic moieties (4-methylbenzylidene-camphor, benzyl-cinnamate, and 2-ethylhexyl-4-methoxycinnamate) showed high ozone reactivity (k ≥ 8 × 10 4  M -1 s -1  at pH 7), while those without such electron-rich moieties (isoamyl-benzoate and benzophenone) were ozone-refractory. All the UV filters showed high OH reactivity (k ≥ 6.2 × 10 9  M -1 s -1 ). In concordance with the rate constant information, the phenolic and olefinic UV filters were efficiently eliminated by ozone treatment, requiring specific ozone doses of <0.5 mgO 3 /mgDOC for ∼100% elimination. The UV filters were eliminated by ≤ 38% at a UV fluence of 1500 mJ/cm 2 in the UV 254nm -only treatment. Rapid photoisomerisation between the E and Z geometric isomers was observed for the olefinic UV filter, benzyl-cinnamate. The addition of H 2 O 2 (10 mg/L) greatly enhanced the elimination of all UV filters, indicating that OH was the main contributor to their elimination in the UV 254nm /H 2 O 2 treatment. A chemical kinetics approach developed previously for ozonation and UV/H 2 O 2 processes was shown to predict the elimination of the UV filters in the tested water matrices reasonably well, demonstrating that the chemical kinetics method can be used for a priori prediction of micropollutant elimination in oxidative treatment processes for potable reuse of municipal wastewater effluents., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Compounds with N,N-dimethylhydrazine moieties ((CH 3 ) 2 N-N-) form N-nitrosodimethylamine (NDMA) during ozonation, but the relevant reaction chemistry is hitherto poorly understood. This study investigated the reaction kinetics and mechanisms of NDMA formation during ozonation of unsymmetrical dimethylhydrazine (UDMH) and daminozide (DMZ) as structural model N,N-dimethylhydrazine compounds. The reaction of ozone with these NDMA precursor compounds was fast, and k O3 at pH 7 was 2 × 10 6  M -1  s -1 for UDMH and 5 × 10 5  M -1  s -1 for DMZ. Molar NDMA yields (i.e., Δ[NDMA]/Δ[precursor] × 100) were 84% and 100% for UDMH and DMZ, respectively, determined at molar ozone dose ratio ([O 3 ] 0 /[precursor] 0 ) of ≥4 in the presence of tert-butanol as hydroxyl radical (OH) scavenger. The molar NDMA yields decreased significantly in the absence of tert-butanol, indicating OH formation and its subsequent reaction with the parent precursors forming negligible NDMA. The k OH at pH 7 was 4.9 × 10 9  M -1  s -1 and 3.4 × 10 9  M -1  s -1 for UDMH and DMZ, respectively. Reaction mechanisms are proposed in which an ozone adduct is formed at the nitrogen next to N,N-dimethylamine which decomposes via homolytic and heterolytic cleavages of the -N + -O-O-O - bond, forming NDMA as a final product. The heterolytic cleavage pathway explains the significant OH formation via radical intermediates. Overall, significant NDMA formation was found to be unavoidable during ozonation or even O 3 /H 2 O 2 treatment of waters containing N,N-dimethylhydrazine compounds due to their rapid reaction with ozone forming NDMA with high yield. Thus, source control or pre-treatment of N,N-dimethylhydrazine precursors and post-treatment of NDMA are proposed as the mitigation options., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

To model thioether-copper coordination chemistry including oxidative reactivity, such as occurs in the copper monooxygenases peptidylglycine -hydroxylating monooxygenase (PHM) and dopamine beta-hydroxylase (DbetaH), we have synthesized new tridentate N2S ligands LSEP and LSBz [LSEP = methyl(2-phenethylsulfanylpropyl)(2-pyridin-2-ylethyl)amine; LSBz = (2-benzylsulfanylpropyl)methyl(2-pyridin-2-ylethyl)amine)]. Both copper(I) and copper(II) complexes have been prepared, and their respective O2 and H2O2 chemistry has been studied. Under mild conditions, oxygenation of [(LSEP)CuI]+ (1a) and [(LSBz)CuI]+ (2a) leads to ligand sulfoxidation, thus exhibiting copper monooxygenase activity. A copper(II) complex of this sulfoxide ligand product, [(LSOEP)CuII(CH3OH)(OClO3)2], has been structurally characterized, demonstrating Cu-Osulfoxide ligation. The X-ray structure of [(LSEP)CuII(H2O)(OClO3)]+ (1b) and its solution UV-visible spectral properties [S-CuII LMCT band at 365 nm (MeCN solvent); epsilon = 4285 M-1 cm-1] indicate the thioether sulfur atom is bound to the cupric ion in both the solid (CuII-S distance: 2.31 A) and solution states. Reaction of 1b with H2O2 leads to sulfonation via the sulfoxide; excess hydrogen peroxide gives mostly sulfone product. These results may provide some insight into recent reports concerning protein methionine oxidation, showing the potential importance of copper-mediated oxidation processes in certain biological settings.

The objective of this study was to elucidate the degradation pathways of dimethylsulfoxide (DMSO) during its mineralization caused by UV/H(2)O(2) treatment. In order to accomplish this, we measured the concentration time-profiles of DMSO and its degradation intermediates during the UV/H(2)O(2) treatment. In addition, we proposed a kinetic model that could account for the degradation pathways of DMSO during its UV/H(2)O(2) treatment. The results show that the degradation of DMSO by the UV/H(2)O(2) treatment can be classified into two major pathways, and this is supported by both the analysis of the intermediates and total organic carbon (TOC) measurements. Firstly, DMSO was degraded into sulfate (SO(4)(2-)) through the formation of methansulfinate (CH(3)SO(2)(-)) and methansulfonate (CH(3)SO(3)(-)) as sulfur-containing intermediates. One of the two carbon constituents of DMSO was highly resistant to mineralization, due to the formation of methansulfonate, which reacted very slowly with (.-)OH k = 0.8 x 10(7) M(-1)s(-1)). Secondly, the other carbon constituent of DMSO was relatively easily mineralized through the formation of formaldehyde (HCHO) and formate (HCO(2)(-)) as non-sulfur-containing intermediates. The kinetic model proposed in this study for the degradation of DMSO by (.-)OH in the UV/H(2)O(2) process was able to successfully predict the patterns of concentration time-profiles of all components during the UV/H(2)O(2) treatment of DMSO.

The influence of various reaction parameters on herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) removal were examined in the photo/ferrioxalate/H(2)O(2) system, with regard to: (1) sulfate, phosphate, and z.rad;OH scavenger, as solution constituent; and (2) light intensity, ferrioxalate, H(2)O(2), and oxalate concentration, as operating parameter. In terms of 2,4-D removal, the photo/ferrioxalate/H(2)O(2) system has always been superior to the photo/Ferric ion/H(2)O(2) system, despite the high presence of anions (sulfate 100 mM, phosphate 1 mM) or z.rad;OH scavenger. Not only the rate of 2,4-D removal, but also the decomposition rate of H(2)O(2) and oxalate proportionally increase with light intensity. The ferrioxalate concentration determines the light absorption fraction, and thus, controls the rates of 2,4-D removal, and the decomposition of H(2)O(2) and oxalate, are predicted from kinetic formulations. The optimal concentration of H(2)O(2) and oxalate, according to the extent of the z.rad;OH scavenging reaction with these reagents, has been demonstrated for 2,4-D removal. It was found that an increasing oxalate concentration, which bears the burden of increased dissolved organic carbon (DOC), does not occur. This is because its decomposition, as a result of the photochemical reduction of the ferric oxalate complex, results in a decrease of the equivalent DOC. The importance of the key reaction factors to be considered, when applying this system to real wastewater treatment, is also discussed.

This study demonstrates the importance of reaction temperature on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). In addition, we provide a mechanistic explanation for the temperature dependence of 2,4-D degradation. Thermal enhancement of 2,4-D degradation and H(2)O(2) decomposition was measured in the absence and in the presence of the z.rad;OH scavenger (t-butanol). The half-life for 2,4-D degradation was reduced by more than 70-fold in the absence of t-butanol, and by more than 700-fold, in the presence of t-butanol, when the reaction temperature was increased from 10 to 50 degrees C. In addition, similar temperature relationships were found for H(2)O(2) decomposition. The major reason for the high temperature dependence of the Fe(3+)/H(2)O(2) system in the case of 2,4-D degradation is due to the dependence of the initiation reaction of the Fe(3+)/H(2)O(2) system (i.e., Fe(3+)+H(2)O(2)-->Fe(2+)+HO(2)(z.rad;)+H(+) upon temperature), which is entirely consistent with the kinetics of the activation energy. In the presence of a z.rad;OH scavenger, the initiation reaction of the Fe(3+)/H(2)O(2) system became a determining factor of this temperature dependence, whereas in the absence of z.rad;OH scavenger, several other radical reactions played a role and this result in an apparent decrease in the activation energy for 2,4-D degradation. Moreover, the enhanced 2,4-D removal at higher temperatures did not alter H(2)O(2) utilization. The practical implications of the thermal enhancement of the Fe(3+)/H(2)O(2) system are discussed.

Bacterial plant pathogens often encounter reactive oxygen species (ROS) during host invasion. In foliar bacterial pathogens, multiple regulatory proteins are involved in the sensing of oxidative stress and the activation of the expression of antioxidant genes. However, it is unclear whether xylem-limited bacteria, such as Xylella fastidiosa, experience oxidative stress during the colonization of plants. Examination of the X. fastidiosa genome uncovered only one homologue of oxidative stress regulatory proteins, OxyR. Here, a knockout mutation in the X. fastidiosa oxyR gene was constructed; the resulting strain was significantly more sensitive to hydrogen peroxide (H2 O2 ) relative to the wild-type. In addition, during early stages of grapevine infection, the survival rate was 1000-fold lower for the oxyR mutant than for the wild-type. This supports the hypothesis that grapevine xylem represents an oxidative environment and that X. fastidiosa must overcome this challenge to achieve maximal xylem colonization. Finally, the oxyR mutant exhibited reduced surface attachment and cell-cell aggregation and was defective in biofilm maturation, suggesting that ROS could be a potential environmental cue stimulating biofilm development during the early stages of host colonization.

The potential of horseradish peroxidase combined with hydrogen peroxidase (HRP/H 2 O 2 ) catalytic process was assessed as an enhanced wastewater treatment technology to eliminate trace organic contaminants (micropollutants). Kinetic experiments with 17α-ethinylestradiol (EE2) as a phenolic micropollutant in synthetic buffered solutions showed that the apparent first-order rate constant of EE2 transformation ( k EE2 ) increased linearly with increasing HRP concentration but was independent of the concentrations of H 2 O 2 and EE2. The observed kinetic behaviors of EE2 could be well explained by the known chemistry of the HRP/H 2 O 2 system considering the reaction of Compound II with EE2 as the rate-limiting step in the catalytic cycle of HRP under the condition of excess H 2 O 2 over HRP. Using this HRP/H 2 O 2 kinetic model, the second-order rate constants of the reaction of Compound II (k 3 ) with a few selected phenolic micropollutants including EE2 and phenol and aniline could be determined and compared with those from the literature. Good correlations were found between the k 3 of various phenolic or anilinic compounds (from this study and the literature) versus Hammett sigma constants, which can be used for predicting the elimination efficiency of phenolic or anilinic micropollutants. Experiments conducted using lake water and wastewater effluent matrices showed that significant elimination of phenolic micropollutants (i.e., % elimination levels of 20%–100%) could be achieved under the following treatment condition: 1.4–5.6 nM (12–48 U/L) of HRP, 20 μM of H 2 O 2 , and 1 h of reaction time. Elimination of the other tested micropollutants without phenolic moieties was less than 5%. The elimination levels of phenolic micropollutants (e.g., EE2) in real water matrices spiked at 2 μM could be well predicted by the HRP/H 2 O 2 kinetic model with the corresponding k 3 value. However, relatively lower elimination levels were observed when the phenolic micropollutants were spiked at 1 μg/L, indicating some reduction in the performance of the HRP/H 2 O 2 process for eliminating phenolic micropollutants present at environmentally relevant concentrations (e.g., sub μg/L). [ABSTRACT FROM AUTHOR]

The influence of various reaction parameters on herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) removal were examined in the photo/ferrioxalate/H2O2 system, with regard to: (1) sulfate, phosphate, and ⋅OH scavenger, as solution constituent; and (2) light intensity, ferrioxalate, H2O2, and oxalate concentration, as operating parameter. In terms of 2,4-D removal, the photo/ferrioxalate/H2O2 system has always been superior to the photo/Ferric ion/H2O2 system, despite the high presence of anions (sulfate 100 mM, phosphate 1 mM) or ⋅OH scavenger. Not only the rate of 2,4-D removal, but also the decomposition rate of H2O2 and oxalate proportionally increase with light intensity. The ferrioxalate concentration determines the light absorption fraction, and thus, controls the rates of 2,4-D removal, and the decomposition of H2O2 and oxalate, are predicted from kinetic formulations. The optimal concentration of H2O2 and oxalate, according to the extent of the ⋅OH scavenging reaction with these reagents, has been demonstrated for 2,4-D removal. It was found that an increasing oxalate concentration, which bears the burden of increased dissolved organic carbon (DOC), does not occur. This is because its decomposition, as a result of the photochemical reduction of the ferric oxalate complex, results in a decrease of the equivalent DOC. The importance of the key reaction factors to be considered, when applying this system to real wastewater treatment, is also discussed. [Copyright &y& Elsevier]

Oxidative treatment of iodide-containing waters can lead to a formation of potentially toxic iodinated disinfection byproducts (I-DBPs). Iodide (I−) is easily oxidized to HOI by various oxidation processes and its reaction with dissolved organic matter (DOM) can produce I-DBPs. Hydrogen peroxide (H 2 O 2) plays a key role in minimizing the formation of I-DBPs by reduction of HOI during H 2 O 2 -based advanced oxidation processes or water treatment based on peracetic acid or ferrate(VI). To assess the importance of these reactions, second order rate constants for the reaction of HOI with H 2 O 2 were determined in the pH range of 4.0–12.0. H 2 O 2 showed considerable reactivity with HOI near neutral pH (k app = 9.8 × 103 and 6.3 × 104 M−1s−1 at pH 7.1 and 8.0, respectively). The species-specific second order rate constants for the reactions of H 2 O 2 with HOI, HO 2 − with HOI, and HO 2 − with OI− were determined as k H2O2+HOI = 29 ± 5.2 M−1s−1, k HO2 - +HOI = (3.1 ± 0.3) × 108 M−1s−1, and k HO2 - +OI − = (6.4 ± 1.4) × 107 M−1s−1, respectively. The activation energy for the reaction between HOI and H 2 O 2 was determined to be E a = 34 kJ mol−1. The effect of buffer types (phosphate, acetate, and borate) and their concentrations was also investigated. Phosphate and acetate buffers significantly increased the rate of the H 2 O 2 –HOI reaction at pH 7.3 and 4.7, respectively, whereas the effect of borate was moderate. It could be demonstrated, that the formation of iodophenols from phenol as a model for I-DBPs formation was significantly reduced by the addition of H 2 O 2 to HOI- and phenol-containing solutions. During water treatment with the O 3 /H 2 O 2 process or peracetic acid in the presence of I−, O 3 and peracetic acid will be consumed by a catalytic oxidation of I− due to the fast reduction of HOI by H 2 O 2. The O 3 deposition on the ocean surface may also be influenced by the presence of H 2 O 2 , which leads to a catalytic consumption of O 3 by I−. Image 1 • The reactivity between HOI and H 2 O 2 was assessed in the pH range of 4–12. • Oxidation of I−-and H 2 O 2 -containing water leads to limited I-DBPs formation. • The reactivity of HO 2 − with HOX increases in the order of HOCl < HOI < HOBr. • I−-controlled O 3 deposition on seawater surface can be enhanced in presence of H 2 O 2. [ABSTRACT FROM AUTHOR]

• Strong sunlight irradiation increased H 2 O 2 production in freshwater. • The type II prx and gshB genes were highly up-regulated in PCC7806 cells exposed to H 2 O 2. • High-catalase-bacterial communities protected M. aeruginosa cells from H 2 O 2 toxicity. • ROS-mediated M. aeruginosa death could be alleviated by the class Alphaproteobacteria. Microcystis aeruginosa , an important cyanobloom-forming cyanobacterium, is sensitive to the high light intensity and consequent oxidative stress. Based on our genomic and transcriptomic analyses of H 2 O 2 -treated cells, many genes involved in photosynthesis, Calvin cycle, and microcystin synthesis were downregulated, whereas several toxin-antitoxin genes, DNA repair genes, and H 2 O 2 -defense systems such as peroxiredoxins and glutathione synthesis were upregulated. Axenic M. aeruginosa was then co-cultured with synthetic bacterial communities collected from 15 different freshwater samples with exhibiting different degrees of H 2 O 2 -production and catalase activities. Our analyses indicated that H 2 O 2 -resistant bacterial communities favored the growth and photosynthetic activity of M. aeruginosa cells under either H 2 O 2 treatment or high light conditions. Nanopore-based bacterial community analyses indicated that these growth-promoting effects were likely attributable to a high proportion of Alphaproteobacteria (e.g., Brevundimonas and Ochrobactrum species), which protected M. aeruginosa cells from H 2 O 2 toxicity. Further, these bacterial communities exhibited higher catalase activity levels and faster O 2 production rates upon H 2 O 2 detoxification. Taken together, our findings newly suggest that the occurrence of catalase-less M. aeruginosa blooms is largely influenced by the surrounding microbiota during high light and organic-rich conditions. [Display omitted] [ABSTRACT FROM AUTHOR]

The exploration of environmentally friendly hypergolic combinations of ionic liquid fuels and hydrogen peroxide as an oxidizer offers opportunities to replace commonly used conventional toxic, corrosive and carcinogenic hydrazine-based liquid hypergolic combinations. Various research opportunities await regarding the detailed investigations of green hypergolic ionic liquids (HILs) with rocket grade hydrogen peroxide (RGHP, >85% H 2 O 2). In this work, the combustion of HILs 1-ethyl-3-methyl imidazolium cyanoborohydride ([EMIM][BH 3 CN]) and 1-allyl-3-ethyl imidazolium cyanoborohydride ([AEIM][BH 3 CN]), and HIL-additive mixtures with 95% H 2 O 2 has been investigated. A new additive, 1,3-dimethyl imidazolium copper iodide ([diMIM] n [Cu 2 I 3 ] n) was synthesized successfully; a structural investigation was performed through the use of single-crystal x-ray diffraction analysis through which a crystal density of 3.22 g/cm3 was revealed. The physicochemical properties (density, viscosity, and decomposition temperature) as well as performance parameters (ignition delay and specific impulse) of 2 to 15 wt% of [diMIM] n [Cu 2 I 3 ] n in [EMIM][BH 3 CN] were determined. A 15 wt% of [diMIM] n [Cu 2 I 3 ] n exhibited ignition delay time (IDT) values of 13 and 29 ms under fuel-rich and oxidizer-rich conditions, respectively; these IDT values are 100 times lower than those for [EMIM][BH 3 CN]. Interestingly, [diMIM] n [Cu 2 I 3 ] n -[EMIM][BH 3 CN] combinations revealed high density (>0.98 g/cm3), good thermal (>200 °C) and chemical stability, and 5.6–6.0% higher density specific impulse than those found for unsymmetrical dimethyl hydrazine. The additive-promoted hypergolic combustion of HIL with RGHP opens a new avenue to the replacement of conventional toxic hypergolic combinations. [ABSTRACT FROM AUTHOR]

Ozonation, a viable option for improving wastewater effluent quality, requires process optimization to ensure the organic micropollutants (OMPs) elimination and disinfection under minimized byproduct formation. This study assessed and compared the efficiencies of ozonation (O 3) and ozone with hydrogen peroxide (O 3 /H 2 O 2) for 70 OMPs elimination, inactivation of three bacteria and three viruses, and formation of bromate and biodegradable organics during the bench-scale O 3 and O 3 /H 2 O 2 treatment of municipal wastewater effluent. 39 OMPs were fully eliminated, and 22 OMPs were considerably eliminated (54 ± 14%) at an ozone dosage of 0.5 gO 3 /gDOC for their high reactivity to ozone or •OH. The chemical kinetics approach accurately predicted the OMP elimination levels based on the rate constants and exposures of ozone and •OH, where the quantum chemical calculation and group contribution method successfully predicted the ozone and •OH rate constants, respectively. Microbial inactivation levels increased with increasing ozone dosage up to ∼3.1 (bacteria) and ∼2.6 (virus) log 10 reductions at 0.7 gO 3 /gDOC. O 3 /H 2 O 2 minimized bromate formation but significantly decreased bacteria/virus inactivation, whereas its impact on OMP elimination was insignificant. Ozonation produced biodegradable organics that were removed by a post-biodegradation treatment, achieving up to 24% DOM mineralization. These results can be useful for optimizing O 3 and O 3 /H 2 O 2 processes for enhanced wastewater treatment. [Display omitted] • 70 OMPs and 6 bacteria/viruses in sewage effluent were treated by O 3 and O 3 /H 2 O 2. • 33 k O3 and 23 k •OH were newly reported, calculated from QSAR and GCM. • Good prediction of OMP removals using O 3 /•OH reactivity and exposure. • The microbial inactivation was lower than the linear kinetic model prediction. • O 3 /H 2 O 2 minimized bromate formation but decreased microbial inactivation than O 3. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hypergolic energetic copper complexes are investigated as new promoters. • Low ignition delay of "green" fuels with 70% and 95% hydrogen peroxide. • Promoter lowers the ignition delay of ionic liquids by 1000 times. • Non-hypergolic to hypergolic fuels by using promoter. Ionic liquid-with-promoter fuels and H 2 O 2 oxidizer require optimization and further exploration of inexpensive initiators that can be understood at the molecular level; it is advantageous when exacting structural characterization comparisons can also be made. For the first time, hypergolic energetic copper(II) complexes viz. [CuII(1-H-imidazole) 4 (BH 3 CN)][BH 3 CN] (Cu-P1) and [CuII(1-methyl imidazole) 4 (BH 3 CN) 2 (Cu-P2) were developed as new 'promoters' for "green" space vehicle propulsion. Cu-P1 and Cu-P2 exhibited ignition delay times (IDTs) of 3.75 and 8.5 ms, respectively, with 95% H 2 O 2. The superior solubility of Cu-P1 in ionic and non-ionic fuels helped to promote the hypergolic ignition of green liquid fuels. The ionic liquid, 1-ethyl-3-methyl imidazolium cyanoborohydride ([EMIM][BH 3 CN]), non-ionic tetraglyme, and mixtures thereof (1:1, wt/wt%) were employed. A 13 wt% of Cu-P1 in [EMIM][BH 3 CN] improved the IDT from >1000 ms to 9.50 ms with 95% H 2 O 2 and from >5000 ms to 21.25 ms with 70% H 2 O 2. Hence, the development of a suitable energetic promoter, soluble in ionic liquid, gained significant attention for "green" bipropellant development. Interestingly, tetraglyme is non-hypergolic with H 2 O 2 ; a 13 wt% Cu-P1 induced the hypergolic ignition with an IDT of 9.0 ms (95% H 2 O 2). Moreover, the fuel mixture of [EMIM][BH 3 CN] and tetraglyme (1:1, wt/wt%) with 13 wt% Cu-P1 also revealed the shortest IDT of 7.75 ms (95% H 2 O 2) and 16.5 ms (70% H 2 O 2). The superior ignition performance, reasonable viscosity and density, long-term stability of promoter in the fuel, and comparable theoretical performance of hypergolic propellants are advantages of our approach. [ABSTRACT FROM AUTHOR]