Ozonation of 47 organic micropollutants in secondary treated municipal effluents: Direct and indirect kinetic reaction rates and modelling

Micropollutants like pharmaceuticals, hormones and pesticides are still found in treated municipal wastewater. An effective way to degrade micropollutants is to use oxidants such as ozone or hydroxyl radicals. We designed an innovative experimental protocol combining batch experiments and a study of a full-scale WWTP to understand and predict the removal via ozonation of typical micropollutants present in secondary treated effluents. First, the direct and indirect ozonation of 47 organic micropollutants was scrutinized, then a model was developed and calibrated to simulate the ozone transfers and the oxidation of the selected micropollutants. The kinetic rate constants between micropollutants and ozone or hydroxyl radicals (OH^●) were determined for 47 micropollutants found in secondary treated effluent. We classified the micropollutants into low- (k_O3 between 1.50 and 4.47 × 10² L mol^-1. s^-1), medium- (k_O3 between 1.31 × 10³ and 4.92 × 10³ L mol^-1. s^-1) and high-oxidizable groups (k_O3 between 9.44 × 10⁴ and 8.18 × 10⁶ L mol^-1. s^-1) according to their reactivity with ozone, and identified the major degradation pathways for all 47 micropollutants. Micropolluants of the low- and medium-oxidizable groups were largely eliminated by the indirect pathway, at 96% and 84% on average, respectively. In contrast, micropollutants of high-oxidizable group were largely eliminated by the direct pathway, at 98% on average. The model successfully simulated the direct and indirect ozonation of the 47 micropollutants in batch experiments and confirmed the predominant pathways for each group. Finally, the model was applied to the full-scale ozonation process operated at an ozone dose ranging from 0.5 to 1.6 gO₃. gDOC^-1. The model was found to reliably simulate the ozonation-process removal efficiencies for 4 micropollutants (imidacloprid, fenofibric acid, metronidazole and ketoprofen).

Stress-dependent conformational changes of artemin: Effects of heat and oxidant

Artemin is an abundant thermostable protein in Artemia embryos and it is considered as a highly efficient molecular chaperone against extreme environmental stress conditions. The conformational dynamics of artemin have been suggested to play a critical role in its biological functions. In this study, we have investigated the conformational and functional changes of artemin under heat and oxidative stresses to identify the relationship between its structure and function. The tertiary and quaternary structures of artemin were evaluated by fluorescence measurements, protein cross-linking analysis, and dynamic light scattering. Based on the structural analysis, artemin showed irreversible substantial conformational lability in responses to heat and oxidant, which was mainly mediated through the hydrophobic interactions and dimerization of the chaperone. In addition, the chaperone-like activity of heated and oxidized artemin was examined using lysozyme refolding assay and the results showed that although both factors, i.e. heat and oxidant, at specific levels improved artemin potency, simultaneous incubation with both stressors significantly triggered the chaperone activation. Moreover, the heat-induced dimerization of artemin was found to be the most critical factor for its activation. It was suggested that oxidation presumably acts through stabilizing the dimer structures of artemin through formation of disulfide bridges between the subunits and strengthens its chaperoning efficacy. Accordingly, it is proposed that artemin probably exists in a monomer–oligomer equilibrium in Artemia cysts and environmental stresses and intracellular portion of protein substrates may shift the equilibrium towards the active dimer forms of the chaperone.

Design Strategies of Conductive Hydrogel for Biomedical Applications

Conductive hydrogel, with electroconductive properties and high water content in a three-dimensional structure is prepared by incorporating conductive polymers, conductive nanoparticles, or other conductive elements, into hydrogel systems through various strategies. Conductive hydrogel has recently attracted extensive attention in the biomedical field. Using different conductivity strategies, conductive hydrogel can have adjustable physical and biochemical properties that suit different biomedical needs. The conductive hydrogel can serve as a scaffold with high swelling and stimulus responsiveness to support cell growth in vitro and to facilitate wound healing, drug delivery and tissue regeneration in vivo. Conductive hydrogel can also be used to detect biomolecules in the form of biosensors. In this review, we summarize the current design strategies of conductive hydrogel developed for applications in the biomedical field as well as the perspective approach for integration with biofabrication technologies.

Degradation of Acetaminophen via UVA-induced advanced oxidation processes (AOPs). Involvement of different radical species: HO, SO4- and HO2/O2. Chemosphere 2020;258:127268. [PMID: 32569955 DOI: 10.1016/j.chemosphere.2020.127268]

In this work, UVA radiation that is part of solar light is taken as the irradiation source and radicals (HO, SO₄^- and HO₂/O₂^-) are generated through activation of hydrogen peroxide (H₂O₂), sodium persulfate (Na₂S₂O₈) and Bismuth catalyst (BiOCl), respectively. The distinguished performance in removing acetaminophen (ACTP), a model pharmaceutical pollutant, by these three radicals was compared for the first time. Effect of pH, halide ions concentration and interfacial mechanism have been investigated in detail. Interestingly, results show that heterogeneous UVA/BiOCl process has higher degradation efficiency than homogeneous UVA/H₂O₂ and UVA/Na₂S₂O₈ systems whatever the solution's pH. To explain these results, second order reaction rate constant (k_{radical, ACTP}) have been determined with laser flash photolysis (LFP) or radical scavenging experiments. The strongly interfacial-depended HO₂/O₂^- radicals have the lowest second order rate constant with ACTP but highest steady state concentration. BiOCl is much easier activated by UVA, and outstanding ACTP mineralization can be achieved. Combination of BiOCl and Na₂S₂O₈ exhibits synergistic effects rather than antagonism effects with H₂O₂. This study highlights the relative effective utilization of solar light through interfacial directed BiOCl photocatalysis and its synergistic effects with traditional oxidants.

Direct Radiofluorination of Arene C-H Bonds via Photoredox Catalysis Using a Peroxide as the Terminal Oxidant

Herein, we describe an organic photoredox system for direct arene C-H radiofluorination, using a peroxide oxidizing agent and LEDs as the light source. In conjunction with an optimized photocatalyst and a microtubing reactor, this system is applicable to a range of electron-rich aromatics and heteroaromatics. We also demonstrate the feasibility of C-H radiofluorination without an azeotropic drying step, which greatly simplifies the workflow of the labeling process.

Construction of Unusual Indole-Based Heterocycles from Tetrahydro-1H-pyridazino[3,4-b]indoles

Herein, we report the successful syntheses of scarcely represented indole-based heterocycles which have a structural connection with biologically active natural-like molecules. The selective oxidation of indoline nucleus to indole, hydrolysis of ester and carbamoyl residues followed by decarboxylation with concomitant aromatization of the pyridazine ring starting from tetrahydro-1H-pyridazino[3,4-b]indole derivatives lead to fused indole-pyridazine compounds. On the other hand, non-fused indole-pyrazol-5-one scaffolds are easily prepared by subjecting the same C2,C3-fused indoline tetrahydropyridazines to treatment with trifluoroacetic acid (TFA). These methods feature mild conditions, easy operation, high yields in most cases avoiding the chromatographic purification, and broad substrate scope. Interestingly, the formation of indole linked pyrazol-5-one system serves as a good example of the application of the umpolung strategy in the synthesis of C3-alkylated indoles.

Mycotoxins in Feed and Food and the Role of Ozone in Their Detoxification and Degradation: An Update

Mycotoxins are secondary metabolites produced by some filamentous fungi, which can cause toxicity in animal species, including humans. Because of their high toxicological impacts, mycotoxins have received significant consideration, leading to the definition of strict legislative thresholds and limits in many areas of the world. Mycotoxins can reduce farm profits not only through reduced crop quality and product refusal, but also through a reduction in animal productivity and health. This paper briefly addresses the impacts of mycotoxin contamination of feed and food on animal and human health, and describes the main pre- and post-harvest systems to control their levels, including genetic, agronomic, biological, chemical, and physical methods. It so highlights (i) the lack of effective and straightforward solutions to control mycotoxin contamination in the field, at pre-harvest, as well as later post-harvest; and (ii) the increasing demand for novel methods to control mycotoxin infections, intoxications, and diseases, without leaving toxic chemical residues in the food and feed chain. Thus, the broad objective of the present study was to review the literature on the use of ozone for mycotoxin decontamination, proposing this gaseous air pollutant as a powerful tool to detoxify mycotoxins from feed and food.

Efficient removal of trichloroethene in oxidative environment by anchoring nano FeS on reduced graphene oxide supported nZVI catalyst: The role of FeS on oxidant decomposition and iron leakage

The performance of trichloroethene (TCE) removal was initially investigated in sodium persulfate (SPS) or potassium monopersulfate triple salt (PMS) oxidative environment by reduced graphene oxide (rGO) supported nZVI (nZVI-rGO) catalyst and further the role of sulphur by anchoring nano FeS on nZVI-rGO (FeS@nZVI-rGO) was evaluated. The high usage of oxidants and stability of FeS@nZVI-rGO catalyst were significantly improved due to the insoluble nature of this innovative catalyst by involvement of nano FeS which limited the rapid iron loss caused by the corrosion of active sites and mitigated rapid oxidants decomposition in FeS@nZVI-rGO/SPS and FeS@nZVI-rGO/PMS systems. The tests for target contaminant removal showed that over 95 % TCE could be removed at 100 mg L^-1 FeS@nZVI-rGO and 1.2 mM SPS or 0.3 mM PMS dosages, in which over 85 % TCE could be dechlorinated. The reactive oxygen radicals (ROSs) generation mechanisms and their contribution to TCE removal were investigated through radical scavenge tests in both systems, indicating that both HO and SO₄^- were the major ROSs rather than O₂^-. In conclusion, this study revealed the well function and fundamental mechanism of this innovative catalyst by anchoring nano FeS and worth of further demonstration of this technique in TCE contaminated groundwater remediation application.

Single-step removal of Hexavalent chromium and phenol using meso zerovalent iron

Novel meso-zero valent iron (mZVI) was investigated for treating complex wastewater containing toxic heavy metal Cr⁶⁺ and organic compound phenol. This study is first of its kind illustrating coupled removal in single-step with H₂O₂ playing a major role as an oxidant and reductant. The mechanism involved was electron transfer from Fe^0/2+ to Cr⁶⁺ resulting in Fe^2+/3+ which in turn was consumed for phenol oxidation returning as Fe²⁺ into the system for further Cr⁶⁺ reduction. While comparing, single-step simultaneous removal of Cr⁶⁺ and phenol showed better performance in terms of pollutant removal, Fe^2+/3+ recurrent reaction and precipitation generation, double-tep sequential removal performed better in iron active-corrosion time. It was also observed that the entire redox cycle of Cr⁶⁺-Cr³⁺-Cr⁶⁺ was reusable for co-contaminant phenol degradation at all pH with the recurrence of Fe²⁺-Fe³⁺-Fe²⁺. The proposed technique was checked for its viability in a single batch reactor and the complex chemistry of the reactions are unfolded by conducting chemical speciation and mass balance study at every stage of reaction. The unique functioning of mZVI was proven with micro-analysis of ZVI's surface and compared with granular ZVI, cZVI. The results obtained from this study open the door for a safer and cleaner single treatment system in removing both toxic heavy metals and organic compounds from contaminated surface water, groundwater and many such industrial effluents.

Oxyresveratrol Possesses DNA Damaging Activity

Artocarpus lakoocha Wall. ex Roxb. (family: Moraceae) has been used as a traditional Thai medicine for the treatment of various parasitic diseases. This species has been reported to be the source of phytochemicals, which show potent biological activities. The objective of this study was to investigate the phytochemical profile of the extracts of the heartwood of A. lakoocha and their pro-oxidant activity in vitro. The heartwood was ground, extracted, and then chromatographic and spectroscopic analyses were carried out; oxyresveratrol was identified as the major component in the extracts. The pro-oxidant activity was investigated using DNA-nick, reactive oxygen species and reducing assays. The results showed that oxyresveratrol induced DNA damage dose-dependently in the presence of copper (II) ions. It was also found to generate reactive oxygen species (ROS) in a dose-dependent manner and reduce copper (II) to copper (I). It is concluded that oxyresveratrol is the most abundant stilbenoid in A. lakoocha heartwood. The compound exhibited pro-oxidant activity in the presence of copper (II) ions, which may be associated with its ability to act as an anticancer compound.

Simultaneous removal of NOx, SO2, and Hg from flue gas in FGD absorber with oxidant injection (NaClO2)- full-scale investigation

This article presents the results of an industrial-scale study (on 400 MW_e lignite fired unit) of simultaneous NO_x, SO₂, and Hg^T removal in FGD absorber with oxidant injection (NaClO₂) into flue gas. It was confirmed that the injection of sodium chlorite upstream the FGD (Flue Gas Desulfurization) absorber oxidize NO to NO₂, Hg⁰ to Hg²⁺, and enhancing NO_x and Hg^T removal efficiency from exhaust gas in FGD absorber. Mercury removal efficiency grows with the rise of degree of oxidation NO to NO₂ and was limited by the phenomenon of re-emission. For NO_x removal the most critical parameters is slurry pH and temperature. There was no negative effect on sulfur dioxide removal efficiency caused by oxidant injection in tested FGD absorber. Based on the data provided, NO_x and Hg^T emissions can be reduced by adjusting the FGD absorber operating parameters combined with oxidant injection.

IMPLICATIONS

The emissions of nitrogen oxides and mercury from coal combustion have great influence of environment and human health. The injection of sodium chlorite upstream the FGD absorber oxidize NO to NO₂, Hg⁰ to Hg²⁺ and enhancing NOx and HgT removal efficiency from flue gas.

Resveratrol Inhibits Oxidative Stress and Prevents Mitochondrial Damage Induced by Zinc Oxide Nanoparticles in Zebrafish (Danio rerio)

Despite their wide industrial use, Zinc oxide (ZnO) nanoparticles (NPs) exhibit a high toxic potential while concerns of their health-related risks are still present, urging additional in vivo clarification studies. Oxidative stress is recognized as the primary trigger of NP-associated toxicity, suggesting antioxidants as a promising counteractive approach. Here, we investigated the protective effect of the natural antioxidant resveratrol against ZnO NP-induced toxicity in vivo using the zebrafish model. Our findings demonstrate that resveratrol counteracts ZnO NP-induced zebrafish lethality preventing cardiac morphological and functional damage. NP-induced vascular structural abnormalities during embryonic fish development were significantly counteracted by resveratrol treatment. Mechanistically, we further showed that resveratrol inhibits ROS increase, prevents mitochondrial membrane potential dysfunction, and counteracts cell apoptosis/necrosis elicited by ZnO NP. Overall, our data provide further evidence demonstrating the primary role of oxidative stress in NP-induced damage, and highlight new insights concerning the protective mechanism of antioxidants against nanomaterial toxicity.

Theoretical insight into the degradation of p-nitrophenol by OH radicals synergized with other active oxidants in aqueous solution

The degradation of p-nitrophenol (p-NP) based on OH radicals (HO^∙), HO₂ radicals (HO₂^∙) and O₂ in aqueous solution was investigated using theoretical computational methods. The complete degradation mechanisms of reaction between p-NP and HO^∙ were explored by density functional theory (DFT) methods. The 4-nitrophenoxy radicals and 1,2-dihydroxy-4-nitrocylohexadienyl radicals are confirmed to be major intermediates of the HO^∙-initiated reactions in aqueous phase, which consistent with experimental results. The chemical structures of some products (2,4-dihydroxycyclohexa-2,4-dien-1-one and 4-nitrocyclohexa-3,5-diene-1,2-dione) which were not identified in the experiment are determined. New favorable formation channels for some intermediates were found. The primary reactions initiated by HO^∙ or HO₂^∙ with p-NP reveals that HO^∙-initiated degradation is the dominant reaction. HO₂^∙ and O₂ can enhance the degradation extent of p-NP in further reactions. Rate constants of the elementary reactions and overall rate constants were calculated. In addition, the HO^∙-initiated primary reactions in a water box of 500 water molecules were studied using Monte Carlo simulation. All the OH-addition reactions are barrierless and highly feasible. The observed dynamic reaction process is similar to the DFT calculation prediction. Furthermore, the eco-toxicity evaluation shows that important products are harmless or harmful to aquatic organisms, and are much less toxic than p-NP.

Synergistically coupling membrane electrochemical reactor with Fenton process to enhance landfill leachate treatment

Landfill leachate is challenging to treat due to its complex composition. Advanced oxidation processes such as Fenton process can be effective to treat leachate. Herein, a previously developed membrane electrochemical reactor (MER) was coupled with Fenton oxidation through providing synergistic benefits with the low solution pH, reduced organics, and ammonia removal/recovery. This two-stage coupled system reduced the leachate COD by 88%, much higher than that from the standalone Fenton process treating raw leachate. In addition, the usage of chemical reagents has been greatly reduced. At a dimensionless oxidant dose of 1.0, the coupled MER-Fenton system reduced the consumption of both FeSO₄⋅7H₂O and H₂O₂ by 39%, H₂SO₄ by 100%, and NaOH by 55%. Consequently, the sludge production was reduced by 51% in weight and 12% in volume. Despite electricity consumption by the MER, the coupled system cost $4.76 per m³ leachate less than the standalone Fenton treatment. More notably, direct Fenton oxidation removed only 21% of ammonia; in comparison the MER-Fenton system removed ammonia by 98% with the possibility for recovery at a rate of 30.6-55.2 kg N m^-3 reactor d^-1. Those results demonstrate that coupling MER with Fenton process could mitigate some inherent drawbacks of Fenton oxidation such as ineffective ammonia removal, high acid and chemical reagents dose requirements, and a large amount of sludge generation. This system may be moved towards practical applications by addressing a few challenges such as using renewable energy to power MER.

Natural attenuation method for contaminant remediation reagent delivery assessment for in situ chemical oxidation using aqueous ozone

A Monitored Natural Attenuation (MNA) assessment approach typically used for contaminant remediation feasibility assessment was developed here for remediation-reagent delivery assessment. Subsurface delivery of oxidants, such as aqueous ozone (O₃) for in situ chemical oxidation (ISCO) of groundwater contaminants, is naturally attenuated by oxidant demand and reactivity. We compared mixed reactor kinetic experiments, sand column tracer transport experiments, and reactive transport modeling and assessment methods to quantify natural attenuation kinetics, aqueous O₃ solute transport, oxidant demand kinetics, and ISCO reagent delivery limitations. Sorption of aqueous O₃ to quartz sand was observed during transport of O₃ through water-saturated porous media. Pseudo 1st order decomposition rate constants of O₃ bulk attenuation with transport were comparable to mixed reactor experiments without transport, and reactive transport modeling of miscible-displacement column experiments was used to quantify each attenuation process. Aqueous ionic strength was correlated with O₃ decomposition rate constants, which was the dominant reagent delivery attenuation process. These results suggest that aqueous O₃ decomposition and oxidant delivery attenuation can be predictable upon characterization of the sediment oxidant demand and dispersion, and increasing groundwater velocity during aqueous O₃ injection can maximize transport distance for reagent delivery.

Two new predictors combined with quantum chemical parameters for the selection of oxidants and degradation of organic contaminants: A QSAR modeling study

Oxidation is an attractive treatment method to effectively remove organic contaminants in water. In this study, degradation of 30 organic compounds in different oxidation systems was evaluated, including oxygen (O₂), hydrogen peroxide (H₂O₂), ozone (O₃) and hydroxyl radical (HO). First, a quantitative structure-activity relationship (QSAR) model for oxidation-reduction potentials (ORPs) of organics was developed and exhibited a good performance to predict ORP values of organics with evaluation indices of squared correlation coefficient (R²) = 0.866, internal validation (q²) = 0.811 and external validation (Q_ext²) = 0.669. Four quantum parameters, including f(+)_n, f(-)_n, E_HOMO and E_B3LYP dominate the ORP values. Subsequently, a relationship between reaction rates (k) and the difference of ORP for oxidants and organics (ΔE_oxi-org) was established, however, which was limited (R²= 0.697). Therefore, two new predictors (slopes and intercepts) are proposed based on the linear relationships between k values and ORPs of oxidants. These new predictors can be applied to estimate the reaction rates and minimum oxidation potential for organic compounds. Afterwards, to express the two predictors, QSAR models were established. The two optimal QSAR models fitted very well with experimental values and were demonstrated to be stable and accurate based on R² (0.982 and 0.965), q² (0.950 and 0.950) and Q_ext² (0.985 and 0.989). BO_x, q(H)⁺ and q(C)_x were main factors influencing the slopes and intercepts. This study developed methods to predict ORPs of organics and established two new predictors to estimate the reaction rates undergoing different oxidation processes, offering new insights into the oxidant selection.

Fabrication of iron-dipicolinamide catalyst with Fe-N bonds for enhancing non-radical reactive species under alkaline Fenton process

Iron dipicolinamide (Fedpa), as an efficient Fenton-like catalyst, was fabricated to excite hydrogen peroxide (H₂O₂) for the removal of 2,4-dichlorophenol (2,4-DCP). The unique structures and the electronic properties of Fedpa were contributed to its excellent catalytic performance in alkaline Fenton process. Fe was chelated with dpa by four Fe-N bonds leaved two labile sites, which reduced the oxidation potential of dpa[Fe^III/Fe^II], dpa[Fe^V/Fe^III] or dpa[Fe^IV/Fe^II] to 0.316 V and 1.189 V respectively, and made it easily be bound with H₂O₂ to initiate the reaction. The results showed that 99.5% removal rate of 2,4-DCP (0.58 mM) was achieved by using 0.027 g/L Fedpa and 5.8 mM H₂O₂ in 60 min at pH 9.9. The coordination between Fe and dpa enhanced the catalytic efficiency of Fe^II. The active species generated in Fedpa/H₂O₂ system contained the iron-oxo species (dpaFe^V = O or dpa^IV = O), O₂^- and HO. The iron-oxo species was the main non-radical reactive species for the degradation of 2,4-DCP and some degradation intermediates were detected by GC-QTOF. Furthermore, the influence of factors, such as Fedpa loading, solution pH, temperature and anions (F^-, Cl^-, SO₄^2-, NO₃^- and PO₄^3-) on the catalytic performance of Fedpa were also discussed. This process of complexation between Fe and dpa combined with a green oxidant H₂O₂ presents a new insight for the use of Fenton-like system in the degradation of refractory organics.

Synergistic effects of combining ozonation, ceramic membrane filtration and biologically active carbon filtration for wastewater reclamation

In this study, we proposed to apply an integrated process which is comprised of in situ ozonation, ceramic membrane filtration (CMF) and biologically active carbon (BAC) filtration to wastewater reclamation for indirect potable reuse purpose. A pilot-scale (20 m³/d) experiment had been run for ten months to validate the prospect of the process in terms of treatment performance and operational stability. Results showed that the in situ O₃ + CMF + BAC process performed well in pollutant removal, with chemical oxygen demand, ammonia, nitrate nitrogen, total phosphorus and turbidity levels in the treated water being 5.1 ± 0.9, 0.05 ± 0.01, 10.5 ± 0.8, <0.06 mg/L, and <0.10 NTU, respectively. Most detected trace organic compounds were degraded by>96%. This study demonstrated that synergistic effects existed in the in situ O₃ + CMF + BAC process. Compared to pre-ozonation, in situ ozonation in the membrane tank was more effective in controlling membrane fouling (maintaining operational stability) and in degrading organic pollutants, which could be attributed to the higher residual ozone concentration in the tank. Because of the removal of particulate matter by CMF, water head loss of the BAC filter increased slowly and prolonged the backwashing interval to 30 days. BAC filtration was also effective in removing ammonia and N-nitrosodimethylamine from the ozonated water.

The Generation of the Oxidant Agent of a Mononuclear Nonheme Fe(II) Biomimetic Complex by Oxidative Decarboxylation. A DFT Investigation

The oxidative decarboxylation of the iron(II) α-hydroxy acid (mandelic acid) complex model, biomimetic of Rieske dioxygenase, has been investigated at the density functional level. The explored mechanism sheds light on the role of the α-hydroxyl group on the dioxygen activation. The potential energy surfaces have been explored in different electronic spin states. The rate-determining step of the process is the proton transfer. The oxidative decarboxylation preferentially takes place on the quintet state.

FerrateVI oxidation of polycyclic aromatic compounds (PAHs and polar PACs) on DNAPL-spiked sand: degradation efficiency and oxygenated by-product formation compared to conventional oxidants

In situ chemical oxidations are known to remediate PAH contaminations in groundwater and soils. In this study, batch-scale oxidations aim to compare the PAC (polycyclic aromatic compound) degradation of three oxidation processes traditionally applied for soil treatment: permanganate, heat-activated persulfate (60 °C) and Fenton-like activated by magnetite, to results obtained with ferrates (Fe^VI). Widely studied for water treatments, ferrates are efficient on a wide range of pollutants with the advantage of producing nontoxic ferric sludge after reaction. However, fewer works focus on their action on soil, especially on semi-industrial grade ferrates (compatible with field application). Oxidations were carried out on sand spiked with dense non-aqueous phase liquid (DNAPL) sampled in the groundwater of a former coking plant. Conventional 16 US-EPA PAHs and polar PACs were monitored, especially potential oxygenated by-products that can be more harmful than parent-PAHs. After seven reaction days, only the Fenton-like showed limited degradation. Highest efficiencies were obtained for heat-activated persulfate with no O-PAC ketones formed. Permanganate gave important degradation, but ketones were generated in large amount. The tested ferrates not only gave slightly lower yields due to their auto-decomposition but also induced O-PAC ketone production, suggesting a reactional pathway dominated by oxidoreductive electron transfer, rather than a radical one.

Assessing the performance of electrochemical oxidation using DSA® and BDD anodes in the presence of UVC light

Significance of surface and ground water contamination by synthetic organic compounds has been pointed out in a very high number of papers worldwide, as well as the need of application of treatment technologies capable to assure their complete removal. Among these processes, the electrochemical advanced oxidation is an interesting option, especially when irradiated with UVC light (photo-electrochemical, P-EC) to promote homolysis of electrogenerated oxidants. In this work, the herbicide glyphosate (GLP) was used as model compound and it was electrochemically treated under UVC irradiation in the presence of NaCl and using a DSA® and BDD anodes. Total organic carbon concentration was measured throughout the electrolysis, as well as the concentration of short chain carboxylic acids and inorganic ions (NO3-, PO43-,ClO-, ClO3- and ClO4-). The synergism of the P-EC was more pronounced when using a DSA® electrode, which led to complete GLP mineralization in 1 h (0.52 A h L-1), as also confirmed by the stoichiometric formation of NO3- and PO43- ions, with an energy consumption as low as 1.25 kW h g-1. Unexpectedly, the concentration evolution of oxyhalides for the P-EC process using both anodes, especially for DSA® at 10 mA cm-2, showed the production of ClO3-, whereas detection of ClO4- species was only found when using BDD at 100 mA cm-2 for the electrochemical process. Finally, small amounts of carboxylic acids were detected, including dichloroacetic acid, especially when using a BDD electrode.

Atmospheric oxidation of HFE-7300 [n-C2F5CF(OCH3)CF(CF3)2] initiated by •OH/Cl oxidants and subsequent degradation of its product radical: a DFT approach

To understand the atmospheric chemistry of hydrofluoroethers, we have studied the oxidation of a highly fluorinated compound n-C₂F₅CF(OCH₃)CF(CF₃)₂ (HFE-7300) by OH/Cl oxidants. Here, we have employed M06-2X functional along with a 6-31 + G(d,p) basis set to obtain the optimized structures, various forms of energies, and different modes of frequencies for all species. We have characterized energies of all species on the potential energy surface, and it indicates that H-abstraction from n-C₂F₅CF(OCH₃)CF(CF₃)₂ by Cl atom is kinetically more dominant than the H-abstraction reaction initiated by OH radical. In contrast, the calculated energy change (Δ_rH°₂₉₈ and Δ_rG°₂₉₈) results govern that OH-initiated H-abstraction reaction is highly exothermic and spontaneous compared to the Cl-initiated H-abstraction reaction. Rate constants are estimated using transition state theory as well as canonical variation transition state theory at the temperature range 200-1000 K and 1 atm pressure. The calculated rate constants of the H-abstraction channels are found to be in good agreement with the reported experimental rate constant at 298 K. Moreover, we have estimated the atmospheric lifetimes of HFE-7300 for the reaction with OH radical and Cl atom and are found to be 1.75 and 153.93 years, respectively. Additionally, the global warming potentials for HFE-7300 molecule are also estimated for 20-, 100-, and 500-year time horizons. Further, subsequent aerial oxidation of product radical (n-C₂F₅CF(OCH₂)CF(CF₃)₂) in the presence of NO radical is performed, and it produced alkoxy radical via formation of peroxy radical. This alkoxy radical undergoes unimolecular decompositions via two different ways and formed n-C₂F₅CF(OCHO)CF(CF₃)₂ and n-C₂F₅CF(OH) CF(CF₃)₂ products.

Lewis acids promoted organic pollutants degradation in aqueous solution with peroxymonosulfate and MnO2: New insights into the activation mechanism

Nonredox metal ions have been widely recognized to be important in a wide range of biological and chemical oxidations as Lewis acids (LA). However, the role of LA in peroxymonosulfate (PMS) activation for wastewater treatment has not been considered until now. This study shows that oxidizing power of PMS can be promoted after binding nonredox metal ions such as Ca²⁺ as LA, leading to the easier reduction of the oxidant to radicals and substantial enhancement of dye degradation by employing manganese oxides OMS-2 as model catalysts. Increased with Lewis acidity of the metal ion, the rate of PMS decomposition enhanced linearly, while the dye degradation rate first increased and then declined due to the formation of a larger amount of dioxygen. The interactions between Ca²⁺ and PMS were further investigated by Raman, cyclic voltammetry and XPS; and the detailed mechanism of PMS activation was proposed. The performance of Ca²⁺+OMS-2/PMS system under different conditions was also studied. The findings indicate the importance of LA in PMS activation reaction and their role must be considered in other transition metal oxides/PMS systems. It will be also helpful to design new and highly active catalysts for the reactions.

Soil infiltration capacity of chemical oxidants used for risk reduction of soil contamination

Chemical oxidation has been applied to remove soil contaminants and thereby reduce human and ecological risks from contaminated sites. However, few studies have been conducted on the natural infiltration of oxidant solutions into unsaturated soil. Moreover, the infiltration capacity of oxidant solutions at various concentrations in unsaturated soil has not yet been studied. This study investigated the natural infiltration tendency of oxidant solutions like hydrogen peroxide (H₂O₂), potassium permanganate (KMnO₄), and sodium persulfate (Na₂S₂O₈), in sand and sandy loam. Cumulative infiltration was recorded from a soil column equipped with a Mariotte reservoir. The infiltration rate, sorptivity, and unsaturated hydraulic conductivity were obtained from the cumulative infiltration results. Na₂S₂O₈ showed the highest infiltration rate in both sand and sandy loam, and the infiltration of Na₂S₂O₈ increased as the concentration was increased from 0.05 to 1%. However, the infiltration of KMnO₄ and H₂O₂ solutions was governed more by chemical reaction behavior than by liquid physical properties or soil hydraulic properties. The production of oxides and gas due to reaction induced clogging in flow paths, resulting in less infiltration. Infiltration of H₂O₂ at concentrations greater than 0.5% was not observed in sand or sandy loam due to gas formation and swelling.

Modeling chlorine-produced oxidant demand and dilution in chlorinated combined sewer overflow discharges

Combined sewer overflow (CSO) water introduces pathogens to receiving waters. To control pathogenic releases, chlorine may be added to disinfect CSO water. The added chlorine may react with water constituents to form oxidative species known as chlorine-produced oxidants (CPO). CPO are the sum of free and combined oxidative species that form upon adding free chlorine-bearing compounds (e.g. gaseous chlorine or hypochlorite) to water. CPO discharge is often regulated by governing agencies. Current methods to model CPO behavior do not account for CPO decay and dilution simultaneously in receiving water. This study creates a novel model for CPO demand and dilution in receiving water from chlorinated effluent in order to determine site-specific practices for implementation of a CSO water disinfection regime. To do this, representative receiving water was collected and dosed with 1, 2, and 4 mg/L chlorine. The residual chlorine was measured at intervals up to 30 min after dosing. The immediate and subsequent chlorine demand was calculated, with the subsequent demand modeled by simultaneous application of dilution and decay using pseudo-first-order decay kinetics. A comparison of model calculations indicates that application of dilution before decay underestimates CPO demand, while application of decay before dilution overestimates CPO demand.

Acid Orange 7 treatment and fate by electro-peroxone process using novel electrode arrangement

Electro-peroxone is a novel advanced oxidation process that surpasses ozonation or peroxone because of its advantages. In this technology, combining ozone and hydrogen peroxide generated electrochemically leads to the production of hydroxyl radicals, which are the strongest oxidizing agents. In this study, a cylindrical reactor with a continuous circular flow using novel arrangements of electrodes was used to examine the effects of variant parameters on dye removal efficiency. Acid Orange 7 (C₁₆H₁₁N₂NaO₄S) served as an indicator pollutant. Based on overall energy consumption and energy consumption per dye removed weight, electro-peroxone not only has proper efficiency at high dye concentrations, it also has the least energy consumption per dye removed weight; 53 KWh kg^-1 is achieved for 500 mg L^-1 initial dye concentration at 99% removal efficiency after 40 min. The results show that at the optimum condition of [Dye] = 500 mg L^-1, pH = 7.7, applied current = 0.5 A, O₃ rate = 1 L min^-1, and [Na₂SO₄] = 0.1 M, dye is removed completely after 90 min and COD and TOC removal is 99% and 90%, respectively. LC-MS results also showed that AO7 initially was converted to more toxic compounds than AO7 like benzoic acid but finally linear acidic intermediate with less toxicity such as fumaric acid was formed.

Comparative study of persulfate oxidants promoted photocatalytic fuel cell performance: Simultaneous dye removal and electricity generation

Introducing peroxymonosulfate (PMS) and peroxydisulfate (PDS) into the photocatalytic fuel cell (PFC) system were investigated by comparing the Reactive Brilliant Blue (KN-R) degradation and synchronous electricity production. The two persulfates (PS) themselves are strong oxidant, and could be activated and as electron sacrificial agent in the PFCs, facilitating the photoelectrocatalysis and expanding redox to the entire cell space. Hence, the two established PFC/PS systems manifested prominent cell performances, enhancing the KN-R decomposition and electric power production relative to the virgin PFC. Thereinto, the KN-R removal rate of PFC/PMS was faster than that of PFC/PDS, but an opposite trend appeared in the electricity generation. Besides, the cell performances of the two cooperative systems were evaluated at different operation conditions, including PS dosage, solution pH, and irradiation strength. Moreover, the dye elimination principle was explored by radicals scavenging experiment, and the consequence revealed that hydroxyl radical (HO^•), sulfate radical (SO₄^•-) and singlet oxygen were chief active species in the PFC/PMS, and HO^•, SO₄^•- and superoxide anion played the key roles in the PFC/PDS. Furthermore, the calculated economic indicator demonstrated that the economy of the two synergistic processes were greater than that of UV/PS and solo PFC, and the PFC/PDS was more cost-effective than PFC/PMS.

Differential oxidation processes of peroxiredoxin 2 dependent on the reaction with several peroxides in human red blood cells

Peroxiredoxins (Prxs) detoxify hydrogen peroxide (H₂O₂), peroxynitrite, and various organic hydroperoxides. However, the differential oxidative status of Prxs reacted with each peroxide remains unclear. In the present study, we focused on the oxidative alteration of Prxs and demonstrated that, in human red blood cells (RBCs), peroxiredoxin 2 (Prx2) is readily reactive with H₂O₂, forming disulfide dimers, but was not easily hyperoxidized. In contrast, Prx2 was highly sensitive to the relatively hydrophobic oxidants, such as tert-butyl hydroperoxide (t-BHP) and cumene hydroperoxide. These peroxides hyperoxidized Prx2 into oxidatively damaged forms in RBCs. The t-BHP treatment formed hyperoxidized Prx2 in a dose-dependent manner. When organic hydroperoxide-treated RBC lysates were subjected to reverse-phase high performance liquid chromatography, two peaks derived from hyperoxidized Prx2 appeared along with the decrease of that corresponding to native Prx2. Liquid chromatography-tandem mass spectrometry analysis clearly showed that hyperoxidation to sulfonic acid (-SO₃H) at Cys-51 residue was more advanced in a newfound hyperoxidized Prx2 compared to another hydrophobic hyperoxidized form previously identified. These results indicate that irreversible hyperoxidation of the Prx2 monomer in RBCs was easily caused by organic hydroperoxide but not H₂O₂. Thus, it is important to detect the hyperoxidation of Prx2 into sulfinic or sulfonic acid derivates of Cys-51 because hyperoxidized Prx2 is a potential marker of oxidative injury caused by organic hydroperoxides in human RBCs.

Enteromorpha prolifera-derived Fe3C/C composite as advanced catalyst for hydroxyl radical generation and efficient removal for organic dye and antibiotic

Enteromorpha prolifera-derived Fe₃C/C composite has been fabricated through a facile one-step calcination method. As an advanced Fenton-like catalyst, the obtained Fe₃C/C composite displayed high catalytic reactivity to generate hydroxyl radicals. It is worth to note that the removal rate of methylene blue (MB) could effectively reach 100% in a wide pH range (pH = 2˜12) and the maximum degradation capacity of the composite is 660 mg/g. The stability and reusability of Fe₃C/C composite catalyst have also been tested, which could remain the removal rate at 100% after 6 consecutive runs. To illustrate the practical application possibility, the Fe₃C/C composite catalyst was used for degradation of papermaking and dyeing waste water, which could reduce the COD (chemical oxygen demand) value to less than 50. Additionally, the antibiotic norfloxacin (NOR) could also be catalytically removed by the Fe₃C/C composite and the possible removal pathway has also been proposed. The excellent removal performance of Fe₃C/C composite for MB and NOR may be attributed to the synergistic effect between porous carbon adsorption and Fe₃C catalysis. This study not only provides novel insights into recycling of waste biomass, but also paves a new way for the application of Fe₃C/C in dyes and antibiotics waste water treatment areas.

Efficient atrazine degradation catalyzed by manganese porphyrins: Determination of atrazine degradation products and their toxicity evaluation by human blood cells test models

Atrazine (ATZ) is an herbicide that has been considered an environmental pollutant worldwide. ATZ contaminates groundwaters and can persist in soils for up to a year causing several environmental and health problems. This study aimed to investigate ATZ degradation catalyzed by manganese porphyrins as biomimetic cytochrome P450 models. We used PhIO, PhI(OAc)₂, H₂O₂, t-BuOOH, m-CPBA, or Oxone^® as oxidant under mild conditions and evaluated a range of manganese porphyrins as catalyst. Concerning oxidant, iodosylbenzene provided the best result-ATZ degradation catalyzed by one of the studied manganese porphyrins in acetonitrile was as high as 47%. We studied the same catalyst/oxidant systems in natural water from a Brazilian river as solvent and obtained up to 100% ATZ degradation when iodobenzene diacetate was the oxidant, regardless of the manganese porphyrin. Besides the already known ATZ degradation products, we also identified unexpected degradation compounds (ring-opening products). Toxicity tests showed that the latter products were capable of proliferate blood cells because they did not show toxicity under the evaluated conditions.

Kinetics of Flavoenzyme-Catalyzed Reduction of Tirapazamine Derivatives: Implications for Their Prooxidant Cytotoxicity

Derivatives of tirapazamine and other heteroaromatic N-oxides (ArN→O) exhibit promising antibacterial, antiprotozoal, and tumoricidal activities. Their action is typically attributed to bioreductive activation and free radical generation. In this work, we aimed to clarify the mechanism(s) of aerobic mammalian cell cytotoxicity of ArN→O performing the parallel studies of their reactions with NADPH:cytochrome P-450 reductase (P-450R), adrenodoxin reductase/adrenodoxin (ADR/ADX), and NAD(P)H:quinone oxidoreductase (NQO1); we found that in P-450R and ADR/ADX-catalyzed single-electron reduction, the reactivity of ArN→O (n = 9) increased with their single-electron reduction midpoint potential (E¹₇), and correlated with the reactivity of quinones. NQO1 reduced ArN→O at low rates with concomitant superoxide production. The cytotoxicity of ArN→O in murine hepatoma MH22a and human colon adenocarcinoma HCT-116 cells increased with their E¹₇, being systematically higher than that of quinones. The cytotoxicity of both groups of compounds was prooxidant. Inhibitor of NQO1, dicoumarol, and inhibitors of cytochromes P-450 α-naphthoflavone, isoniazid and miconazole statistically significantly (p < 0.02) decreased the toxicity of ArN→O, and potentiated the cytotoxicity of quinones. One may conclude that in spite of similar enzymatic redox cycling rates, the cytotoxicity of ArN→O is higher than that of quinones. This is partly attributed to ArN→O activation by NQO1 and cytochromes P-450. A possible additional factor in the aerobic cytotoxicity of ArN→O is their reductive activation in oxygen-poor cell compartments, leading to the formation of DNA-damaging species similar to those forming under hypoxia.

Protective Role of Melatonin in Streptozotocin Induced Pancreatic Damages in Diabetic Wistar Rat

BACKGROUND AND OBJECTIVE

Hyperglycemia is a representative hallmark and risk factor for diabetes and is closely linked to diabetes associated complications. The aim of the present study was to evaluate the therapeutic potential of exogenous melatonin against the streptozotocin induced pancreatic damages in rats.

MATERIALS AND METHODS

Streptozotocin was injected for consecutive 6 days. Diabetes was confirmed by blood glucose measurement after 72 h and on 7th day after injection. Animals having blood glucose level above 250 mg dL-1 were considered as diabetic and were administered exogenous melatonin for 4 weeks. Animals were euthanized after last dose, pancreas were dissected out, weighed and fixed in Bouin's fixative for histology and further tissues were kept at -20°C for biochemistry.

RESULTS

Diabetic rats displayed significant increase in lipid peroxidation, but pancreatic weight index, antioxidant system (GSH, SOD and CAT) showed decrease. Melatonin treatment to diabetic rats restored the alteration in physiological and biochemical markers. Results were supported by the histopathological observations, STZ treated pancreas showed damage in islets of langerhans, while as melatonin treated diabetic rats recovered the cellular architecture which inturn normalize the function of the pancreas.

CONCLUSION

Therefore, melatonin might be considered as a molecule to protect the pancreatic damages.

Biomimetic Non-Heme Iron-Catalyzed Epoxidation of Challenging Terminal Alkenes Using Aqueous H2O2 as an Environmentally Friendly Oxidant

Catalysis mediated by iron complexes is emerging as an eco-friendly and inexpensive option in comparison to traditional metal catalysis. The epoxidation of alkenes constitutes an attractive application of iron(III) catalysis, in which terminal olefins are challenging substrates. Herein, we describe our study on the design of biomimetic non-heme ligands for the in situ generation of iron(III) complexes and their evaluation as potential catalysts in epoxidation of terminal olefins. Since it is well-known that active sites of oxidases might involve imidazole fragment of histidine, various simple imidazole derivatives (seven compounds) were initially evaluated in order to find the best reaction conditions and to develop, subsequently, more elaborated amino acid-derived peptide-like chiral ligands (10 derivatives) for enantioselective epoxidations.

Microwave-Assisted Digestion Procedures Using Diluted Oxidant Mixture for Elemental Analysis of Crustaceans by MIP OES

The aim of this study was to evaluate three digestion procedures using a diluted oxidant mixture of nitric acid, hydrogen peroxide, and water for determination of Cu, Fe, K, Mg, Mn, and Zn in shrimp and crab samples from Northern Brazil by microwave-induced plasma optical emission spectrometry. The efficiency of the digestion procedure was evaluated by comparing the residual carbon content, residual acidity, and elemental concentrations obtained in the samples. Digestion procedure 2 (4 mL HNO₃ + 4 mL H₂O₂ + 4 mL H₂O) was chosen due the adequate residual carbon content (5.85%) and low residual acidity (2.94 mol L^-1). The recoveries obtained using the certified reference material (DORM-4) varied from 90 to 105%. High contents of K and Mg were found in the studied crustaceans. Also, it can give an excellent contribution to the recommended daily intake of Cu and Zn, indicating that these foods can be considered a good source of these minerals for the human diet.

Semi-automatic combustion of environmental and biological samples on Oxidizer M307 and equivalents: New solutions for background reduction

The aim is to introduce and characterize a new experimental demonstrative model contributing to the increase of measurement accuracy, in terms of minimum detectable activity (MDA) and background reduction, for the analysis of samples having low concentrations in tritium and radiocarbon on Quantulus 1220. The clue is related to the qualitative and quantitative differences between tritium and carbon-14 inventories of the pulp used to manufacture the cups involved in noncatalytic combustion of samples by flame oxidation method. The quality of the experimental results depends on the temporal origin of the wood from which the pulp/cellulose was extracted/purified, the specific inventory contributing to the threshold level of the MDA for the beta-emitting radionuclide to be investigated. Finally, the aim is to create and to use such a 100% old cellulose combustion cups for determining low concentrations of these radionuclides. It may be obtained by an adapted technology following the literature data and may be recommended for routine analyses of environmental samples coming from areas with no nuclear or minor nuclear influences, and also for low-level biological samples. This first attempt resulted in improvement of measurement performances up to 400% for carbon-14 and by approximately 50% for tritium.

Effects of oxidant and catalyst on the transformation products of rocket fuel 1,1-dimethylhydrazine in water and soil

Existing methods for cleanup of wastewaters and soils polluted with the extremely toxic rocket fuel unsymmetrical dimethylhydrazine (UDMH) are mainly based on the treatment with various oxidative reagents. Until now, the assessment of their effectiveness was based on the residual content of UDMH and did not take into account the possibility of the formation of a large number of potentially dangerous nitrogen-containing transformation products (TPs). In this study, using the recently developed approach based on high-resolution Orbitrap mass spectrometry, the comprehensive characterization of UDMH TPs formed by the action of air oxygen and different oxidants (Fenton's reagent, KMnO₄, HOCl, H₂O₂ in the presence of Cu²⁺ and [Fe (EDTA)]^- catalysts) typically used to detoxify spill sites was performed. The range of the identified molecular formulas of TPs comprised 303 compounds of various classes. Among them, there is a number of major products not previously described in the literature. It was established that none of the investigated oxidative reagents ensures complete conversion of rocket fuel to safe compounds. The hydrogen peroxide based reagents, particularly H₂O₂ + Na [Fe (EDTA)] system currently used in Kazakhstan, give the greatest number of TPs, for many of which a toxicity was not characterized so far. The majority of the compounds found in model solutions was detected in extracts of soil from the crash site of the Proton carrier rocket, which was subjected to the on-site reagent treatment. During successive treatments, along with the decrease in the number of detectable UDMH TPs, their ratios change in favor of amines.

Sonocatalytic degradation of tetracycline antibiotic using zinc oxide nanostructures loaded on nano-cellulose from waste straw as nanosonocatalyst

The aim of the present investigation was the combination of ZnO nanostructures with nano-cellulose (NC) for the efficient degradation of tetracycline (TC) antibiotic under ultrasonic irradiation. The removal efficiency of 12.8% was obtained by the sole use of ultrasound (US), while the removal efficiency increased up to 70% by the US/ZnO treatment process. Due to the integration of ZnO nanostructures with NC, the removal efficiency of 87.6% was obtained within 45 min. The removal efficiency substantially decreased in the presence of tert-butyl alcohol (more than 25% reduction), indicating that ^radOH-mediation oxidation is responsible for the degradation of TC molecules. Peroxymonosulfate (PMS) led to the most enhancing effect on the removal of TC among percarbonate, persulfate and periodate ions. The addition of PMS caused the degradation efficiency of 96.4% within the short contact time of 15 min. The bio-toxicity examination on the basis of inhibition test conducted on activated sludge revealed diminishing the oxygen consumption inhibition percent [I_OUR (%)] from 33.6 to 22.1% during the US/ZnO/NC process. Consequently, the utilization of the US/ZnO/NC process can convert TC molecules to less toxic compounds. However, longer reaction time is required for complete conversion into non-toxic substances.

Effect of various chemical oxidation reagents on soil indigenous microbial diversity in remediation of soil contaminated by PAHs

Chemical oxidation is a promising pretreatment step coupled with bioremediation for removal of polycyclic aromatic hydrocarbons (PAHs). The effectiveness of Fenton, modified Fenton, potassium permanganate and activated persulfate oxidation treatments on the real contaminated soils collected from a coal gas plant (263.6 ± 73.3 mg kg^-1 of the Σ16 PAHs) and a coking plant (385.2 ± 39.6 mg kg^-1 of the Σ16 PAHs) were evaluated. Microbial analyses showed only a slight impact on indigenous microbial diversity by Fenton treatment, but showed the inhibition of microbial diversity and delayed population recovery by potassium permanganate reagent. After potassium permanganate treatment, the microorganism mainly existed in the soil was Pseudomonas or Pseudomonadaceae. The results showed that total organic carbon (TOC) content in soil was significantly increased by adding modified Fenton reagent (1.4%-2.3%), while decreased by adding potassium permanganate (0.2%-1%), owing to the nonspecific and different oxidative properties of chemical oxidant. The results also demonstrated that the removal efficiency of total PAHs was ordered: permanganate (90.0%-92.4%) > activated persulfate (81.5%-86.54%) > modified Fenton (81.5%-85.4%) > Fenton (54.1%-60.0%). Furthermore, the PAHs removal efficiency was slightly increased on the 7th day after Fenton and modified Fenton treatments, about 14.6%, and 14.4% respectively, and the PAHs removal efficiency only enhanced 4.1% and 1.3% respectively from 1st to 15th day after potassium permanganate and activated persulfate treatments. The oxidants greatly affect the growth of soil indigenous microbes, which cause further influence for PAHs degradation by bioremediation.

Photo-oxidative degradation of doxorubicin with siloxane MOFs by exposure to daylight

Doxorubicin (DOX) is a chemotherapeutic agent from anthracycline class, which acts unselectively on all cells; thus, it may have genotoxic and/or mutagenic effects and cause serious environmental problems. Herein, the decomposition of a diluted solution of DOX hydrochloride for injection has been investigated under photo-oxidative conditions, in ambient light and without pH modification, using hydrogen peroxide as oxidizing agent and hydrophobic siloxane-based metal-organic frameworks (MOFs) as heterogeneous catalysts. The kinetics of the photodegradation process was followed by UV-Vis spectroscopy and by ESI-MS. According to UV-Vis data, two pseudo-first-order kinetic steps describe the process, with rate constants in the order of 10^-3-10^-2 min^-1 for the rate-determining one. ESI-MS provided more accurate information, with a rate constant of 2.6 · 10^-2 min^-1 calculated from the variation of DOX ion abundance. Complete decomposition of DOX was achieved after 120 min in the shade and after only 20 min by exposure to sunlight. The analysis of the residual waters by mass spectrometry and 1D and 2D NMR spectroscopy showed complete disappearance of DOX in all cases, excluded any anthracycline species, which are destroyed in the tested conditions, and proved formation of an un-harmful compound-glycerol, while no trace of metal was detected by XRF. Preliminary data also showed decomposition of oxytetracycline in similar conditions. By this study, we bring into attention a less-addressed pollution issue and we propose a mild and effective method for the removal of drug emerging pollutants.

Quick vaporization of sprayed sodium hypochlorite (NaClO(aq)) for simultaneous removal of nitrogen oxides (NOx), sulfur dioxide (SO2), and mercury (Hg0)

Sodium hypochlorite (NaClO) has been widely used as a chemical additive for enhancing nitrogen oxide (NO_x; NO + NO₂), sulfur dioxide (SO₂), and mercury (Hg⁰) removals in a wet scrubber. However, they are each uniquely dependent on NaClO_(aq) pH, hence making the simultaneous control difficult. In order to overcome this weakness, we sprayed low liquid-to-gas (L/G) ratio (0.1 L/Nm³) of NaClO_(aq) to vaporize quickly at 165 °C. Results have shown that the maximized NO_x, SO₂, and Hg⁰ removals can be achieved at the pH range between 4.0 and 6.0. When NO_x and Hg⁰ coexist with SO₂, in addition, their removals are significantly enhanced by reactions with solid and gaseous by-products such as NaClO_(s), NaClO_2(s), OClO, ClO, and Cl species, originated from the reaction between SO₂ and NaClO_(aq). We have also demonstrated the feasibility of this approach in the real flue gases of a combustion plant and observed 50%, 80%, and 60% of NO_x, SO₂, and Hg⁰ removals, respectively. These findings led us to conclude that the spray of NaClO_(aq) at a relatively high temperature at which the sprayed solution can vaporize quickly makes the simultaneous control of NO_x, SO₂, and Hg⁰ possible. Implications: The simple spray of NaClO_(aq) at temperatures above 165 °C can cause the simultaneous removal of gaseous NO_x, SO₂, and Hg⁰ by its quick vaporization. Their maximized removals are achieved at the pH range between 4.0 and 6.0. NO_x and Hg⁰ removals are also enhanced by gaseous and solid intermediate products generated from the reaction of SO₂ with NaClO_(aq). The feasibility of this approach has been demonstrated in the real flue gases of a combustion plant.

Evaluation of transformation products from chemical oxidation of micropollutants in wastewater by photoassisted generation of sulfate radicals

In this research, the degradation of seven different micropollutants (MPs) and the formation of their transformation products (TPs) have been assessed during the application of different advanced oxidation processes: photolytic and photocatalytic activation of peroxymonosulfate (PMS) and persulfate (PS). The results were compared with those obtained from the photolytic experiments using hydrogen peroxide (H₂O₂) as oxidant. A significant abatement of almost all MPs was achieved, even with very low UV-C contact time (9 and 28 s). The degradation of atenolol (ATN) and caffeine (CFN) ranged from 84 to 100% with a dose of 0.5 mM of any oxidant. The efficiencies for bisphenol-A (BPA), carbamazepine (CBZ), diclofenac (DCF), ibuprofen (IBP), and sulfamethoxazole (SMX) varied depending on the oxidation system and operating conditions (oxidant dose and UV-C contact time), leading to the photolysis of PMS to higher efficiencies than PS and H₂O₂. In all cases, the abatement of MPs ranged from 63 to 83%, even with the lowest PMS dosage. Moreover, the addition of Fe(II) as a catalyst enhanced the removal efficiency, reaching almost total removal, especially over CBZ, DCF, and IBP. The Dissolved Organic Carbon (DOC) removal ranged between 44 and 62%, suggesting the transformation of MPs in intermediate compounds. The identification of transformation products was carried out for each micropollutant and each oxidation treatment, being observed some transformation products specific of oxidation by sulfate radicals. For example, m/z 165.0432 only appeared after PMS/Fe(II)/UV-C on the degradation of BFA, m/z 251.082 appeared after photolytic activation of PMS and PS on CBZ removal, and m/z 128.0452 was observed after any sulfate radical oxidation treatment, but not after photolysis of H₂O₂.

Sorbus domestica Leaf Extracts and Their Activity Markers: Antioxidant Potential and Synergy Effects in Scavenging Assays of Multiple Oxidants

Sorbus domestica leaves are a traditionally used herbal medicine recommended for the treatment of oxidative stress-related diseases. Dry leaf extracts (standardized by LC-MS/MS and LC-PDA) and nine model activity markers (polyphenols), were tested in scavenging assays towards six in vivo-relevant oxidants (O2•-, OH•, NO•, H2O2, ONOO-, HClO). Ascorbic acid (AA) and Trolox (TX) were used as positive standards. The most active extracts were the diethyl ether and ethyl acetate fractions with activities in the range of 3.61-20.03 µmol AA equivalents/mg, depending on the assay. Among the model compounds, flavonoids were especially effective in OH• scavenging, while flavan-3-ols were superior in O2•- quenching. The most active constituents were quercetin, (-)-epicatechin, procyanidins B2 and C1 (3.94-24.16 µmol AA/mg), but considering their content in the extracts, isoquercitrin, (-)-epicatechin and chlorogenic acid were indicated as having the greatest influence on extract activity. The analysis of the synergistic effects between those three compounds in an O2•- scavenging assay demonstrated that the combination of chlorogenic acid and isoquercitrin exerts the greatest influence. The results indicate that the extracts possess a strong and broad spectrum of antioxidant capacity and that their complex composition plays a key role, with various constituents acting complementarily and synergistically.

Fenton-like and potassium permanganate oxidations of PAH-contaminated soils: Impact of oxidant doses on PAH and polar PAC (polycyclic aromatic compound) behavior

Potassium permanganate and Fenton-like oxidations were applied on two PAH-contaminated soils collected on former coking plant and gas plant sites. The impact of oxidant dose on the polycyclic aromatic compound (PAC) evolution, including 16 US-EPA PAHs, 11 oxygenated- and 4 nitrogen heterocyclic-PACs (O- and N-PACs) was studied for both treatments. The content of extractable organic matter and PACs was determined prior and after oxidation. Overall, permanganate treatment was more efficient than Fenton-like to decrease the PAH content, this latter being limited by the contamination availability. However, permanganate treatment resulted in incomplete PAH degradation, leading to the formation of O-PACs, that was limited with the application of higher dose. It underlines the importance of the dose and the oxidant type in the selection of oxidation parameters for remediation purpose, as improper use of oxidant can lead to the accumulation of oxidation by-products that could be as toxic as the parent compounds.

Degradation of sulfanilamide by Fenton-like reaction and optimization using response surface methodology

Excess sulfonamides are discharged into the environmental system due to the abuse of antibiotics, which threatens the ecological environment and human health. In this study, the ferric and ferrous as well as calcium peroxide (CP), sodium percarbonate (SPC) and sodium persulfate (SPS) have been used to build Fenton-like system for the sulfanilamide (SA) removal. Compared with other Fenton-like system, the Fe³⁺/CP system exhibited better degradation capacity and 94.65% SA was removed with 3.0 mM CP and 3.0 mM Fe³⁺. A response surface and corresponding quadratic regression equation were obtained by using a three-level Box-Behnken factorial design with the initial pH value and the dosage of Fe³⁺ and CP as the model parameters. Depended on the result of the response surface, the optimum conditions of the removal of SA in Fe³⁺/CP system could be obtained: [Fe³⁺] = 2.96 mM, [CaO₂] = 2.33 mM and [pH] = 6.45. Besides that, the influences of Na⁺, Mg²⁺, Cl^-, HCO₃^-, NO₃^- and HA on SA removal were also investigated under the optimum condition. The results revealed that the high concentration of HCO₃^- was able to inhibit degradation of SA while other ions and HA have little effect on SA degradation. These results provided a novel strategy to evaluate the catalyst/oxidant system by combining experiment and computer simulation in wastewater treatment.

Enhanced degradation of sulfamethoxazole by Fe-Mn binary oxide synergetic mediated radical reactions

In this study, a novel Fe-Mn binary oxide (FMBO), which combined the oxidation capability of iron and manganese oxides, was constructed to remove sulfamethoxazole (SMX) effectively using the simultaneous co-precipitation and oxidation methods, and the reaction products were probed by liquid chromatography-mass spectrometry (LC/MS). Particularly, FMBO-mediated transformation mechanisms of SMX were explored using radical scavengers and electron paramagnetic resonance (EPR). Results indicated that the best removal efficiency was obtained at a pH of 4.0, with the H₂O₂ of 6.0 mmol/L and the FMBO dosage of 2.0 g/L, giving 97.6% removal of 10 mg/L SMX within 60 min. More importantly, we found that the hydroxyl (•OH) radicals generated by FMBO through Fenton-like reaction were responsible for the SMX oxidation. EPR studies were confirmed that the peak intensities of hydroxyl adduct decreased remarkably with increasing pH values. Moreover, the four SMX degradation intermediate products were detected by LC/MS and a reaction pathway for the possible mineralization of SMX, with •OH radicals as the main oxidant, was proposed. These findings provide a novel insight into the removal of SMX by FMBO-mediated radical reactions in aquatic environments. Moreover, this research suggested that FMBO can act as an efficient catalyst to remove SMX in hospital wastewater.

Influence of industrial contamination in municipal secondary effluent disinfection by UV/H2O2

Advanced oxidation processes, including UV/H₂O₂, are methods able to remove diverse classes of organic contaminants and disinfect water and wastewater. However, the variation in the matrix composition can influence the inactivation of microorganisms due to the presence of competing reactive material, which consumes the available oxidants. This problem can lead to the use of inadequate oxidant/radiation dose and disturb a correct treatment. The aim of this study was to assess the efficiency of UV/H₂O₂ to inactivate microbiological indicators in secondary effluents in the presence of high concentration of carbonate, nitrate, metals, and industrial organic contaminants. Metals had a positive influence on inactivation acting as catalysts. Zn, Fe, and all metals simultaneously presented toxic effects to the indicator organisms in the higher concentrations before the treatment. Even in metals presence, the negative effect of carbonate and the industrial organic contaminants on indicators inactivation was very important. Bacteria regrowth after 72 h was also affected by the same inhibiting substances, but the metals acted positively inhibiting it. The disinfection indicators had different sensibilities to the spiked substances. Escherichia coli inactivation was more affected than total coliforms by the presence of the industrial contamination, which can lead to different interpretation of inhibition degree depending of the used disinfection indicator.

Vimentin disruption by lipoxidation and electrophiles: Role of the cysteine residue and filament dynamics

The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress, which induce extensive reorganization of the vimentin cytoskeletal network. Here, we have investigated the mechanisms underlying these effects. In vitro, electrophilic lipids, including 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal (HNE), directly bind to vimentin, whereas the oxidant diamide induces disulfide bond formation. Mutation of the single vimentin cysteine residue (Cys328) blunts disulfide formation and reduces lipoxidation by 15d-PGJ2, but not HNE. Preincubation with these agents differentially hinders NaCl-induced filament formation by wild-type vimentin, with effects ranging from delayed elongation and increased filament diameter to severe impairment of assembly or aggregation. Conversely, the morphology of vimentin Cys328Ser filaments is mildly or not affected. Interestingly, preformed vimentin filaments are more resistant to electrophile-induced disruption, although chemical modification is not diminished, showing that vimentin (lip)oxidation prior to assembly is more deleterious. In cells, electrophiles, particularly diamide, induce a fast and drastic disruption of existing filaments, which requires the presence of Cys328. As the cellular vimentin network is under continuous remodeling, we hypothesized that vimentin exchange on filaments would be necessary for diamide-induced disruption. We confirmed that strategies reducing vimentin dynamics, as monitored by FRAP, including cysteine crosslinking and ATP synthesis inhibition, prevent diamide effect. In turn, phosphorylation may promote vimentin disassembly. Indeed, treatment with the phosphatase inhibitor calyculin A to prevent dephosphorylation intensifies electrophile-induced wild-type vimentin filament disruption. However, whereas a phosphorylation-deficient vimentin mutant is only partially protected from disorganization, Cys328Ser vimentin is virtually resistant, even in the presence of calyculin A. Together, these results indicate that modification of Cys328 and vimentin exchange are critical for electrophile-induced network disruption.

Simultaneous removal of tetracycline and disinfection by a flow-through electro-peroxone process for reclamation from municipal secondary effluent

Pharmaceutical and personal care products as one of the micropollutants and bacteria in secondary effluent restrict the water reuse from municipal secondary effluent. Electro-peroxone (EP) process where H₂O₂ is generated in-situ by electrolysis is an emerging advanced oxidation process and an improvement of traditional peroxone method (O₃/H₂O₂). In this work, a flow-through EP process was compared with ozonation and electrolysis for simultaneous disinfection and degradation of tetracycline (TC). The disinfection effect by EP was higher than the sum of standalone ozone and electrolysis and the coupling coefficient of ozonation and electrolysis in EP process was 1.2. The flow-through EP system presented similar efficiency for separately and simultaneously treating E. coli and TC. For the actual secondary effluent treatment, trihalomethanes, haloacetonitrile and halonitromethanes, the main disinfection by-products, were much lower than the WHO's thresholds for drinking water. TOC and COD removal was 44% and 65%, respectively, at flow rate of 35 mL/min. BOD₅, bacteria, pH and other parameters in the effluent could satisfy the recreational landscape water quality standard, and the required energy consumption was 0.47 kW h/m³ at the flow rate 35 mL/min. Most of the degradation products were small-molecule organic acids, and possible degradation pathway of TC was suggested.

Oxidative degradation of chlorpyrifos using ferrate(VI): Kinetics and reaction mechanism

In this study, we investigated the degradation kinetics of chlorpyrifos, an organophosphorus (OP) compound, using ferrate(VI), and investigated the potential of this iron-based chemical oxidant on chlorpyrifos removal from water and wastewater treatments. A series of kinetic experiments were conducted to evaluate the influence of various environmental factors, such as pH, oxidant dosages, as well as the presence of anions, cations, humic acid (HA), and different water matrices. Chlorpyrifos was completely removed within 300 s under the following optimum conditions: [chlorpyrifos]₀ = 1 μM, [Fe(VI)]₀:[chlorpyrifos]₀ = 100:1, T = 25 °C, and pH = 7.0. Anions such as Cl^-, SO₄^2-, NO₃^-, and HCO₃^- and cations such as Fe³⁺, Cu²⁺, and NH₄⁺ did not appear to influence the removal of chlorpyrifos. However, the presence of Ca²⁺, Mg²⁺, and HA in water inhibited the degradation of chlorpyrifos. Experiments on removing chlorpyrifos from tap water, river water, and synthetic wastewater were performed to demonstrate the practical applications of Fe(VI). Ten oxidation products of chlorpyrifos were identified using liquid chromatography-quadrupole-time-of flight-mass spectrometry (LC-Q-TOF-MS), and their structures were further elucidated using MS/MS spectra. Then, two degradation pathways were preliminarily proposed including the oxidation of the P = S bond, cleavage of C-O bond, and hydroxyl substitution reaction. In general, Fe(VI) could be used as an efficient technology for chlorpyrifos removal from water and wastewater treatments.

Realizing 20% External Quantum Efficiency in Electroluminescence with Efficient Thermally Activated Delayed Fluorescence from an Exciplex

The investigation of nondoped exciplex blends of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T), working as the one-electron acceptor molecule, with different electron donors is reported. The emissions of these exciplexes span from the blue to orange-red regions, showing clear contribution from thermally activated delayed fluorescence (TADF) and delayed fluorescence originated from nongeminate recombination of charge carriers created by the dissociation of optically generated exciplexes. We focus our studies on the properties of TADF in these systems, covering in particular the physical meaning of the different transient components observed in their luminescence decays. Our results unravel the intricate role of reverse intersystem crossing due to spin-orbit coupling and possibly also due to hyperfine interactions and internal conversion, which affect the efficiency of the TADF mechanism. Remarkable performances are obtained in prototype organic light-emitting diodes fabricated with some of these blends. Green exciplex blends, in particular, exhibited the current efficiency of 60 cd A^-1, power efficiency of 71 lm W^-1, and external quantum efficiency of 20%. We believe that our results will contribute significantly to highlight the potential advantages of intermolecular exciplexes in the area of organic light-emitting diodes.