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Recently, the activation of chlorine dioxide (ClO2) by metal(oxide) for soil remediation has gained notable attention. However, the related activation mechanisms are still not clear. Herein, the variation of iron species and ClO2, the generated reactive oxygen species, and the toxicity of the degradation intermediates were explored and evaluated with nanoscale zero-valent iron (nFe0) being employed to activate ClO2 for soil polycyclic aromatic hydrocarbon (PAH) removal. With an optimized ClO2/nFe0 molar ratio of 15:1 and a soil/water ratio of 3:1, the degradation efficiency of phenanthrene improved 12% in comparison with that of a ClO2-alone system. The presence of nFe0 significantly promoted ClO2 consumption (improved 85.4%) but restrained ClO2− generation (reduced 22.5%). The surface Fe(II) and soluble Fe(II) in the ClO2/nFe0 system was 2.0-fold and 2.8-fold that in the nFe0 system after 2 min. Electron paramagnetic resonance analysis, along with quenching experiments, revealed that Fe(IV), HOCl, and •OH dominated phenanthrene degradation in a ClO2/nFe0 system, with oxidation contributions, respectively, of 34.3%, 52.8% and 12.9%. The degradation intermediates of PAHs in the ClO2/nFe0 system had lower estimated toxicity than those of the ClO2 system. The lettuces grown in ClO2/nFe0-treated soil displayed better results in bioassay indexes than those grown in ClO2-treated soil. This study offers new perspectives for the remediation of organic-pollutant-contaminated soil by using metal-activated ClO2 technology. [ABSTRACT FROM AUTHOR]

Hydroxyl radicals (•OH), the most potent oxidants among reactive oxygen species (ROS), are a major contributor to oxidative damage of biomacromolecules, including DNA, lipids, and proteins. The overproduction of •OH is implicated in the pathogenesis of numerous diseases such as cancer, neurodegenerative disorders, and some cardiovascular pathologies. Given the localized nature of •OH-induced damage, detecting •OH, specifically near DNA and within organelles, is crucial for understanding their pathological roles. The major challenge of •OH detection results from their short half-life, high reactivity, and low concentrations within biological systems. As a result, there is a growing need for the development of highly sensitive and selective probes that can detect •OH in specific cellular regions. This review focuses on the advances in fluorescence probes designed to detect •OH near DNA and within cellular organelles and membranes. The key designs of the probes are highlighted, with emphasis on their strengths, applications, and limitations. Recommendations for future research directions are given to further enhance probe development and characterization. [ABSTRACT FROM AUTHOR]

Numerous compounds that are scavengers of hydroxyl radicals (•OH) in Fenton systems have low solubility in water. Therefore, they are dissolved in organic solvents to reach suitable concentrations in the reaction milieu of the Fenton system. However, these solvents may react with •OH and iron, leading to significant errors in the results. We evaluated 11 solvents (4 alcohols, acetone, 4 esters, dimethyl-sulfoxide, and acetonitrile) at concentrations ranging from 0.105 µmol/L to 0.42 µmol/L to assess their effects on light emission, a recognized measure of •OH radical activity, in the Fe2+-EGTA-H2O2 system. Six solvents inhibited and four solvents enhanced light emission at all tested concentrations. Acetonitrile, which initially suppressed light emission, lost this effect at a concentration of 0.105 µmol/L, (−1 ± 13 (2; 0) %, p > 0.05). Methanol, at the lowest tested concentration, inhibited light emission by 62 ± 4% (p < 0.05), while butyl butyrate enhanced it by 93 ± 16% (p < 0.05). These effects may be explained by solvent-driven •OH-scavenging, inhibition or acceleration of Fe2+ regeneration, or photon emission from excited solvent molecules. Our findings suggest that acetonitrile seems suitable for preparing stock solutions to evaluate antioxidant activity in the Fe2+-EGTA-H2O2 system, provided that the final concentration of this solvent in the reaction milieu is kept below 0.105 µmol/L. [ABSTRACT FROM AUTHOR]

Antimicrobial blue light (aBL) has become a promising non-invasive method that uses visible light, typically within the 405–470 nm wavelength range, to efficiently inactivate a wide variety of pathogens. However, the mechanism of antimicrobial blue light (aBL) has not been fully understood. In this study, our research group investigated the sensitivity of Escherichia coli BW25113 single-gene deletion mutants to individual stressors generated by aBL. Sixty-four aBL-sensitive mutants were tested under conditions mimicking the stress generated by irradiation with aBL, with their growth defects compared to the wild-type strain. Results revealed no positive correlation between aBL and single stressors, indicating that aBL's effectiveness is due to the simultaneous generation of multiple stressors. This multifactorial effect suggests that aBL targets microbial cells more precisely than single stressors such as hydrogen peroxide. No single gene knockout conferred specific resistance, highlighting aBL's potential as an antimicrobial strategy. [ABSTRACT FROM AUTHOR]

Batch heterogeneous catalytic ozonation experiments were performed using commercial and synthesized nanoparticles as catalysts in aqueous ozone. The transferred ozone dose (TOD) ranged from 0 to 150 μM, and nanoparticles were added in concentrations between 0 and 1.5 g L−1, with all experiments conducted at 20 °C and a total volume of 240 mL. A Ce-doped TiO2 catalyst (1% molar ratio of Ce/Ti) was synthesized via the sol–gel method. Response surface methodology (RSM) was applied to identify the most significant factors affecting the removal of selected pharmaceuticals, with TOD emerging as the most critical variable. Higher TOD resulted in greater removal efficiencies. Furthermore, it was found that the commercially available metal oxides α-Al2O3, Mn2O3, TiO2, and CeO2, as well as the synthesized CeTiOx, did not increase the catalytic activity of ozone during the degradation of ibuprofen (IBF) and para-chlorobenzoic acid (pCBA). Carbamazepine (CBZ) and diclofenac (DCF) are compounds susceptible to ozone oxidation, thus their complete degradation at 150 μM transferred ozone dose was attained. The limited catalytic effect was attributed to the rapid consumption of ozone within the first minute of reaction, as well as the saturation of catalyst active sites by water molecules, which inhibited effective ozone adsorption and subsequent hydroxyl radical generation (●OH). [ABSTRACT FROM AUTHOR]

Polychlorinated naphthalenes (PCNs) are a new type of persistent organic pollutant (POP) characterized by persistence, bioaccumulation, dioxin-like toxicity, and long-range atmospheric transport. Focusing on one type of PCN, monochlorinated naphthalenes (CN-1, CN-2), this study aimed to examine their photodegradation in the environment. In this work, CN-1 and CN-2 were employed as the model pollutants to investigate their photodegradation process under UV-C irradiation. Factors like the pH, initial concentrations of CN-1, and inorganic anions were investigated. Next, the roles of hydroxyl radicals (•OH), superoxide anion radicals (O2•−), and singlet oxygen (1O2) in the photodegradation process were discussed and proposed via theory computation. The results show that the photodegradation of CN-1 and CN-2 follows pseudo-first-order kinetics. Acidic conditions promote the photodegradation of CN-1, while the effects of pH on the photodegradation of CN-2 are not remarkable. Cl−, NO3−, and SO32− accelerate the photodegradation of CN-1, whereas the effect of SO42− and CO32− is not significant. Additionally, the contributions of •OH and O2•− to the photodegradation of CN-1 are 20.47% and 38.80%, while, for CN-2, the contribution is 16.40% and 16.80%, respectively. Moreover, the contribution of 1O2 is 15.7%. Based on DFT calculations, C4 and C6 of the CN-1 benzene ring are prioritized attack sites for •OH, while C2 and C9 of CN-2 are prioritized attack sites. [ABSTRACT FROM AUTHOR]

Heterogeneous Advanced Oxidation Processes (H-AOPs) are considered a new process for removing emerging pollutants. In this case, the high reactivity of hydroxyl radicals is used to degrade persistent organic pollutants. This review explores the state-of-the-art catalyst for hydroxyl radical generation in AOPs. As a parasite reaction, chloride ions appear in alkaline conditions and compete with the active sites. The theoretical foundation of catalyst performance is explored, focusing on the fundamental principles that govern the efficiency and mechanism of hydroxyl or chloride radical production. The synthesis and electronic modification sections explore the modifications of catalysts. It discusses key methodologies for catalyst preparation, with a particular emphasis on electronic modification that enhances both activity and stability. Finally, laboratory and pilot applications highlight the effectiveness of novel or modified catalysts in different scenarios. These last findings provide insights into the future directions for research and application, aiming to draw attention to the gap between laboratory studies and real-world implementations. [ABSTRACT FROM AUTHOR]

A Fe2+-EGTA(ethylene glycol-bis (β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid)-H2O2 system emits photons, and quenching this chemiluminescence can be used for determination of anti-hydroxyl radical (•OH) activity of various compounds. The generation of •OH and light emission due to oxidative damage to EGTA may depend on the buffer and pH of the reaction milieu. In this study, we evaluated the effect of pH from 6.0 to 7.4 (that may occur in human cells) stabilized with 10 mM phosphate buffer (main intracellular buffer) on a chemiluminescence signal and the ratio of this signal to noise (light emission from medium alone). The highest signal (4698 ± 583 RLU) and signal-to-noise ratio (9.7 ± 1.5) were noted for pH 6.6. Lower and higher pH caused suppression of these variables to 2696 ± 292 RLU, 4.0 ± 0.8 at pH 6.2 and to 3946 ± 558 RLU, 5.0 ± 1.5 at pH 7.4, respectively. The following processes may explain these observations: enhancement and inhibition of •OH production in lower and higher pH; formation of insoluble Fe(OH)3 at neutral and alkaline environments; augmentation of •OH production by phosphates at weakly acidic and neutral environments; and decreased regeneration of Fe2+-EGTA in an acidic environment. Fe2+-EGTA-H2O2 system in 10 mM phosphate buffer pH 6.6 seems optimal for the determination of anti-•OH activity. [ABSTRACT FROM AUTHOR]

The lack of vertical observation of reactive nitrogen oxides in agricultural areas has posed a significant challenge in fully understanding their sources and impacts on atmospheric oxidation. Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations were conducted in the agricultural regions of the North China Plain (NCP) during the summer of 2019 to measure the vertical distributions of aerosols, nitrogen dioxide (NO2), and nitrous acid (HONO). This study aimed at revealing the spatiotemporal distribution, sources, and environmental effects of reactive nitrogen oxides in the NCP agricultural areas. Our findings indicated that the vertical profiles of aerosols and NO2 exhibited a near-Gaussian distribution, with distinct peak times occurring between 8:00–10:00 and 16:00–18:00. HONO reached its maximum concentration near the surface around 8:00 in the morning and decreased exponentially with altitude. After sunrise, the concentration of HONO rapidly decreased due to photolysis. Additionally, the potential source contribution function (PSCF) was used to evaluate the potential sources of air pollutants. The results indicated that the main potential pollution sources of aerosols were located in the southern part of the Hebei, Shanxi, Shandong, and Jiangsu provinces, while the potential pollution sources of NO2 were concentrated in the Beijing–Tianjin–Hebei region. At altitudes exceeding 500 m, the heterogeneous reactions of NO2 on aerosol surfaces were identified as one of the important contributors to the formation of HONO. Furthermore, we discussed the production rate of hydroxyl radicals (OH) from HONO photolysis. It was found that the production rate of OH from HONO photolysis decreased with altitude, with peaks occurring in the morning and late afternoon. This pattern was consistent with the variations in HONO concentration, indicating that HONO was the main contributor to OH production in the agricultural regions of the NCP. This study provides a new perspective on the sources of active nitrogen in agricultural regions and their contribution to atmospheric oxidation capacity from a vertical perspective. [ABSTRACT FROM AUTHOR]

Herein, this study has examined the influence of Zn2+ sources during a biogenic-mediated pathway to synthesize ZnO nanoparticles with highly desirable solar-responsive catalytic properties. Salts of nitrate, acetate and chloride have been utilized. The ZnO powders underwent characterization using diverse analytical tools, including XRD, FTIR, Raman, BET, SEM, TEM with EDS/elemental mapping and UV-vis absorption/emission spectroscopic analyses. Accordingly, precursors have proved to affect crystallinity, morphology, surface characteristics, optical properties and the photocatalytic degradation of methylene blue (MB) model pollutant. It was observed that ZnO derived from zinc acetate precursor (Z-AC NPs) exhibits very fast photocatalytic degradation of MB at pH 11 with superior kinetic estimates of 0.314 min−1 and t1/2 = 2.2 min over many of recent reports. In contrast, the chloride precursor is not recommended along with the employed biogenic route. The intriguing findings could be directly correlated to the decreased crystal size, augmented surface area, the hexagonal morphology of the crystals, high potency in absorbing visible photons, high efficacy in separating photogenerated charge carriers and producing high amounts of •OH radicals. Further testing of Z-AC NPs in photocatalytic remediation of water samples from Dumat Aljandal Lake in Aljouf, Saudi Arabia, contaminated with MB and pyronine Y (PY) dyestuffs, showed high dye photodegradation. Therefore, this work could lead to an extremely fast avenue for decontaminating wastewater from hazmat dyestuff. [ABSTRACT FROM AUTHOR]

The removal of persistent organic micropollutants (OMPs) from secondary effluent in wastewater treatment plants is critical for meeting water reuse standards. Traditional treatment methods often fail to adequately degrade these contaminants. This study explored the efficacy of a hybrid ozonation membrane filtration (HOMF) process using CeO2 and CeTiOx-doped ceramic crossflow ultrafiltration ceramic membranes for the degradation of OMPs. Hollow ceramic membranes (CM) with a 300 kDa molecular weight cut-off (MWCO) were modified to serve as substrates for catalytic nanosized metal oxides in a crossflow and inside-out operational configuration. Three types of depositions were tested: a single layer of CeO2, a single layer of CeTiOx, and a combined layer of CeO2 + CeTiOx. These catalytic nanoparticles were distributed uniformly using a solution-based method supported by vacuum infiltration to ensure high-throughput deposition. The results demonstrated successful infiltration of the metal oxides, although the yield permeability and transmembrane flow varied, following this order: pristine > CeTiOx > CeO2 > CeO2 + CeTiOx. Four OMPs were examined: two easily degraded by ozone (carbamazepine and diclofenac) and two recalcitrant (ibuprofen and pCBA). The highest OMP degradation was observed in demineralized water, particularly with the CeO2 + CeTiOx modification, suggesting O3 decomposition to hydroxyl radicals. The increased resistance in the modified membranes contributed to the adsorption phenomena. The degradation efficiency decreased in secondary effluent due to competition with the organic and inorganic load, highlighting the challenges in complex water matrices. [ABSTRACT FROM AUTHOR]

This paper studies the dynamics of the development of laser breakdown plasma in aqueous colloids of dysprosium nanoparticles by analyzing the time patterns of plasma images obtained using a high-speed streak camera. In addition, the distribution of plasma flashes in space and their luminosity were studied, and the amplitude of acoustic signals and the rate of generation of new chemical products were studied depending on the concentration of dysprosium nanoparticles in the colloid. Laser breakdown was initiated by pulsed radiation from a nanosecond Nd:YAG laser. It is shown that the size of the plasma flash, the speed of motion of the plasma–liquid interface, and the lifetime of the plasma flash decrease with an increasing concentration of nanoparticles in the colloid. In this case, the time delay between the beginning of the laser pulse and the moment the plasma flash reaches its maximum intensity increases with increasing concentrations of nanoparticles. Varying the laser fluence in the range from 67 J/cm2 to 134 J/cm2 does not lead to noticeable changes in these parameters, due to the transition of the breakdown plasma to the critical regime. For dysprosium nanoparticles during laser breakdown of colloids, a decrease in the yield of hydrogen peroxide and an increase in the rate of formation of hydroxyl radicals per water molecule, characteristic of nanoparticles of rare earth metals, are observed, which may be due to the participation of nanoparticles and hydrogen peroxide in reactions similar to the Fenton and Haber–Weiss reactions. [ABSTRACT FROM AUTHOR]

Nitrogen oxide (NOx) pollutants have a significant impact on both the environment and human health. Photocatalytic NOx removal offers a sustainable and eco-friendly approach to combatting these pollutants by harnessing renewable solar energy. Photocatalysis demonstrates remarkable efficiency in removing NOx at sub-scale levels of parts per billion (ppb). The effectiveness of these catalysts depends on various factors, including solar light utilization efficiency, charge separation performance, reactive species adsorption, and catalytic reaction pathway selectivity. Moreover, achieving high stability and efficient photocatalytic activity necessitates a multifaceted materials design strategy. This strategy encompasses techniques such as ion doping, defects engineering, morphology control, heterojunction construction, and metal decoration on metal- or metal oxide-based photocatalysts. To optimize photocatalytic processes, adjustments to band structures, optimization of surface physiochemical states, and implementation of built-in electric field approaches are imperative. By addressing these challenges, researchers aim to develop efficient and stable photocatalysts, thus contributing to the advancement of environmentally friendly NOx removal technologies. This review highlights recent advancements in photocatalytic NOx removal, with a focus on materials design strategies, intrinsic properties, fundamental developmental aspects, and performance validation. This review also presents research gaps, emphasizing the need to understand the comprehensive mechanistic photocatalytic process, favored conditions for generating desired reactive species, the role of water concentration, temperature effects, inhibiting strategies for photocatalyst-deactivating species, and the formation of toxic NO2. [ABSTRACT FROM AUTHOR]

Among pollution remediation technologies, advanced oxidation processes (AOPs) are genuinely efficient since they are based on the production of strong, non-selective oxidants, mainly hydroxyl radicals (·OH), by a set of physicochemical methods. The biological counterparts of AOPs, which may be referred to as advanced bio-oxidation processes (ABOPs), have begun to be investigated since the mechanisms of induction of ·OH production in fungi are known. To contribute to the development of ABOPs, advanced oxidation of a wide number of dyes by the white-rot fungus Pleurotus eryngii, via a quinone redox cycling (QRC) process based on Fenton's reagent formation, has been described for the first time. The fungus was incubated with 2,6-dimethoxy-1,4-benzoquinone (DBQ) and Fe3+-oxalate, with and without Mn2+, leading to different ·OH production rates, around twice higher with Mn2+. Thanks to this process, the degradative capacity of the fungus increased, not only oxidising dyes it was not otherwise able to, but also increasing the decolorization rate of 20 dyes by more than 7 times in Mn2+ incubations. In terms of process efficacy, it is noteworthy that with Mn2+ the degradation of the dyes reached values of 90–100% in 2–4 h, which are like those described in some AOPs based on the Fenton reaction. [ABSTRACT FROM AUTHOR]

The use of an ozonized bubble column reactor (OBCR) in wastewater treatment is advantageous due to its efficient mixing and mass transfer characteristics. Among all high-performance features, the ozonation reaction in a BCR undergoes a low dissolution of O3 in the reactor with a limited reaction rate. In this study, the ozonation reaction of phenol in an OBCR was tested using a ZnO nanocatalyst and alumina balls as packing material. Three concentrations of O3 were evaluated (i.e., 10, 15, and 20 ppm), and 20 ppm was found to be the optimum concentration for phenol degradation. Also, two doses (i.e., 0.05 and 0.1 g/L) of ZnO nanocatalysts were applied in the reaction mixture, with the optimal dose found to be 0.1 g/L. Accordingly, three phenol concentrations were investigated in the OBCR (i.e., 15, 20, and 25 ppm) using four treatment methods (i.e., O3 alone, O3/Al2O3, O3/ZnO nanocatalyst, and O3/Al2O3/ZnO nanocatalyst). At a contact time of 60 min and phenol concentration of 15 ppm, the removal rate was 66.2, 73.1, 74.5, and 86.8% for each treatment method, respectively. The treatment experiment that applied the O3/Al2O3/ZnO nanocatalyst produced the highest phenol conversion into CO2 and H2O in the shortest contact time for all phenol concentrations. Thus, the OBCR employed with a ZnO nanocatalyst plus packing material is a promising technology for the rapid and active removal of phenol because it enhances the number of hydroxyl radicals (•OH) generated, which ultimately increases the oxidation activity in the OBCR. Also, the results showed efficient flow characteristics in the OBCR, with channeling problems averted due to appropriate gas movement resulting from the use of packing materials. Finally, it was found that the ozonation process in an OBCR is an efficient method for phenol conversion with good economic feasibility. [ABSTRACT FROM AUTHOR]

The aim of this study is to propose a successful method for the treatment of water contaminated by pharmaceutical pollutants through homogeneous photocatalysis in the presence of decatungstate ions (W10O324−). Sulfamethazine (SMZ), a sulfonamide antibiotic, was used as a model molecule. The results showed that SMZ could be effectively degraded with this process under simulated solar irradiation. SMZ degradation kinetics were studied with different dioxygen and SMZ concentrations, pH values, and photocatalyst masses. Optimal conditions were determined to be pH 7, [Na4W10O32] = 0.33 g/L, and [SMZ] = 13.9 mg/L under the aerated condition, resulting in 85% SMZ degradation in 240 min, using a 36W-UVA/UVB light source. Hydroxyl radicals were identified as the major contributors to SMZ elimination. Four photoproducts identified with high-performance liquid chromatography coupled with mass spectrometry were formed by the cleavage of the sulfonamide bond and the hydroxylation of both the aromatic ring and pyrimidine moiety. SMZ was completely mineralized after 90 h of irradiation in the presence of decatungstate anions. These results provided a mechanism for the photocatalytic degradation of SMZ in an aqueous solution. To sustain this mechanism, theoretical studies were carried out using density functional theory calculations. This involved Fukui functional analyses, including ring hydroxylation, C-S bond cleavage, and molecular rearrangement processes. [ABSTRACT FROM AUTHOR]

Two analytical methods previously developed by our groups were employed to estimate the antioxidant capacity of commercial fruit juices. The electrochemical method, which measures the scavenging activity of antioxidants towards OH radicals generated by both hydrogen peroxide photolysis and Fenton's reaction, is based on the recovery of the cyclic voltametric response of the redox probe Ru(NH3)63+ at a Glassy Carbon electrode modified with a thin film of an insulating polyphenol, in the presence of compounds with antioxidant properties. The values of the antioxidant capacity of the fruit juices are expressed as vitamin C equivalents/L. The chromatographic method is based on the generation of OH radicals via Fenton's reaction in order to test the inhibition of their formation in the presence of antioxidant compounds by monitoring salicylate aromatic hydroxylation derivatives as markers of •OH production, by means of HPLC coupled to coulometric detection. The results are expressed as the percentage of inhibition of •OH production in the presence of the tested juice compared to the control sample. When OH radicals are produced by Fenton's reaction, the antioxidant capacity of the juices, estimated by both methods, displays an analogous trend, confirming that they can be considered an alternative for measuring the ability of antioxidants to block OH radical formation. [ABSTRACT FROM AUTHOR]

Nanosized Ag and CeO2 particles obtained through the hydrothermal method were physically mixed to obtain composite antibacterial agents. The comparative experiments of antibacterial properties showed that the antibacterial activity of the nanocomposites was improved compared to the nanoparticles alone, which indicated that the synergistic antibacterial effect existed between Ag and CeO2. On the one hand, ICP-MS results showed that the existence of CeO2 suppressed the silver ion release rate and provided the composite with the ability of antibrowning; on the other, EPR data indicated that more hydroxyl radicals (·OH) were generated by the interfacial interaction between nanosized Ag and nanosized CeO2. Hence, for the Ag-CeO2 composite antibacterial agent, hydroxyl radicals played an important role in causing bacterial death. [ABSTRACT FROM AUTHOR]

It has been well known for a long time that inert gases, such as xenon (Xe), have significant biological effects. As these atoms are extremely unlikely to partake in direct chemical reactions with biomolecules such as proteins, lipids, and nucleic acids, there must be some other mode of action to account for the effects reported. It has been shown that the topology of proteins allows for cavities and hydrophobic pockets, and it is via an interaction with such protein structures that inert gases are thought to have their action. Recently, it has been mooted that the relatively inert gas molecular hydrogen (H2) may also have its effects via such a mechanism, influencing protein structures and actions. H2 is thought to also act via interaction with redox active compounds, particularly the hydroxyl radical (·OH) and peroxynitrite (ONOO−), but not nitric oxide (NO·), superoxide anions (O2·−) or hydrogen peroxide (H2O2). However, instead of having a direct interaction with H2, is there any evidence that these redox compounds can also interact with Xe pockets and cavities in proteins, either having an independent effect on proteins or interfering with the action of inert gases? This suggestion will be explored here. [ABSTRACT FROM AUTHOR]

The paper investigates the physicochemical processes that occur during laser-induced breakdown in colloids of gadolinium oxide nanoparticles of different concentrations. A monotonic change in the number of optical breakdowns, the average distance between the nearest breakdowns in the track of a single laser pulse, the average plasma size of a single optical breakdown, the integral luminosity of an optical breakdown plasma flash, the intensity of acoustic signals, and the rate of formation of dissociation products—O2, H2, OH•, and H2O2—is demonstrated. It is shown that the rate of formation of chemical products of the decomposition of H2O molecules under the action of breakdown when using nanoparticles of rare earth metals, in particular, gadolinium oxide, is the highest compared to other materials. Based on one laser pulse, the rates of formation of chemical products formed during the dissociation of water during laser-induced breakdown of a colloid of gadolinium oxide nanoparticles are 13.13 nmol/pulse for H2, 5.41 nmol/pulse for O2, and 6.98 nmol/pulse for hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The fluoroquinolone-type antibiotic ofloxacin is regularly detected in wastewaters. In this work, its hydroxyl radical (•OH) induced degradation was studied at a concentration of 0.1 mmol dm−3 in three water matrices, pure water, tap water, and purified wastewater (collected from a wastewater treatment plant). •OH was produced by γ-irradiation under conditions when it had a high yield. The •OH dosage dependencies of chemical (COD) and biochemical (BOD) oxygen demands, total organic carbon (TOC) content, oxygen uptake rate (OUR), Microtox® toxicity, and antibacterial activity values were evaluated. •OH effectively oxidized and mineralized ofloxacin; both processes were observed even at the lowest •OH dosage, 0.14 mmol dm−3 (0.5 kGy absorbed dose). When 0.28 mmol dm−3 •OH was introduced into pure or tap water, the antibacterial activity vanished. In purified wastewater, a higher dosage (0.56 mmol dm−3) was required to achieve the same effect as in pure water, due to the organic molecules of the matrix that quenched the •OH radicals. The products did not have antibacterial activity and showed little toxicity toward the test organism Vibrio fischeri. •OH preferentially attacks the pharmacophore part, the 4-quinolone unit of ofloxacin. •OH-induced reactions can be safely applied to destroy the antimicrobial potency of fluoroquinolone-type antibiotics in purified wastewater matrices. [ABSTRACT FROM AUTHOR]

The sonolysis of certain substrates in water has proved its effectiveness for the enhancement of the sonochemical production of hydrogen. In this study, the sonolysis of methane has been investigated for the first time in a single acoustic bubble (microreactor) over a frequency from 140 to 515 kHz. The obtained findings have been compared to those available in the literature. Independently of the methane dose (inside the bubble), the yield of H2 was improved especially with the decrease in wave frequency (from 515 to 140 kHz). For the driving frequencies 140, 213, 355, and 515 kHz, the production of hydrogen was maximized at 20, 15, 10, and 10% CH4, respectively. For 213 kHz, and the presence of 10% methane, the yield of hydrogen goes up by 111 fold compared to the case where the gas atmosphere is saturated only by argon. On the other hand, the highest methane conversions (~100% for 2, 5 and 7% CH4) were retrieved at 140 and 213 kHz. In terms of hydrogen formation and methane decay, the use of 140 kHz was found to be the best choice, whereas for a multi-bubble system, the number of acoustic bubbles should be taken into account for an optimal choice of frequency. Interestingly, it was observed that at 140 and 213 kHz and for methane mole fractions lower than or equal to 30 and 10%, respectively, a maximal formation of H2 and a relatively important production of •OH could result simultaneously. [ABSTRACT FROM AUTHOR]

Fenton (H2O2/Fe2+) system is a simple and efficient advanced oxidation technology (AOT) for the treatment of organic micropollutants in water and soil. However, it suffers from some drawbacks including high amount of the catalyst, acid pH requirement, sludge formation and slow regeneration of Fe2+ ions. If these drawbacks are surmounted, Fenton system can be the best choice AOT for the removal of persistent organics from water and soil. In this work, it was attempted to replace the homogeneous catalyst with a heterogeneous natural iron-based catalyst for the decomposition of H2O2 into oxidative radical species, mainly hydroxyl (HO•) and hydroperoxyl radicals (HO2•). The natural iron-based catalyst is hematite-rich (α-Fe2O3) and contains a nonnegligible amount of magnetite (Fe3O4) indicating the coexistence of Fe (III) and Fe(II) species. A pseudo-first order kinetics was determined for the decomposition of H2O2 by the iron-based solid catalyst with a rate constant increasing with the catalyst dose. The catalytic decomposition of H2O2 into hydroxyl radicals in the presence of the natural Fe-based catalyst was confirmed by the hydroxylation of benzoic acid into salicylic acid. The natural Fe-based catalyst/H2O2 system was applied for the degradation of riluzole in water. It was demonstrated that the smaller the particle size of the catalyst, the larger its surface area and the greater its catalytic activity towards H2O2 decomposition into hydroxyl radicals. The degradation of riluzole can occur at all pH levels in the range 3.0–12.0 with a rate and efficiency greater than H2O2 oxidation alone, indicating that the natural Fe-based catalyst can function at any pH without the need to control the pH by the addition of chemicals. An improvement in the efficiency and kinetics of the degradation of riluzole was observed under UV irradiation for both homogeneous and heterogeneous Fenton systems. The results chromatography analysis demonstrate that the degradation of riluzole starts by the opening of the triazole ring by releasing nitrate, sulfate, and fluoride ions. The reuse of the catalyst after heat treatment at 500 °C demonstrated that the heat-treated catalyst retained an efficiency >90% after five cycles. The results confirmed that the natural sources of iron, as a heterogeneous catalyst in a Fenton-like system, is an appropriate replacement of a Fe2+ homogeneous catalyst. The reuse of the heterogeneous catalyst after a heat-treatment represents an additional advantage of using a natural iron-based catalyst in Fenton-like systems. [ABSTRACT FROM AUTHOR]

This study investigated the broad-spectrum bactericidal activity of non-electrolytic hypochlorite water (NEHW) and detected its hydroxyl radical content compared with that of slightly acidic electrolytic water (SAEW). Based on the results of UV scanning and storage stability, higher hypochlorite content and stronger oxidation were found to be responsible for the stronger bactericidal effect of NEHW. NEHW can achieve 99% bacterial disinfection effect by treating with 10 mg/L available chlorine concentration for more than 5 minutes. At the same time, the storage stability of NEHW was higher than that of SAEW. After 20 days of storage under sealed and dark conditions, the pH value only increased by 7.9%, and the effective chlorine concentration remained nearly 80%. The results showed that NEHW had higher germicidal efficacy and storage stability than SAEW. [ABSTRACT FROM AUTHOR]

The ozone/peroxymonosulfate (O3/PMS) system has attracted widespread attention from researchers owing to its ability to produce hydroxyl radicals (•OH) and sulfate radicals (SO4•−) simultaneously. The existing research has shown that the O3/PMS system significantly degrades refinery trace organic compounds (TrOCs) in highly concentrated organic wastewater. However, there is still a lack of systematic understanding of the O3/PMS system, which has created a significant loophole in its application in the treatment of highly concentrated organic wastewater. Hence, this paper reviewed the specific degradation effect, toxicity change, reaction mechanism, various influencing factors and the cause of oxidation byproducts (OBPs) of various TrOCs when the O3/PMS system is applied to the degradation of highly concentrated organic wastewater. In addition, the effects of different reaction conditions on the O3/PMS system were comprehensively evaluated. Furthermore, given the limited understanding of the O3/PMS system in the degradation of TrOCs and the formation of OBPs, an outlook on potential future research was presented. Finally, this paper comprehensively evaluated the degradation of TrOCs in highly concentrated organic wastewater by the O3/PMS system, filling the gaps in scale research, operation cost, sustainability and overall feasibility. [ABSTRACT FROM AUTHOR]

Herein, we have synthesized different BWO samples at different temperatures and evaluated their electrochemical oxidation of Rhodamine B dye in an aqueous medium. The prepared samples were characterized using X-ray diffraction combined with Rietveld refinements, scanning electron microscope coupled with energy dispersive elemental mapping, and thermogravimetric and differential thermal analyses. All the samples crystallize in the orthorhombic Pca21 structure. The crystallite size increased with temperature. The calculated surface areas from the XRD data ranged from 38 to 7 m2 g−1 for BWO-600 to BWO-900, respectively. The optimal BWO loadings on the GCE electrode were 5 × 10−8 mol cm−2 recording the best electrocatalytic efficiency for RhB electrodegradation in 15 min (100%) in 0.1 M of NaCl. The BWO-600 recorded the best activity compared to other BWO samples. The electrocatalytic activity was explained by the high surface area and small crystallite size compared to the other samples. The BWO-600 showed extended electrode reutilization for up to four cycles of reuse under the reported conditions. [ABSTRACT FROM AUTHOR]

Peroxidase enzymes are crucial in analytical chemistry owing to significant peroxide analytes and their key role in hydrogen peroxide (H2O2) detection. Therefore, exploiting appropriate catalysts for the peroxidase like reactions has become crucial for achieving desired analytical performance. Zirconium (Zr) has attracted growing interest, as a safe and stable potential eco-friendly catalyst for various organic transformations that address increasing environmental challenges. Hence, aiming at fast, sensitive and selective optical detection of H2O2, a colorimetric platform is presented here, based on the excellent peroxidase enzyme-like activity of Zr decorated on graphene oxide (GO). The synergistic effect achieved due to intimate contact between an enzyme like Zr and the high surface area 0f GO ensures efficient electron transfer that increases the chemical and catalytic activity of the composite and advances the decomposition of H2O2 into hydroxyl radicals. The designed probe, thus, efficiently catalyzes the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), via hydroxyl radicals, thereby transforming the colorless TMB into blue oxidized TMB within 2 min. The catalytic mechanism of the Zr-GO enzyme mimic is proposed herein and verified using a fluorescent probe terephthalic acid (TA) and other scavenger experiments. The multifunctional optical probe allows sensitive and highly selective recognition of H2O2 in a linear range from 100 to 1000 µM with a low detection limit of 0.57 µM. Essentially, the direct accessibility of Zr prevents having to use the complicated preparation and purification procedures mostly practiced for conventional biozymes and nanozymes. The devised method offers several gains, including being green and an inexpensive catalyst, having lower LOD, being fast, cost-effective and sensitive, and having selective work-up procedures. [ABSTRACT FROM AUTHOR]

In recent years, due to the abuse of pharmaceuticals and personal care products (PPCPs), many refractory trace organic compounds (TrOCs) have been transferred into natural water bodies, posing significant challenges to the water environment. On the other hand, advanced oxidation processes (AOPs) are cleaner and more efficient than traditional biochemical degradation processes. Among them, the combined ozone/persulfate advanced oxidation process (O3/PMS) based on sulfate radicals (SO4•−) and hydroxyl radicals (•OH) has developed rapidly in recent years. Thus, this paper summarised the reaction mechanism of O3/PMS and analysed its research and application progress in drinking water treatment. In addition, the process's operation characteristics and current application scope were discussed, and the generation ways and inhibition methods of bromate and halogenates, by-products in the oxidation process, were summarised, which had a specific reference value for further research on O3/PMS process. [ABSTRACT FROM AUTHOR]

The uncontrolled growth of harmful algal blooms (HABs) can negatively impact the environment and pose threats to human health and aquatic ecosystems. Titanium dioxide (TiO2) is known to be effective in killing harmful algae through flocculation and sedimentation. However, TiO2 in a dispersed form can harm other non-target marine organisms, which has raised concerns by environmentalists and scientists. This research seeks to explore the utility of immobilized titanium oxide as a photocatalyst for mitigation of HABs, where the Alexandrium minutum bloom was used as a model system herein. Chitosan was modified with 0.2 wt.% TiO2 (Chi/TiO2 (x mL; x = 1, 3 and 5 mL) and the corresponding films were prepared via solvent casting method. Scanning electron microscope (SEM) images of the films reveal a highly uneven surface. X-ray diffraction (XRD) analysis indicates the reduction in chitosan crystallinity, where the presence of TiO2 was negligible, in accordance with its dispersion within the chitosan matrix. The photocatalytic mitigation of A.minutum was carried out via a physical approach in a laboratory-scale setting. The negative surface charge of the films was observed to repel the negatively charged A.minutum causing fluctuation in the removal efficiency (RE). The highest RE (76.1 ± 13.8%) was obtained when Chi/TiO2 (1 mL) was used at 72 h, where the hydroxyl radicals generated were inferred to contribute to the deactivation of the algae cells by causing oxidative stress. An outcome of this study indicates that such hybrid films have the potential to replace the non-immobilized (dispersed) TiO2 for HAB mitigation. However, further investigation is required to deploy these films for field applications at a larger scale. [ABSTRACT FROM AUTHOR]

Cu and Co have shown superior catalytic performance to other transitional elements, and layered double hydroxides (LDHs) have presented advantages over other heterogeneous Fenton catalysts. However, there have been few studies about Co–Cu LDHs as catalysts for organic degradation via the Fenton reaction. Here, we prepared a series of Co–Cu LDH catalysts by a co-precipitation method under different synthesis temperatures and set Rhodamine B (RhB) as the target compound. The structure-performance relationship and the influence of reaction parameters were explored. A study of the Fenton-like reaction was conducted over Co–Cu layered hydroxide catalysts, and the variation of synthesis temperature greatly influenced their Fenton-like catalytic performance. The Co–Cut=65°C catalyst with the strongest LDH structure showed the highest RhB removal efficiency (99.3% within 30 min). The change of synthesis temperature induced bulk-phase transformation, structural distortion, and metal–oxygen (M–O) modification. An appropriate temperature improved LDH formation with defect sites and lengthened M–O bonds. Co–Cu LDH catalysts with a higher concentration of defect sites promoted surface hydroxide formation for H2O2 adsorption. These oxygen vacancies (Ovs) promoted electron transfer and H2O2 dissociation. Thus, the Co–Cu LDH catalyst is an attractive alternative organic pollutants treatment. [ABSTRACT FROM AUTHOR]

Ibuprofen (IBU), a nonsteroidal anti-inflammatory drug, is one of the most widely used and frequently detected pharmaceuticals and personal care products in water bodies. This study examined the IBU degradation in aquatic solutions via ferric ion activated peroxydisulfate (PDS) coupled with electro-oxidation (EC/Fe3+/PDS). The degradation mechanisms involved three synergistic reactions in the EC/Fe3+/PDS system, including: (1) the electro-oxidation; (2) SO 4 • − generated from the activation of PDS by ferrous ions formed via cathodic reduction; (3) SO 4 • − generated from the electron transfer reaction. The radical scavenging experiments indicated that SO 4 • − and •OH dominated the oxidation process. The effects of the applied current density, PDS concentration, Fe3+ dosage, initial IBU concentration and initial pH as well as inorganic anions and humic acid on the degradation efficiency, were studied, and the degradation process of IBU followed the pseudo-first-order kinetic model. About 99.37% of IBU was removed in 60 min ((Fe3+ concentration) = 2.0 mM, (PDS concentration) = 12 mM, (initial IBU concentration) = 30 mg/L, current density = 15 mA/cm2, initial pH = 3). Finally, seven intermediate compounds were identified and probable IBU degradation pathways in the EC/Fe3+/PDS system were speculated. [ABSTRACT FROM AUTHOR]

In this work, the degradation of 4-ethylpyridine (4EP) in water by a heterogeneous photo-Fenton process (H2O2/Fe3O4/ultraviolet irradiation (UV)) was investigated. More rapid and effective 4EP degradation was obtained with H2O2/Fe3O4/UV than Fenton-like (H2O2/Fe3O4) and UV/H2O2, which is due to the larger production of hydroxyl radicals from the chemical and photolytic decomposition of H2O2. The operational conditions were varied during 4EP degradation experiments to evaluate the effects of pH, catalyst, concentration, and temperature on the kinetics and efficiency of H2O2/Fe3O4/UV oxidation. Under optimal conditions (100 mg/L 4EP, [H2O2] = 1000 mg/L, Fe3O4 = 40 mg/L, pH = 3 and room temperature, 300 rpm), 4EP was totally declined and more than 93% of the total organic carbon (TOC) was eliminated. Liquid chromatography analysis confirmed the formation of aromatic and aliphatic intermediates (4-hydroxypyridine, 4-pyridone, malonic, oxalic, and formic acids) that resulted in being mineralized. Ion chromatography analysis demonstrated the stoichiometric release of NH4+ ions during 4EP degradation by heterogeneous photo-Fenton oxidation. The reuse of the heterogeneous catalyst was evaluated after chemical and heat treatment at different temperatures. The heat-treated catalyst at 500 °C presented similar activity than the pristine Fe3O4. Accordingly, heterogeneous photo-Fenton oxidation can be an alternative method to treat wastewaters and groundwater contaminated with pyridine derivatives and other organic micropollutants. The combination of heterogeneous photo-Fenton oxidation with classical biological methods can be proposed to reduce the overall cost of the treatment in large-scale water treatment plants. [ABSTRACT FROM AUTHOR]

Tannic acid (TA) is a major pollutant present in the wastewater generated from vegetable tanneries process and food processing. This work studied TA degradation by two advanced oxidation processes (APOs): UV irradiation at the wavelength of 254 nm in the presence of hydrogen peroxide (H2O2) and ferrous iron (photo-Fenton) and in the presence of potassium persulfate. The influence of certain experimental parameters such as K2S2O8, H2O2, Fe2+, and TA concentrations, initial pH and temperature was evaluated in order to obtain the highest efficiency in terms of aromatics (decay in UV absorbance at 276 nm) and TOC removals. Chemical oxidation of TA (0.1 mM) by UV/persulfate achieved 96.32% of aromatics removal and 54.41% of TOC removal under optimized conditions of pH = 9 and 53.10 mM of K2S2O8 after 60 min. The treatment of TA by photo-Fenton process successfully led to almost complete aromatics removal (99.32%) and high TOC removal (94.27%) from aqueous solutions containing 0.1 mM of TA at natural pH = 3 using 29.4 mM of H2O2 and 0.18 mM of Fe2+ at 25 °C after 120 min. More efficient degradation of TA by photo-Fenton process than UV/persulfate was obtained, which confirms that hydroxyl radicals are more powerful oxidants than sulfate radicals. The complete removal of organic pollution from natural waters can be accomplished by direct chemical oxidation via hydroxyl radicals generated from photocatalytic decomposition of H2O2. [ABSTRACT FROM AUTHOR]

In this work, the degradation and mineralization of Diallyl Phthalate (DAP) in water by Fenton oxidation was investigated. The effects of different experimental parameters including the initial pH, the hydrogen peroxide (H2O2) dose, the catalyst (Fe2+) dose, the iron source, and the DAP concentration on the rate and the yield of DAP degradation by Fenton oxidation were evaluated. DAP and its intermediates were quantified by high performance liquid chromatography (HPLC) analysis and the measurement of total organic carbon (TOC) during Fenton oxidation. The results obtained confirmed that hydroxyl radicals (HO•) generated from Fenton's reaction were capable of completely eliminating DAP from water. Fenton oxidation of 100 mg/L DAP aqueous solution at pH = 3.2 required 1000 mg/L H2O2 and 50 mg/L Fe2+. Under these conditions, more than TOC removal exceeded 95% after 300 min Fenton oxidation. The competition kinetics method was used to determine an absolute rate constant of 7.26.109 M−1 s−1 for the reaction between DAP and HO• radicals. HPLC analysis showed that phthalic acid, 1,2-dihydroxybenzene, 1,2,4-trihydroxybenzene, maleic acid, formic acid and oxalic acid were the main intermediates formed during DAP degradation. Accordingly, a simple DAP degradation mechanism by the Fenton reaction was proposed. These promising results proved the potential of Fenton oxidation as a cost-effective method for the decontamination of wastewaters containing phthalates. [ABSTRACT FROM AUTHOR]

Ion channels activated by reactive oxygen species (ROS) have been found in the plasma membrane of charophyte Nitella flixilis, dicotyledon Arabidopsis thaliana, Pyrus pyrifolia and Pisum sativum, and the monocotyledon Lilium longiflorum. Their activities have been reported in charophyte giant internodes, root trichoblasts and atrichoblasts, pollen tubes, and guard cells. Hydrogen peroxide and hydroxyl radicals are major activating species for these channels. Plant ROS-activated ion channels include inwardly-rectifying, outwardly-rectifying, and voltage-independent groups. The inwardly-rectifying ROS-activated ion channels mediate Ca2+-influx for growth and development in roots and pollen tubes. The outwardly-rectifying group facilitates K+ efflux for the regulation of osmotic pressure in guard cells, induction of programmed cell death, and autophagy in roots. The voltage-independent group mediates both Ca2+ influx and K+ efflux. Most studies suggest that ROS-activated channels are non-selective cation channels. Single-channel studies revealed activation of 14.5-pS Ca2+ influx and 16-pS K+ efflux unitary conductances in response to ROS. The molecular nature of ROS-activated Ca2+ influx channels remains poorly understood, although annexins and cyclic nucleotide-gated channels have been proposed for this role. The ROS-activated K+ channels have recently been identified as products of Stellar K+ Outward Rectifier (SKOR) and Guard cell Outwardly Rectifying K+ channel (GORK) genes. [ABSTRACT FROM AUTHOR]

Nitrosamines are a group of carcinogenic chemicals that are present in aquatic environments that result from byproducts of industrial processes and disinfection products. As indirect and direct potable reuse increase, the presence of trace nitrosamines presents challenges to water infrastructures that incorporate effluent from wastewater treatment. Ultraviolet (UV) photolysis or UV-based advanced oxidation processes that produce highly reactive hydroxyl radicals are promising technologies to remove nitrosamines from water. However, complex reaction mechanisms involving radicals limit our understandings of the elementary reaction pathways embedded in the overall reactions identified experimentally. In this study, we perform quantum mechanical calculations to identify the hydroxyl radical-induced initial elementary reactions with N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine, and N-nitrosomethylbutylamine. We also investigate the UV-induced NDMA degradation mechanisms. Our calculations reveal that the alkyl side chains of nitrosamine affect the reaction mechanism of hydroxyl radicals with each nitrosamine investigated in this study. Nitrosamines with one- or two-carbon alkyl chains caused the delocalization of the electron density, leading to slower subsequent degradation. Additionally, three major initial elementary reactions and the subsequent radical-involved reaction pathways are identified in the UV-induced NDMA degradation process. This study provides mechanistic insight into the elementary reaction pathways, and a future study will combine these results with the kinetic information to predict the time-dependent concentration profiles of nitrosamines and their transformation products. [ABSTRACT FROM AUTHOR]

Laboratory batch experiments were carried out to evaluate the impacts of H2O2 and copper sulfate on M. aeruginosa PCC7820, microcystin-LR (MC-LR) and its degrading bacteria Bacillus sp., previously isolated from Hulupi Lake in Taiwan. The study shows that 3 mg·L-1 hydrogen peroxide removed only 9% M. aeruginosa within seven days of exposure, from an initial cell concentration of 2 ⨰ 106 cells/mL.With copper sulfate, a concentration of 2 mg·L-1 removed 99% M. aeruginosa cells, but showed negligible efficacy in removing 0.05 mg·L-1 MC-LR. At a higher dosage, 20 mg·L-1 H2O2 led to 40% and 95% removal, respectively for MC-LR and M. aeruginosa cells. Copper sulfate and H2O2 were both lethal to Bacillus sp. population, with mortality rate constants of k = 0.04 h-1 and 0.03 h-1 under 1 mg·L-1 copper sulfate and 5 mg·L-1 H2O2, respectively. H2O2 is competitive in terms of cost, with a capability of degrading organic compounds with the assistance of ultraviolet (UV) light, and it may be considered as an alternative algaecide to copper sulfate in reservoirs for algae growth control. [ABSTRACT FROM AUTHOR]

In the presence of transition metal ions and peroxides, polyphenols, well-known dietary antioxidants, can act as pro-oxidants. We investigated the effect of 13 polyphenols and their metabolites on oxidative degradation of deoxyribose by an •OH generating Fenton system (Fe2+-ethylenediaminetetraacetic acid (EDTA)-H2O2). The relationship between phenolics pro-oxidant/anti-oxidant effects and their molecular structure was analyzed using multivariate analysis with multiple linear regression and a backward stepwise technique. Four phenolics revealed a significant inhibitory effect on OH-induced deoxyribose degradation, ranging from 54.4% ± 28.6% (3,4-dihydroxycinnamic acid) to 38.5% ± 10.4% (catechin) (n = 6), correlating with the number of -OH substitutions (r = 0.58). Seven phenolics augmented the oxidative degradation of deoxyribose with the highest enhancement at 95.0% ± 21.3% (quercetin) and 60.6% ± 12.2% (phloridzin). The pro-oxidant effect correlated (p < 0.05) with the number of -OH groups (r = 0.59), and aliphatic substitutes (r = 0.22) and weakly correlated with the occurrence of a catechol structure within the compound molecule (r = 0.17). Selective dietary supplementation with phenolics exhibiting pro-oxidant activity may increase the possibility of systemic oxidative stress in patients treated with medications containing chelating properties or those with high plasma concentrations of H2O2 and non-transferrin bound iron. [ABSTRACT FROM AUTHOR]

Power ultrasound (US) could potentially be used in the food industry in the future. However, the extent of anthocyanin degradation by US requires investigation. Cyanidin-3-glucoside (Cy-3-glu) obtained from blueberry extracts was used as research material to investigate the effect of power ultrasound on food processing of anthocyanin-rich raw materials. The effects of ultrasonic waves on the stability of Cy-3-glu and on the corresponding changes in UV-Vis spectrum and antioxidant activity were investigated, and the mechanisms of anthocyanin degradation induced by ultrasonic waves were discussed. To explore Cy-3-glu degradation in different environments, we kept the Cy-3-glu solution treated with ultrasonic waves in four concentrations (0%, 10%, 20%, and 50%) of ethanol aqueous solutions to simulate water, beer, wine, and liquor storage environment according to the chemical kinetics method. Results show that the basic spectral characteristics of Cy-3-glu did not significantly change after power ultrasound cell crusher application at 30 °C. However, with anthocyanin degradation, the intensity of the peak for Cy-3-glu at 504 nm significantly decreased (p < 0.05). The degradation kinetics of Cy-3-glu by ultrasonic waves (200–500Wfrequency) fitted well to first-order reaction kinetics, and the degradation rate constant of Cy-3-glu under power ultrasound was considerably larger than that under thermal degradation (p < 0.05). The sensitivity of the anthocyanins of blueberry to temperature increased with increasing ethanol concentration, and the longest half-life was observed in 20% ethanol aqueous solution. [ABSTRACT FROM AUTHOR]

We developed a new method for detecting S1 nucleaseand hydroxyl radicals based on the use of water-soluble conjugated poly[9,9-bis(6,6-(N,N,N-trimethylammonium)-fluorene)-2,7-ylenevinylene -co-alt-2,5-dicyano-1,4-phenylene)] (PFVCN) and tungsten disulfide (WS2) nanosheets. Cationic PFVCN is used as a signal reporter, and single-layer WS2 is used as a quencher with a negatively charged surface. The ssDNA forms complexes with PFVCN due to much stronger electrostatic interactions between cationic PFVCN and anionic ssDNA, whereas PFVCN emits yellow fluorescence. When ssDNA is hydrolyzed by S1 nuclease or hydroxyl radicals into small fragments, the interactions between the fragmented DNA and PFVCN become weaker, resulting in PFVCN being adsorbed on the surface of WS2 and the fluorescence being quenched through fluorescence resonance energy transfer. The new method based on PFVCN and WS2 can sense S1 nuclease with a low detection limit of 5 × 10-6 U/mL. Additionally, this method is cost-effective by using affordable WS2 as an energy acceptor without the need for dye-labeled ssDNA. Furthermore, the method provides a new platform for the nuclease assay and reactive oxygen species, and provides promising applications for drug screening. [ABSTRACT FROM AUTHOR]

Semiconductor TiO2 photocatalysis has attracted much attention due to its potential application in solving the problems of environmental pollution. In this paper, thiourea (CH4N2S) modified anatase TiO2 nanorods were fabricated by calcination of the mixture of TiO2 nanorods and thiourea at 600 °C for 2 h. It was found that only N element was doped into the lattice of TiO2 nanorods. With increasing the weight ratio of thiourea to TiO2 (R) from 0 to 8, the light-harvesting ability of the photocatalyst steady increases. Both the crystallization and photocatalytic activity of TiO2 nanorods increase first and then decrease with increase in R value, and R2 sample showed the highest crystallization and photocatalytic activity in degradation of Brilliant Red X3B (X3B) and Rhodamine B (RhB) dyes under visible light irradiation (λ > 420 nm). The increased visible-light photocatalytic activity of the prepared N-doped TiO2 nanorods is due to the synergistic effects of the enhanced crystallization, improved light-harvesting ability and reduced recombination rate of photo-generated electron-hole pairs. Note that the enhanced visible photocatalytic activity of N-doped nanorods is not based on the scarification of their UV photocatalytic activity. [ABSTRACT FROM AUTHOR]

Environmentally persistent free radicals (EPFRs) are an emerging pollutant and source of oxidative stress. Samples of PM 2.5 were collected at the urban sites of Lahore in both winter and summertime of 2019. The chemical composition of PM 2.5 , EPRF concentration, OH radical generation, and risk assessment of EPFRs in PM 2.5 were evaluated. The average concentration of PM 2.5 in wintertime and summertime in Lahore is 15 and 4.6 times higher than the national environmental quality standards (NEQS) of Pakistan and WHO. The dominant components of PM 2.5 are carbonaceous species. The concentration of EPFRs and reactive oxygen species (ROS), such as OH radicals, is higher in the winter than in the summertime. The secondary inorganic ions do not contribute to the generation of OH radicals, although the contribution of SO 4 2+ , NO 3 - , and NH 4 + to the mass concentration of PM 2.5 is greater in summertime. The atmospheric EPFRs are used to evaluate the exposure risk. The EPFRs in PM 2.5 and cigarette smoke have shown similar toxicity to humans. In winter and summer, the residents of Lahore inhaled the amount of EPFRs equivalent to 4.0 and 0.6 cigarettes per person per day, respectively. Compared to Joaquin County, USA, the residents of Lahore are 1.8 to 14.5 times more exposed to EPFRs in summer and wintertime. The correlation analysis of atmospheric EPFRs (spin/m 3 ) and carbonaceous species of PM 2.5 indicates that coal combustion, biomass burning, and vehicle emissions are the possible sources of EPFRs in the winter and summertime. In both winter and summertime, metallic and carbonaceous species correlated well with OH radical generation, suggesting that vehicular emissions, coal combustion, and industrial emissions contributed to the OH radical generation. The study's findings provide valuable information and data for evaluating the potential health effects of EPFRs in South Asia and implementing effective air pollution control strategies.

The kinetics and spectral characteristics of the transients formed in the reactions of •OH and •N3 with quinoxalin-2(1H)-one (Q), its methyl derivative, 3-methylquinoxalin- 2(1H)-one (3-MeQ) and pyrazin-2-one (Pyr) were studied by pulse radiolysis in aqueous solutions at pH 7. The transient absorption spectra recorded in the reactions of •OH with Q and 3-MeQ consisted of an absorption band with λmax = 470 nm assigned to the OH-adducts on the benzene ring, and a second band with λmax = 390 nm (for Q) and 370 nm (for 3-MeQ) assigned, inter alia, to the N-centered radicals on a pyrazin-2-one ring. The rate constants of the reactions of •OH with Q and 3-MeQ were found to be in the interval (5.9–9.7) × 109 M-1·s-1 and were assigned to their addition to benzene and pyrazin-2-one rings and H-abstraction from the pyrazin-2-one nitrogen. In turn, the transient absorption spectrum observed in the reaction of •N3 exhibits an absorption band with λmax = 350 nm. This absorption was assigned to the N-centered radical on the Pyr ring formed after deprotonation of the respective radical cation resulting from one-electron oxidation of 3-MeQ. The rate constant of the reaction of •N3 with 3 MeQ was found to be (6.0 ± 0.5) × 109 M-1·s-1. Oxidation of 3-MeQ by •N3 and Pyr by •OH and •N3 confirms earlier spectral assignments. With the rate constant of the •OH radical with Pyr (k = 9.2 ± 0.2) × 109 M-1·s-1, a primary distribution of the •OH attack was estimated nearly equal between benzene and pyrazin-2-one rings. [ABSTRACT FROM AUTHOR]

Ligand-enhanced hydroxyl radical (•OH) production is an important strategy for Fe(II)-catalyzed O 2 and H 2 O 2 oxidation processes. However, the influence of the molar ratio of ligands to Fe(II) on •OH production remains elusive. This study employed citrate and inorganic dissolved Fe(II) (Fe(II) dis ) as the representative ligand and Fe(II) species, respectively, to quantify this relationship. Results showed that •OH production was highly dependent on the citrate/Fe(II) molar ratio. For instance, for the oxygenation of Fe(II) dis , the •OH accumulations were 2.0-8.5, 3.4-28.5 and 8.1-42.3 μM at low (0.25-0.5), moderate (0.5-1), and high (1-2) citrate/Fe(II) molar ratios, respectively. At low citrate/Fe(II) molar ratio (<0.5), inorganic Fe(II) dis mainly contributed to •OH production, with the increase in the citrate/Fe(II) molar ratio to a high level (1-2), Fe(II)-citrate complex turned to the electron source for •OH production. The change in Fe(II) speciation with the increase of citrate/Fe(II) molar ratio elevated •OH production. For pollutant degradation, 1 mg/L phenol was degraded by 53.6% within 40 min during oxygenation of Fe(II)-citrate system (1:1) at pH 7. Our results suggest that a moderate molar ratio of ligand/Fe(II) (0.5-1) may be optimal for Fe(II)-catalyzed O 2 and H 2 O 2 oxidation processes.