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Diospyros lotus L., which belongs to the Ebenaceae family, is used in folk medicine for treating anemia, fatigue, insomnia, and hepatitis. In the present study, supercritical CO2 fluid extraction (SFE) was used to extract Diospyros lotus L. essential oil, and its antioxidant, antimicrobial, and cytotoxic activities were investigated. The chemical composition of the essential oil was investigated using GC/MS. The antioxidant capacity was evaluated via 1,1diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging and hydroxyl radical scavenging. The minimum inhibitory concentration (MIC) using the broth microdilution method was applied to investigate antimicrobial activities. The cytotoxic activity of the essential oil was measured using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide (MTT) assay. The GC–MS analysis showed that Diospyros lotus L essential oil contained 25 components, mainly including 5-hydroxymethylfurfural (50.90%), 2-methylhexadecan-1-ol (19.97%), 2-cis-9-octadecenyloxyethanol (5.46%), dibutyl phthalate (4.84%), and n-hexadecanoic acid (4.20%). The IC50 values of the essential oil in the DPPH assay and hydroxyl radical scavenging activity were 46.46 ± 1.70 μg/mL and 0.551 ± 0.0267 mg/mL, respectively. Furthermore, at concentrations below 50 μg/mL, the evaluation of cell viability showed no cytotoxicity in the human embryonic kidney cell line 293T. The results show that Diospyros lotus L. essential oil has antimicrobial and antioxidant effects, and has no toxicity on 293T cells at low concentrations, indicating potential health benefits. [ABSTRACT FROM AUTHOR]

As reported, the persistent toxic and harmful pollutant bisphenol A (BPA) from industrial emissions has been consistently found in aquatic environments inhabited by humans. Periodate (PI)-based advanced oxidation processes (AOPs) have been employed to degrade BPA, although activating PI proves more challenging compared to other oxidants. A novel nano iron metal catalyst, sulfided nanoscale iron-nickel bimetallic nanoparticle supported on biocarbon (S-(nFe0-Ni)/BC) was synthesized and utilized to activate PI for the removal of BPA. The morphology, structure, and composition of S-(nFe0-Ni)/BC were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive spectrometer (SEM–EDS), and fourier-transform infrared spectrum (FTIR). The catalyst demonstrates an excellent ability to activate PI, achieving a BPA removal efficacy of 86.4%, accompanied by a 33% reduction in total organic carbon (TOC) in the {S-(nFe0-Ni)/BC}/PI system. BPA degradation exhibited a significant change at the 5-min mark. In the first stage (0–5 min), nonlinear dynamic fitting research, combined with scavenging experiments, unveiled the competitive degradation of pollutants primarily driven by iodate radical ( IO 3 · ), singlet oxygen 1 O 2 , and hydroxyl radical ( · OH ). The competitive dynamics aligned with the ExpAssoc model. The contribution rates of different active species during the second stage (5–120 min) were calculated. The contributions of main species to BPA removal follow the order of IO 3 · > 1 O 2 > · OH throughout the entire process. The influence of various parameters, such as the dosage of S-(nFe0-Ni)/BC, initial PI concentration, BPA concentration, pH, temperature, and the presence of coexisting anions, was also examined. Finally, a plausible reaction mechanism in the system is proposed, suggesting that the {S-(nFe0-Ni)/BC}/PI system involves a heterogeneous synergistic reaction occurring primarily on the surface of S-(nFe0-Ni)/BC. Therefore, this study proposes a promising approach for PI-based AOPs to degrade organic pollutants, aiming to mitigate the irreversible harm caused by such pollutants to organisms and the environment. [ABSTRACT FROM AUTHOR]

The efficient use of renewable X/γ-rays or accelerated electrons for chemical transformation of CO2 and water to fuels holds promise for a carbon-neutral economy; however, such processes are challenging to implement and require the assistance of catalysts capable of sensitizing secondary electron scattering and providing active metal sites to bind intermediates. Here we show atomic Cu-Ni dual-metal sites embedded in a metal-organic framework enable efficient and selective CH3OH production (~98%) over multiple irradiated cycles. The usage of practical electron-beam irradiation (200 keV; 40 kGy min−1) with a cost-effective hydroxyl radical scavenger promotes CH3OH production rate to 0.27 mmol g−1 min−1. Moreover, time-resolved experiments with calculations reveal the direct generation of CO2•‒ radical anions via aqueous electrons attachment occurred on nanosecond timescale, and cascade hydrogenation steps. Our study highlights a radiolytic route to produce CH3OH with CO2 feedstock and introduces a desirable atomic structure to improve performance. Most approaches for CH3OH production focus on thermochemical, electrolytic, and photolytic processes. Here the authors report a radiolytic route to produce CH3OH from CO2 and water by atomic Cu-Ni dual sites embedded in a metal-organic framework. [ABSTRACT FROM AUTHOR]

Radio-fluorogenic hydrogel dosimeters are urgently needed in radiotherapy for 3D dose verification. However, few hydrogel sensors have been reported at low absorbed doses under 2 Gy which meets the requirements of clinical practice. Here, we report a new type of gold-nanoparticle-enhanced radio-fluorogenic agarose hydrogel with coumarin as the dose-responsive material. An optimal composition of 3 wt% of agarose, 0.1 mM of gold nanoparticles, and 0.5 mM coumarin was selected. The addition of gold nanoparticles enhanced the hydroxyl radicals generated from the radiolysis of water, which can react with coumarin and generate fluorescent 7-hydroxy-coumarin and, eventually, achieve low-dose verification of 0–2.4 Gy with a high linear correlation coefficient. These findings provide an effective method for 3D dose verification, and will inspire the development of other radio-fluorogenic sensing hydrogels as well. [ABSTRACT FROM AUTHOR]

Owing to the easy over‐oxidation, it is a promising yet challenging task to explore renewable carbon resources to control the sunlight‐driven selective catalytic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF), producing important chemical feedstocks, namely, less‐oxidized 2,5‐diformylfuran (DFF) and 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA). Herein, we have developed a photocatalyst by anchoring a Ru complex on CdS quantum dots, which achieves selective oxidation of HMF toward DFF or HMFCA with high conversion (>81 %) and selectivity (>90 %), based on the controllable generation of two oxygen radicals under different atmospheres. Such selective conversion can also work well outside the laboratory by using natural sunlight. In particular, the selective production of HMFCA through photocatalytic HMF oxidation is achieved for the first time. More importantly, our photocatalyst is applicable for the selective oxidation of other compounds with hydroxyl and aldehyde groups. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) conversion of methane (CH4) has been extensively explored for the production of value‐added chemicals, yet remains a great challenge in high selectivity toward C2+ products. Herein, we report the optimization of the reactivity of hydroxyl radicals (.OH) on WO3 via facet tuning to achieve efficient ethylene glycol production from PEC CH4 conversion. A combination of materials simulation and radicals trapping test provides insight into the reactivity of.OH on different facets of WO3, showing the highest reactivity of surface‐bound.OH on {010} facets. As such, the WO3 with the highest {010} facet ratio exhibits a superior PEC CH4 conversion efficiency, reaching an ethylene glycol production rate of 0.47 μmol cm−2 h−1. Based on in situ characterization, the methanol, which could be attacked by reactive.OH to form hydroxymethyl radicals, is confirmed to be the main intermediate for the production of ethylene glycol. Our finding is expected to provide new insight for the design of active and selective catalysts toward PEC CH4 conversion. [ABSTRACT FROM AUTHOR]

Organic micro-pollutants such as pesticides and endocrine disruptors cause serious harm to human health and aquatic ecosystem. In this study, the potential degradation of atrazine (ATZ), triclosan (TCS), and 2,4,6-trichloroanisole (TCA) by UV-activated peroxydisulfate (UV/PDS) and UV-activated H2O2 (UV/H2O2) processes were evaluated under different conditions. Results showed that UV/PDS process was more effective than UV/H2O2 under the same conditions. Increasing oxidant dosage or decreasing the initial ATZ, TCS, and TCA concentrations promoted the degradation rates of these three compounds. The presence of natural organic matter (NOM) could effectively scavenge sulfate radical (SO4•−) and hydroxyl radical (HO•) and reduced the removal rates of target compounds. Degradation rates of ATZ and TCA decreased with pH increasing from 5.0 to 9.0 in UV/PDS process, while in UV/H2O2 process, the increase of solution pH had little effect on ATZ and TCA degradation. In the UV/PDS and UV/H2O2 oxidation process, when the solution pH increased from 5 to 8, the removal rates of TCS decreased by 19% and 1%, while when the solution pH increased to 9, the degradation rates of TCS increased by 23% and 17%. CO32−/HCO3− had a small inhibitory effect on ATZ and TCA degradation by UV/H2O2 and UV/PDS processes but promoted the degradation of TCS significantly (> 2 mM). Cl− had little effect on the degradation of ATZ, TCA, and TCS in UV/H2O2 process. Cl− significant inhibited on the degradation of ATZ and TCS, but the influence of Cl− on the degradation of TCA was weak in UV/PDS process. Based on these experimental results, the various contributions of those secondary radicals (i.e., carbonate radical, chlorine radical) were discussed. This study can contribute to better understand the reactivities when UV/PDS and UV/H2O2 are applied for the treatment of micro-pollutant-containing waters. [ABSTRACT FROM AUTHOR]

Graphical abstract Unsymmetrical squaraine dyes SQ-OPA can effectively identify Cys, Hcy and GSH through two response processes. Highlights • The property of unsymmetrical squaraine dyes is variable. • Acrylate groups changed the nature of the four-member ring of squaraine. • The central of squaraines plays a role in the identification of thiols. Abstract Two unsymmetrical squaraines (SQ-OH and SQ-OPA) have been synthesized. SQ-OPA was gained by esterification of acryloyl chloride and hydroxyl group on SQ-OH. Based on the investigation of the UV–vis, fluorescent, time-dependent 1H NMR and mass spectra, SQ-OPA was demonstrated to have two response sites to biothiols: the central four-member ring and acryloyl group. SQ-OPA is the first "turn-on" fluorescent squaraine thiol probe, and can probe the biothiols (Cys, Hcy, and GSH) simultaneously by naked-eye. However, SQ-OH bearing similar squaraine molecular framework with SQ-OPA, showed good chemical stability during the addition of biothiols. Therefore, for unsymmetrical squaraines, the substituent attached in benzene ring, far away from the central four-member ring, can signficantly affect the stability of squaraine central four-member ring against the nucleophilic attack, which could provide a new strategy for designing "turn-on" fluorescent SQ probes. [ABSTRACT FROM AUTHOR]

Recently, graphitized carbon nitride (g-C 3 N 4) is widely used as a metal-free photocatalyst for photocatalytic hydrogen peroxide (H 2 O 2) generation. However, its photocatalytic activity still suffers from the poor separation efficiency of charge carrier and weak adsorption ability towards dioxygen. Herein, a series of polydopamine (PDA) surface-modified g-C 3 N 4 composites (CNPX) are successfully fabricated through a self-assembled method. The optimum material, i.e. CNP40, produced H 2 O 2 of 69.0 μM/L under visible-light irradiation for 3 h, demonstrating 4.6-fold higher activity in comparison with the pristine g-C 3 N 4. Meanwhile, the apparent quantum yield (AQY) reached as high as 1.91% over CNP40 under monochromatic irradiation of 420 nm, which is 6.2-fold higher than CN. It is identified that the remarkably increased photocatalytic activity is contributed to the significantly promoted charge separation and dioxygen adsorption. This present work could provide a novel environmental-friendly material for the efficient photocatalytic H 2 O 2 production. • Loading PDA with various thickness on the surface of g-C 3 N 4 through simply adjusting the polymerization time of DA. • PDA's loading introduces rich hydroxyl group on the surface of CN/PDA-X catalyst. • The introduced hydroxyl group simultaneously promote charge-carriers separation and dioxygen adsorption. • The AQY over CN/PDA-40 reach as high as 1.91% at 420 nm, being 6.2 times higher than the pristine g-C 3 N 4. [ABSTRACT FROM AUTHOR]

BACKGROUD Nitrite is ubiquitous in natural water and wastewater. It is generally accepted that nitrite is an ozone consumer and has a negative influence on contaminants degradation during ozonation. Recently, nitrite was found to react with ozone to produce · OH. However, the potential positive effect of nitrite on the degradation of ozone refractory compounds has never been recognized previously during ozonation. Herein, the influence of nitrite on the degradation of atrazine by ozonation is evaluated. RESULTS The presence of nitrite was found to enhance atrazine degradation during ozonation. The enhancing effect of nitrite was attributed to · OH formation with a yield of 8.4% in the reaction of ozone with nitrite, which was demonstrated in scavenging experiments with tert-butyl alcohol. The maximum atrazine degradation was observed at the nitrite dose of 10 µmol L−1, when the ozone dose was 20 µmol L−1. The enhancing effect of nitrite on atrazine degradation by ozonation was more pronounced at lower pHs. The enhancing effect of nitrite on atrazine degradation by ozonation was still observed in surface water, especially at acidic pH. Six transformation products of atrazine were identified in the ozone/nitrite system, and the degradation mechanism is discussed. CONCLUSIONS This study is the first to demonstrate that nitrite not only acts as an ozone consumer, but may also have a positive effect on the degradation of ozone refractory contaminants by activating ozone to produce · OH. It provides a more comprehensive understanding to the role of nitrite in ozonation. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A rapid, simple, and sensitive spectrophotometric method was developed for the determination of persulfate in this study, based on the oxidation decolorization of methyl orange (MO) with sulfate radicals and hydroxyl radicals generated by the conjunction of persulfate with ferrous ions. The depletion of MO at its maximum absorption wavelength (507 nm) is in proportion to the concentration of persulfate in water. There was a good linear relationship (above 99%) between the depletion of MO and the concentration of persulfate in the ranges of 0.5–100 μmol L−1with a detection limit of 0.17 μmol L−1under the optimized conditions. The proposed MO method for the determination of persulfate in water was effective to tolerate the interferences of common coexisting foreign species in aqueous solutions. The results were as satisfactory as that obtained by the classical iodometric method used in practical water samples. Additionally, the proposed MO method is rather inexpensive to measure the concentration of persulfate by using standard laboratory instruments (spectrophotometer). [ABSTRACT FROM PUBLISHER]

2-methylisoborneol (2-MIB) and geosmin are two odor-causing compounds that are difficult to remove and the cause of many consumer complaints. In this study, we assessed the degradation of 2-MIB and geosmin using a UV/persulfate process for the first time. The results showed that both 2-MIB and geosmin could be degraded effectively using this process. The process was modeled based on steady-state assumption with respect to the odor-causing compounds and either hydroxyl or sulfate radicals. The second order rate constants for 2-MIB and geosmin reacting with the sulfate radical ( SO 4 − ) were estimated to be (4.2 ± 0.6) × 10 8 M −1 s −1 and (7.6 ± 0.6) × 10 8 M −1 s −1 respectively at a pH of 7.0. The contributions of the hydroxyl radical (OH ) to 2-MIB and geosmin degradation were 3.5 times and 2.0 times higher, respectively, than the contribution from SO 4 − in Milli-Q water with 2 mM phosphate buffer at pH 7.0. The pseudo-first-order rate constants ( k o s ) of both 2-MIB and geosmin increased with increasing dosages of persulfate. Although pH did not affect the degradation of 2-MIB and geosmin directly, different scavenging effects of hydrogen phosphate and dihydrogen phosphate resulted in higher values of k o s for both 2-MIB and geosmin in acidic condition. Bicarbonate and natural organic matter (NOM) inhibited the degradation of both 2-MIB and geosmin dramatically through consuming OH and SO 4 − and were likely to be the main radical scavengers in natural waters when using UV/persulfate process to control 2-MIB and geosmin. [ABSTRACT FROM AUTHOR]

Al2O3 or SiO2 particles with abundant surface hydroxyl groups can prevent side reactions of aromatic compounds with AlCl3 completely; this Lewis acid can potentially destroy the stable structure of aromatic compounds to a large extent. This discovery was successfully utilized in the highly efficient hydrogenation of benzene, toluene, and naphthalene under mild conditions co-catalyzed by AlCl3 and Pd/Al2O3 or Pd/SiO2. Pd, AlCl3, and the surface hydroxyl groups on the support show excellent cooperative effects for the hydrogenation reactions. Theoretical studies indicate that formation of a complex, by an interaction between benzene, AlCl3, and the solid oxides, plays a key role in the highly efficient hydrogenation reactions. [ABSTRACT FROM AUTHOR]

In order to enhance the Fenton oxidation of 2,4,6-trichlorophenol, copper ion was introduced to the Fenton reaction. The results show that, differing from ferrous ion, the copper ion exhibits no capability to decompose hydrogen peroxide to degrade the organic substrates; however, it can accelerate the degradation rate of 2,4,6-trichlorophenol by Fenton reaction, enhance the decomposition of hydrogen peroxide, increase the removal efficiency of TOC and release of chloride ion. Even lower copper ion dosage have significant enhancement on the degradation. The result of complete inhibition of the reaction by methanol and tert-Butanol suggests that hydroxyl radical is the most important reactive species in the Cu2+ enhanced Fenton reaction. [ABSTRACT FROM AUTHOR]

• In-situ generated FeO x and MnO x are used for membrane cleaning. • Flux recovery could be higher than 95% by the proposed method. • Efficient membrane cleaning are achieved by low H 2 O 2 dosage and short time. • PAC is a key factor for MnO x removal and membrane cleaning. Preoxidation-ultrafiltration process is an effective method for Fe2+ and Mn2+removal, in which Fe2+ (Mn2+) are firstly oxidized to FeO x (MnO x), then collected by the ultrafiltration membrane. However, the simultaneous presence of Fe2+, Mn2+, and organics in feed can cause severe membrane fouling, which inhibits the overall performance of this method prominently. In this study, a novel FeO x +MnO x +H 2 O 2 membrane cleaning method is proposed based on the idea of turning in-situ generated membrane foulants, i.e., FeO x +MnO x , into the catalysts for membrane cleaning. The results demonstrate that the FeO x +MnO x +H 2 O 2 system can achieve more than 95% membrane flux recovery and remove almost all irreversible membrane foulants within only 5 min and with only 0.5 % w t % H 2 O 2 solution. The outstanding performance of the system is mainly attributed to the catalytic decomposition of H 2 O 2 to generate both highly reactive radicals, such as hydroxyl radicals (·OH), and abundant oxygen. In addition, when the membrane is loaded by only MnO x , polyaluminium chloride (PAC) as the coagulator demonstrates prominent influence on the performance of membrane cleaning. However, PAC makes almost no contribution to membrane cleaning when the membrane is loaded by FeO x. This is because coagulation induced by PAC exerts more prominent impact on the particle size distribution of MnO x than that of FeO x. In conclusion, the catalytic decomposition of H 2 O 2 by in-situ generated FeO x +MnO x is a promising advanced oxidation process to achieve outstanding membrane cleaning performance under the condition of low H 2 O 2 concentration and no extra dosage of catalysts. The novel membrane cleaning system exhibits high potential for the practical membrane treatment processes to treat water with high contents of Fe and Mn. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • BQ improved efficiency of the Fe(III)/PMS system via boosting Fe(II) regeneration. • SO 4 •−, •OH and Fe(IV) simultaneously existed in the BQ/Fe(III)/PMS system. • Activation mechanism was clarified and degradation pathways were proposed. • Cl− inhibited ATZ degradation and caused chlorinated byproducts accumulation. Fe(II)-involved advanced oxidation processes could effectively degrade refractory contaminants, but the slow transformation of Fe(III) to Fe(II) limits their wide application. Herein we reported that p -benzoquinone (BQ) could accelerate Fe(III)/Fe(II) cycle and promote atrazine (ATZ) degradation in the Fe(III)/peroxymonosulfate (Fe(III)/PMS) system through reconstructing active Fe(II)/PMS system. Under the identical experimental conditions, ATZ degradation efficiency in the BQ/Fe(III)/PMS system (99.8%) was superior to that in the Fe(III)/PMS system (23.2%), suggesting the indispensable role of BQ in Fe(II) regeneration and PMS activation. Reactive species sulfate radical (SO 4 •−), hydroxyl radical (•OH) and ferryl ion (Fe(IV)) were involved in the BQ/Fe(III)/PMS system based on alcohol quenching experiments, ESR tests and the selective transformation from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO 2). ATZ degradation mechanism was proposed based on LC-MS detection, among which dealkylation and dechlorination-hydroxylation were the dominant transformation pathways. The BQ/Fe(III)/PMS system showed satisfactory catalytic performance at pH 2.5–7.0 and low Fe(III) concentration, which expanded the pH range and avoided the addition of a large amount of Fe. More importantly, the increase of PMS concentration not only enhanced the oxidative degradation of ATZ and its two main chlorinated byproducts (atrazine-desethyl (DEA) and atrazine-desisopropyl (DIA)), but also facilitated the removal of toxic BQ. Cl− inhibited the degradation of ATZ and caused the accumulation of DEA and DIA, and the higher Cl−, the more obvious this effect. This study provided a new approach to improve the Fe(III)/PMS system by boosting Fe(III)/Fe(II) cycle with quinons. [ABSTRACT FROM AUTHOR]

Abstract: Magnetic porous copper ferrite (CuFe2O4) showed a notable catalytic activity to peroxymonosulfate (PMS). More than 98% of atrazine was degraded within 15 min at 1 mM PMS and 0.1 g/L CuFe2O4. In contrast, CuFe2O4 exhibited no obvious catalytic activity to peroxodisulfate or H2O2. Several factors affecting the catalytic performance of PMS/CuFe2O4 were investigated. Results showed that the catalytic degradation efficiency of atrazine increased with PMS and CuFe2O4 doses, but decreased with the increase of natural organic matters concentration. The catalytic oxidation also showed a dependence on initial pH. The presence of bicarbonate stimulated atrazine degradation by PMS/CuFe2O4 at low concentrations but inhibited the degradation at high concentrations. Furthermore, the reactive species for atrazine degradation in PMS/CuFe2O4 system were identified as hydroxyl radical (HO ) and sulfate radical through competition reactions of atrazine and nitrobenzene, instead of commonly used alcohol scavenging, which was not a reliable method in metal oxide catalyzed oxidation. Surface hydroxyl groups of CuFe2O4 were a critical part in radical generation and the copper on CuFe2O4 surface was an active site to catalyze PMS. The catalytic degradation of atrazine by PMS/CuFe2O4 was also effective under the background of actual waters. [Copyright &y& Elsevier]

Many experiments have demonstrated that KI/hydroxyl (–OH) substance catalytic systems are very effective for the cycloaddition of CO2 with epoxides to produce cyclic carbonates, which is among the most successful and important routes to convert CO2 into value-added chemicals. But the catalytic mechanism is not clear. In this work, we conducted the first theoretical research to clarify the catalytic mechanism of KI and the co-catalytic mechanism of hydroxyl substances. Density functional theory (DFT) method was used, propylene oxide (PO) was selected as the epoxide, and glycerol and propylene glycol (PG) as the hydroxyl substances. The transition structures, rate-determining steps and lowest energy barrier reaction pathways were identified for both gas phase and solvent environments. It was found that the hydroxyl groups, the potassium cation and the iodine anion form a ternary synergistic catalytic system, I−–(–OH)–K+. The polar solvent environment provided by the hydroxyl substance was also favorable to the cycloaddition reaction. The results provide a clear profile for the cycloaddition of CO2 and epoxides promoted by KI/hydroxyl substance catalytic systems, and can explain satisfactorily the previous experimental observations. [ABSTRACT FROM AUTHOR]

In order to increase the reaction rate of the heterogeneous Fenton-like, the catalyst FeIV F = O/R was used to catalytically decompose H2O2 for the removal of Orange IV in aqueous solution. The effect of initial pH, temperature, initial H2O2 concentration and initial Orange IV concentration on the reaction rate was discussed. It is found that the reaction rate decreases with the increase of pH. The degradation of Orange IV can be effective at pH range of 3-10. This reaction follows pseudo -- first -- order kinetics. The activation energy for FeIV F/R catalyzed oxidation of Orange IV is determined to be 59.94 kJ/mol. The reaction rate is positively proportional to initial H2O2 concentration and initial Orange IV concentration respectively. Repeated use of catalyst does not decrease the removal rate of Orange IV. [ABSTRACT FROM AUTHOR]

In order to increase the reaction rate of the heterogeneous Fenton -- like, the catalyst FemIII was used to catalytically decompose H2O2 under visible light for the removal of Malachite Green (MG) in aqueous solution. The effect of initial pH, initial H2O2 concentration, initial MG concentration and t -- butanol on the reaction rate was also discussed. The result shows that the visible light can enhance the degradation of MG. The experiment of t -- butanol shows that the ferryl iron and hydroxyl radical coexist in the system. Repeated use of catalyst does not decrease the removal rate of MG. [ABSTRACT FROM AUTHOR]

Selecting nitrobenzene as a model compound, the assistance of magnesium cations on ozon ation of refractory organic pollutant was investigated in pure water background. It is interesting to find that the presence of magnesium cations with a level of tens of millimoles per liter can obviously increase the degradation and mineralization efficiency of nitrobenzene compared with the case of ozonation alone. At lower pH condition, the magnesium cations still effectively assisted the ozonation of nitrobenzene. Ozone decomposition was accelerated by the presence of magnesium cations. It was confirmed that the presence of magnesium cations promoted the generation of hydroxyl radicals. It was speculated that the formation of hydroxyl group by the deprotonation of the hexaqueous magnesium cations complex Mg[H2O]62+ promoted the hydroxyl radical formation. However, the promotion was found to be unremarkable and should not be the sole reason for the assistance of magnesium cations on ozonation. The complexation reaction between the hexaqueous magnesium cations complex and carboxylic group may be part of the reason for the magnesium cation- assisted ozonation of organic pollutants. This finding will provide fundamental support for the applications of ozone to treat the concentrated water from membrane filtration which contains both high concentration of magnesium cations and organic pollutants. [ABSTRACT FROM AUTHOR]

Abstract: The experiments have been performed with a semi-continuous batch reactor to investigate the degradation efficiency of nitrobenzene in aqueous solution by ultrasound with the different orthogonal dual frequencies catalytic ozonation. The introduction of ultrasound can enhance the degradation efficiency of nitrobenzene compared to the results obtained from the processes of ozonation alone and ultrasound alone. The degradation of nitrobenzene is found to be zero-order in the two systems of ultrasound alone, and the reactions follow the pseudo-first-order kinetic model in the processes of ozone alone and ozone/ultrasound. The investigation confirms that the degradation of nitrobenzene follows the mechanism of hydroxyl radical (•OH) oxidation, and the enhancement function is even more pronounced in the presence of ultrasound with the greater difference between the orthogonal dual frequencies due to the obvious synergetic effect between ozone and ultrasound, which increases the utilization efficiency of ozone, and accelerates the initiation of •OH and the formation of H2O2, resulting in the rapid formation of an increasing diversity of byproducts and the advancement degree of mineralization of total organic carbon (TOC). The oxidative byproducts have been, respectively identified in the different processes selected, including o, p, m-nitrophenols, phenol, malonic acid, 4-nitrocatechol, nitrate ion, maleic acid, oxalic acid, hydroquinone, p-quinone, 1,2,3-trihydroxy-5-nitrobenzene and acetic acid. [Copyright &y& Elsevier]

2-Methylisoborneol (MIB) is a terpenoid produced as a secondary metabolite by some cyanobacteria and actinomycetes and thus can be present in some drinking water source waters. The removal efficiency, products, and degradation pathway of MIB in drinking water by ozonation were studied. The results showed that ozone is efficient in removing MIB from an aqueous solution, regardless of the initial MIB concentration. Hydroxyl radicals (·OH) scavenger experiments indicated that hydroxyl radicals are involved in MIB degradation. The degradation products of MIB were identified by gas chromatography-mass spectrometry. Camphor was identified as a primary degradation product, which was further oxidized to form other degradation intermediates, such as aldehydes, ketones, and carboxylic acids. A possible degradation pathway for the ozonation of MIB was proposed. Qualitative and quantitative analysis of the formation of aldehydes was carried out. It was found that six aldehydes are the main aldehydes products of ozonation of MIB, namely formaldehyde, acetaldehyde, propanal, butanal, glyoxal, and methyl glyoxal. [ABSTRACT FROM AUTHOR]

Removal of phosphate in secondary effluents was investigated in presence of Fe2+/H2O2. The effect of H2O2-dose, Fe-dose and initial phosphate concentration were assessed. The results indicated that Fe2+/H2O2 could greatly increase the removal of phosphate compared with those achieved by Fe2+ alone. For initial phosphate concentration of 0.97–3.75mg P/L, phosphate removal rates of 50–60% were observed at 1:1 molar addition of Fe(II). However, a 125% excess of Fe-dose was necessary for complete phosphate removal. The experimental data demonstrated that removal of phosphate with Fe2+/H2O2 was higher than that observed with ferric coagulation alone. This fact suggested that in situ formed Fe(III) having much affinity for ligand phosphate. Chemical co-precipitation was considered as the dominant mechanism about phosphate removal in presence of Fe2+/H2O2. The electron paramagnetic resonance (EPR) spectra tests in secondary effluents showed that Fe2+/H2O2 could produce an increasing hydroxyl radical concentration with a decrease in both H2O2 dosage and phosphate concentration. Fe2+/H2O2 had the potential to be utilized for removal of phosphate due to the lower cost and the higher phosphate removal capability. [Copyright &y& Elsevier]

Abstract: The degradation efficiencies of nitrobenzene in aqueous solution were investigated by semi-continuous experiments in the processes of ozone alone, ozone/ceramic honeycomb (CH) and ozone/modified ceramic honeycomb (MCH). MCH with 1.0% Mn and 0.5% Cu had more pronounced catalytic ability than CH to accelerate the degradation of nitrobenzene, to increase the utilization efficiency of ozone, to improve the concentrations of hydrogen peroxide (H2O2) formation and hydroxyl radical (ation, and to enhance the removal efficiency of TOC. The modification process of CH with the metals enhanced the density of surface hydroxyl groups, which determines the initiation of zone decomposition and the generation of intermediate species on heterogeneous catalytic surface, yielding the acceleration of the degradation of nitrobenzene in aqueous solution. Possible reaction mechanism of ozone with heterogeneous catalytic surface in aqueous solution was proposed, and the formation mechanism of H2O2 and so discussed according to the combined reactions in heterogeneous and homogeneous catalytic systems. [Copyright &y& Elsevier]

The O3/PMS system has appeared as an effective wastewater treatment method because of the simultaneous generation of hydroxyl radicals (•OH) and sulfate radicals (SO4•−). Many research achievements have been made on the degradation of micropollutants and the reaction mechanism of the O3/PMS system. However, an integral understanding of the O3/PMS system is lacking, which limits the development of safe and effective AOP-based water treatment schemes. Therefore, in this review, the degradation effects, toxicity changes, and reaction mechanisms of various micropollutants in the O3/PMS system are reviewed. The formation of oxidation by-products (OBPs) is an important issue that affects the practical application of O3/PMS systems. The formation mechanism and control methods of OBPs in the O3/PMS system are overviewed. In addition, the influence of different reaction conditions on the O3/PMS system are comprehensively evaluated. Finally, future research needs are proposed based on the limited understanding of O3/PMS systems in the degradation of micropollutants and formation of OBPs. Specifically, the formation rules of several kinds of OBPs during the O3/PMS system are not completely clear yet. Furthermore, pilot-scale research, the operational costs, sustainability, and general feasibility of the O3/PMS system also need to be studied. This review can offer a comprehensive assessment on the O3/PMS system to fill the knowledge gap and provide guidance for the future research and engineering applications of the O3/PMS system. Through this effort, the O3/PMS system can be better developed and turned towards practical applications. [ABSTRACT FROM AUTHOR]

Among the radicals (hydroxyl radical (•OH), hydrogen atom (H•), and solvated electron (esol−)) that are generated via water radiolysis, •OH has been shown to be the main transient species responsible for radiation damage to DNA via the indirect effect. Reactions of these radicals with DNA-model systems (bases, nucleosides, nucleotides, polynucleotides of defined sequences, single stranded (ss) and double stranded (ds) highly polymeric DNA, nucleohistones) were extensively investigated. The timescale of the reactions of these radicals with DNA-models range from nanoseconds (ns) to microseconds (µs) at ambient temperature and are controlled by diffusion or activation. However, those studies carried out in dilute solutions that model radiation damage to DNA via indirect action do not turn out to be valid in dense biological medium, where solute and water molecules are in close contact (e.g., in cellular environment). In that case, the initial species formed from water radiolysis are two radicals that are ultrashort-lived and charged: the water cation radical (H2O•+) and prethermalized electron. These species are captured by target biomolecules (e.g., DNA, proteins, etc.) in competition with their inherent pathways of proton transfer and relaxation occurring in less than 1 picosecond. In addition, the direct-type effects of radiation, i.e., ionization of macromolecule plus excitations proximate to ionizations, become important. The holes (i.e., unpaired spin or cation radical sites) created by ionization undergo fast spin transfer across DNA subunits. The exploration of the above-mentioned ultrafast processes is crucial to elucidate our understanding of the mechanisms that are involved in causing DNA damage via direct-type effects of radiation. Only recently, investigations of these ultrafast processes have been attempted by studying concentrated solutions of nucleosides/tides under ambient conditions. Recent advancements of laser-driven picosecond electron accelerators have provided an opportunity to address some long-term puzzling questions in the context of direct-type and indirect effects of DNA damage. In this review, we have presented key findings that are important to elucidate mechanisms of complex processes including excess electron-mediated bond breakage and hole transfer, occurring at the single nucleoside/tide level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Enhanced degradation of OCs was obtained by TAP in the presence of Cl−. • Different reactive species contributed to OCs degradation during Cl−/TAP oxidation. • TOC removal efficiencies were 52.6 %–69.0 % using TAP in the existence of Cl−. • The concentrations of typical CBPs were 17.2 μg/L–86.3 μg/L in Cl−/TAP system. The effect of chloride ion (Cl−) on the degradation of organic contaminants (OCs) by thermally activated peroxymonosulfate (TAP) was assessed in this study. P -aminobenzoic acid (PABA), sulfadiazine (SDZ), bisphenol A (BPA), and chloramphenicol (CAP) were employed as model OCs with different structure. The degradation efficiencies of PABA, SDZ, BPA, and CAP were respectively 76.4 %, 90.8 %, 10.1 %, and 14.5 % by TAP (70 °C) after 60 min treatment, further raised to 97.6 %, 97.4 %, 55.2 %, and 30.5 % in the presence of Cl− (1 mM). When Cl− concentration increased to 10 mM, PABA and SDZ were completely degraded respectively after 7 min and 10 min, 97.1 % of BPA and 59.5 % of CAP were removed within 60 min. In TAP system, PABA and SDZ were primarily degraded by direct peroxymonosulfate (PMS) oxidation, while BPA and CAP were mostly removed by hydroxyl radical and sulfate radical oxidation. In Cl−/TAP mixtures, the degradation of PABA and BPA was mainly attributed to hypochlorous acid oxidation, SDZ was chiefly removed via direct PMS oxidation, and CAP was principally oxidized by radicals. Furthermore, the intermediate products of OCs degradation during Cl−/TAP oxidation were identified, and primary degradation pathways were proposed. The removal efficiencies of total organic carbon were markedly improved from 19.3 % to 25.3 % by TAP to 52.6 %–69.0 % in Cl/TAP system. The concentrations of typical chlorinated by-products after OCs oxidation were 17.2 μg/L–86.3 μg/L in Cl−/TAP system. Considering the complexity of actual wastewater, 51.3 %–100 % removal efficiencies of OCs by TAP oxidation were achieved in Cl−-containing secondary effluent. Understanding the role of Cl− in OCs degradation is essential for the practical application of Cl−/TAP oxidation in advanced wastewater treatment. [ABSTRACT FROM AUTHOR]

This study presents a catalytic membrane based on cobalt-loaded carbon nanotubes and graphene oxide (Co@CNT-GO). Cobalt, serving as the active center, efficiently activates peroxymonosulfate for the degradation of organic compounds in transmembrane water. The uniform dispersion and firm loading of Co on CNT prevent the aggregation and leakage issues typically associated with conventional catalysts. The two-dimensional channels formed by the vacuum-assisted self-assembly of CNT and GO enhance the probability of contact between organic compounds and Co and prolong the contact duration thereby ensuring catalytic efficiency while maintaining a low water permeability resistance. The water flux of the catalytic membrane is 90 L/m2/h, and the atrazine removal efficiency is more than 92%, maintaining high stability even after continuous operation for 72 h. The generated active free radicals, including sulfate radicals, hydroxyl radicals, and singlet oxygen, synergistically facilitate the mineralization of organic compounds. Furthermore, the presence of oxygen vacancies on CNT accelerates the redox cycle of ≡ Co(II)/≡Co(III), sustaining the catalytically active center. Compared to the precursor catalytic membrane, Co@CNT-GO catalytic membrane possesses the characteristics of high removal efficiency and high flux, holding promise as a platform technology for the rapid and precise treatment of organic pollutants in contaminated water. [Display omitted] • Membranes are prepared via vacuum-assisted self-assembly of Co@CNT-GO. • Catalytic oxidation process occurs in 2D nanochannels filled with 1D nanotubes. • Co@CNT-GO membrane achieves almost 100% removal of ATZ within 175 ms. • Oxygen vacancies accelerate the redox cycle of ≡ Co(II)/≡Co(III). [ABSTRACT FROM AUTHOR]

• The simulated sunlight/monochloramine system effectively degraded microcontaminants. • The established model well simulated roles of Cl∙, HO∙, Cl 2 ∙−, and photodegradation. • Cl∙ and HO∙ were main radicals responsible for degrading ibuprofen and carbamazepine. • DBPs were analyzed at different reaction times and after 24 h of post-chloramination. As an eco-friendly and sustainable energy, solar energy has great application potential in water treatment. Herein, simulated sunlight was for the first time utilized to activate monochloramine for the degradation of environmental organic microcontaminants. Various microcontaminants could be efficiently degraded in the simulated sunlight/monochloramine system. The average innate quantum yield of monochloramine over the wavelength range of simulated sunlight was determined to be 0.068 mol/Einstein. With the determined quantum yield, a kinetic model was established. Based on the good agreement between the simulated and measured photolysis and radical contributions to the degradation of ibuprofen and carbamazepine, the major mechanism of monochloramine activation by simulated sunlight was proposed. Chlorine radical (Cl∙) and hydroxyl radical (HO∙) were major radicals responsible for microcontaminant degradation in the system. Moreover, the model facilitated a deep investigation into the effects of different reaction conditions (pH, monochloramine concentration, and water matrix components) on the degradation of ibuprofen and carbamazepine, as well as the roles of the involved radicals. The differences between simulated and measured degradation data of each microcontaminant under all conditions were less than 10 %, indicating the strong reliability of the model. The model could also make good prediction for microcontaminant degradation in the natural sunlight/monochloramine system. Furthermore, the formation of disinfection byproducts (DBPs) was evaluated at different oxidation time in simulated sunlight/monochloramine with and without post-chloramination treatment. In real waters, organic components showed more pronounced suppression on microcontaminant degradation efficiency than inorganic ions. This study provided a systematic investigation into the novel sunlight-induced monochloramine activation system for efficient microcontaminant degradation, and demonstrated the potential of the system in practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

To better predict the elimination of highly ozone-refractory organic micro-pollutants from wastewater in ozonation and peroxone (O 3 /H 2 O 2 ) processes, it is important to understand the OH formation therein. Nevertheless, the contribution of the propagation reactions (in brief, OH + DOM (Dissolved Organic Matter) + O 2 → O 2 − , O 3 + O 2 − → O 3 − → OH ) to the OH yields ( Ф ) in these two processes has not received great attention so far. In this study, >25% of O 3 was estimated to be consumed via the propagation reactions in ozonation of wastewater effluents. The competition method (taking the OH exposure and scavenging capacity of water matrix into account) was recommended to determine the Ф values, and thus the relatively higher values (i.e., 33–58% vs. 6–24%) in ozonation were obtained as compared with the “ tert- Butanol ( t BuOH) assay” (with excess t BuOH to scavenge OH producing stoichiometric formaldehyde), where the contribution of the propagation reactions was otherwise neglected when excess t BuOH completely scavenged OH . In peroxone of wastewater effluents, the rate constant of O 3 consumption increased significantly with the increase of H 2 O 2 concentration ([H 2 O 2 ]:[O 3 ] = 0.1–0.35). However, compared to ozonation alone, the improvement of the Ф values was negligible over a wide range of [H 2 O 2 ]:[O 3 ] = 0.1–2.0. This discrepancy was mainly ascribed to the fact that substantial O 3 consumption via the propagation reactions resulted in comparable Ф values in peroxone vs. ozonation processes. [ABSTRACT FROM AUTHOR]

The use of vacuum-ultraviolet (VUV) photolysis in water treatment has been gaining significant interest due to its efficacy in degrading refractory organic contaminants and eliminating oxyanions. In recent years, the reactive species driving pollutant decomposition in VUV-based advanced oxidation and reduction processes (VUV-AOPs and VUV-ARPs) have been identified. This review aims to provide a concise overview of VUV photolysis and its advancements in water treatment. We begin with an introduction to VUV irradiation, followed by a summary of the primary reactive species in both VUV-AOPs and VUV-ARPs. We then explore the factors influencing VUV-photolysis in water treatment, including VUV irradiation dose, catalysts or activators, dissolved gases, water matrix components (e.g., DOM and inorganic anions), and solution pH. In VUV-AOPs, the predominant reactive species are hydroxyl radicals (˙OH), hydrogen peroxide (H 2 O 2), and ozone (O 3). Conversely, in VUV-ARPs, the main reactive species are the hydrated electron (e aq −) and hydrogen atom (˙H). It is worth noting that VUV-based advanced oxidation/reduction processes (VUV-AORPs) can transit between VUV-AOPs and VUV-ARPs based on the externally added chemicals and dissolved gases in the solution. Increase of the VUV irradiation dose and the concentration of catalysts/activators enhances the degradation of contaminants, whereas DOM and inorganic anions inhibit the reaction. The pH influences the redox potential of ˙OH, the speciation of contaminants and activators, and thus the overall performance of the VUV-AOPs. Conversely, an alkaline pH is favored in VUV-ARPs because e aq − predominates at higher pH. [Display omitted] • VUV photolysis includes AOP driven by ˙OH, H 2 O 2 , and O 3 , and ARP driven by e aq − /˙H. • Irradiation dose, catalysts, gas, water matrix, and pH influences VUV efficacy. • VUV-AOP cost is lower than ultrasound, UV, electric AOP, plasma, and photo-Fenton. • Shallow penetration depth of VUV in water leads to full-scale treatment unworkable. • Optimizing the VUV reactor is a good way to overcome its limitations. [ABSTRACT FROM AUTHOR]

Establishing an economic and sustained Fenton oxidation system to enhance sludge dewaterability and carbamazepine (CBZ) removal rate is a crucial path to simultaneously achieve sludge reduction and harmless. Leveraging the principles akin to "tea making", we harnessed tea waste to continually release tea polyphenols (TP), thus effectively maintaining high level of oxidation efficiency through the sustained Fenton reaction. The results illustrated that the incorporation of tea waste yielded more favorable outcomes in terms of water content reduction and CBZ removal compared to direct TP addition within the Fe(III)/hydrogen peroxide (H 2 O 2) system. Concomitantly, this process mainly generated hydroxyl radical (•OH) via three oxidation pathways, effectively altering the properties of extracellular polymeric substances (EPS) and promoting the degradation of CBZ from the sludge mixture. The interval addition of Fe(III) and H 2 O 2 heightened extracellular oxidation efficacy, promoting the desorption and removal of CBZ. The degradation of EPS prompted the transformation of bound water to free water, while the formation of larger channels drove the discharge of water. This work achieved the concept of treating waste with waste through using tea waste to treat sludge, meanwhile, can provide ideas for subsequent sludge harmless disposal. [Display omitted] • The concept of tea-making is utilized for improving Fe(III)/H 2 O 2 oxidation ability. • The sustained release of tea polyphenols maintains efficient cycle of Fe(II)/Fe(III). • The destruction of hydrogen bond and sustained oxidation leads to CBZ removal. • Extracellular oxidation promotes the desorption of CBZ from EPS-CBZ complex. [ABSTRACT FROM AUTHOR]

• Cl 2 •− was an important parent radical of HO• in the presence of chloride. • The k Cl2•−, HCO3− and k Cl2•−, CO32− were determined by laser flash photolysis. • The accuracy and applicability of the kinetic model were greatly improved. • Chloride could compensate the inhibitory effect of bicarbonate on HO• generation. The ultraviolet/monochloramine (UV/NH 2 Cl) process is an emerging advanced oxidation process with promising prospects in water treatment. Previous studies developed kinetic models of UV/NH 2 Cl for simulating radical concentrations and pollutant degradation. However, the reaction rate constants of Cl 2 •− with bicarbonate and carbonate (k Cl2•−, HCO3− and k Cl2•−, CO32−) were overestimated in literature. Consequently, when dosing 1 mM chloride and 1 mM bicarbonate, the current models of UV/NH 2 Cl severely under-predicted the experimental concentrations of three important radicals (i.e., hydroxyl radical (HO•), chlorine radical (Cl•), and dichloride radical (Cl 2 •−)) with great deviations (> 90 %). To investigate this issue, the transformation reactions among these three radicals in UV/NH 2 Cl were systematically studied. For the first time, it was found that in addition to Cl•, Cl 2 •− was also an important parent radical of HO• in the presence of chloride, and chloride could effectively compensate the inhibitory effect of bicarbonate on HO• generation in the system. Moreover, reactions and rate constants in current models were scrutinized from corresponding literature, and the reaction rate constants of Cl 2 •− with bicarbonate and carbonate (k Cl2•−, HCO3− and k Cl2•−, CO32−) were reevaluated to be 1.47 × 105 and 3.78 × 106 M−1s−1, respectively, by laser flash photolysis. With the newly obtained rate constants, the refined model could accurately simulate concentrations of all three radicals under different chloride and bicarbonate dosages with satisfactory deviations (< 30 %). Meanwhile, the refined model performed much better in predicting pollutant degradation and radical contribution compared with the unrefined model (with the previously estimated k Cl2•−, HCO3− and k Cl2•−, CO32−). The results of this study enhanced the accuracy and applicability of the kinetic model of UV/NH 2 Cl, and deepened the understanding of radical transformation in the process. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the synergistic and antagonistic effects of Fe species and coexisting natural organic matter (NOM) on the efficacy of solar light disinfection of water are investigated. Different initial iron species (Fe2+/Fe3+) and naturalorganic matter types (Suwannee River-SRNOM, Nordic Reservoir NOM-NDNOM, SR Humic Acid-SRHA, and SR Fulvic Acid-SRFA) were selected. The bactericidal actions of Fe and NOM, alone or in conjunction, were evaluated at various initial iron dosing concentrations, NOM concentrations, irradiation intensities, and pH values. We show that when an appropriate iron (1 ppm Fe2+ or 0.25 ppm Fe3+) and NOM concentration (2 ppm SRNOM or 5 ppm NDNOM) coexisted, synergistic inactivation was observed in the pH range 5.0–8.0. A plausible explanation is that the presence of Fe+NOM significantly promoted the generation of hydroxyl radicals (•OH) and singlet oxygen (1O 2), which led to enhanced disinfection rates. These results elucidate the previously understudied effects of ubiquitous elements in natural waters and their impact on solar-mediated bacterial inactivation. [Display omitted] ● We analyzed the synergistic disinfection effects between Fe and NOM in sunlit waters. ● Various types of Fe and NOM reveal different synergistic capacity under varied pH. ● The coexistence of Fe and NOM in water enhances the Fe2+/Fe3+ cycling and PPRI production. ● 1O 2 is a key mediator of the bacterial inactivation under solar exposure. [ABSTRACT FROM AUTHOR]

[Display omitted] • The addition of In 2 O 3 significantly enhanced the visible light response of Mn(VII) • Intermediate Mn int (Mn(V) and Mn(III)) and •OH were identified as the major oxidants. • Scavenging of photogenerated e- by Mn(VII) contributed to the generation of Mn int. • The reaction of photogenerated h+ with H 2 O contributed to the generation of •OH. • The Vis/In 2 O 3 /Mn(VII) process demonstrated good reusability and robust resistance to water matrices. Activation of permanganate (Mn(VII)) by generating intermediate manganese species (Mn int , i.e., Mn(V) and Mn(III)) has been demonstrated to be an efficient way to enhance the oxidative ability of Mn(VII). In this work, it was found that the addition of indium oxide (In 2 O 3) could significantly enhance the visible light response of Mn(VII) (Vis/In 2 O 3 /Mn(VII)) by selecting flumequine (FLU) as a representative compound. The presence of In 2 O 3 enhanced the degradation of FLU by the Vis/Mn(VII) process with the pseudo-first-order rate constant increasing by around 30 folds. Intermediate Mn int (Mn(V) and Mn(III)) and hydroxyl radicals (•OH) were identified as the major oxidants in the Vis/In 2 O 3 /Mn(VII) process, and •OH outcompeted that of Mn int under alkaline conditions. The scavenge of photogenerated e- by Mn(VII) played a critical role in the generation of Mn int , while the reaction of photogenerated h+ with H 2 O contributed to the generation of •OH. The degradation efficiency of FLU showed a negative relationship with the increase of solution pH, likely due to the electrostatic repulsion between the deprotonated FLU and negatively charged In 2 O 3 surfaces. Increasing Mn(VII) or In 2 O 3 dosages enhanced the degradation of FLU by elevating the concentrations of reactive species. The presence of chloride, bicarbonate, and humic acid slightly inhibited FLU degradation by the Vis/In 2 O 3 /Mn(VII) process, due to their competitive scavenging of reactive species. Totally 14 oxidation products were identified during FLU oxidation by the Vis/In 2 O 3 /Mn(VII) process, and they were likely generated via hydroxylation, defluorination, dealkylation/decarboxylation/deamination, ring-opening, or oxidation pathways. Good stability and reusability of the In 2 O 3 catalyst were obtained. This work proposed a new activation pathway for Mn(VII) and provided a novel approach for the treatment of emerging contaminants in aqueous environments. [ABSTRACT FROM AUTHOR]

Rapid self-decomposition and low reactivity to natural organic compounds with more unsaturated functional groups in alkaline water were the two critical parameters that restricted the practical application of Ferrate (VI). Herein, we reported a novel approach to reactivate the stabilized Fe (VI) for highly efficient membrane cleaning. The Fe (VI) stabilized by bicarbonate/carbonate (HCO 3 −/CO 3 2−) buffer was reactivated by calcium ions (Ca2+) to facilitate releasement of O 2 and generate high-valent iron species with subsequent hydroxyl radicals (•OH). The process was rationally utilized for removal of the membrane foulants, humic acid (HA) coupled with Ca2+, which exhibited excellent cleaning performance with membrane flux recovered from 67% to 98%. The outstanding removal performance of membrane foulants could be mainly attributed to the high-valent iron species and •OH, with their contribution rate ratio being about 7:3. Significantly, the proposed FeO 4 2− + HCO 3 −/CO 3 2− buffer + Ca2+ strategies paved a novel way for upgrading the Fe(VI) utilization pattern compared with Fe(VI) direct oxidation, which was expected to provide an effective option for Fe(VI)-based membrane cleaning in alkaline water. [Display omitted] • A novel cleaning strategy in alkaline condition using Fe (VI) was proposed. • The stabilized Fe (VI) was reactivated by Ca2+ to facilitate releasement of O 2. • Ca2+ could activate stabilized ferrate (VI) for effective membrane cleaning. • High-valent iron species and.•OH radicals were the reactive species for cleaning process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bifunctional core–shell V O -LCO@CeO x nanoreactor was designed for H 2 O 2 activation. • Heterostructure boosted V O levels via the removal of oxygen atoms to interface. • Direct electron transfer between ≡Cu and ≡Ce achieved efficient ROS production. • The catalytic mechanism had been further confirmed through DFT calculations. Double oxygen vacancies (V O) tuned core–shell La V CuO δ @CeO x (V O -LCO@CeO x) nanoreactors with direct electron transfer (DET) structure was synthesized as an effective heterogeneous Fenton-like catalyst for the quinoline removal. The DET structure was constructed by electron-rich ≡Cu center of V O -LCO core and electron-capture center of CeO x shell for electrons supplying and consuming. This structure elevated total V O levels of catalyst through the removal of oxygen atoms in CeO 2 from attice to interface sites. Meanwhile, the ≡Ce(III) acted as reactive sites for the adsorption of hydrogen peroxide (H 2 O 2) to form surface peroxide species, and then the electron-rich ≡Cu center was further provided electrons to surface peroxide species by DET to produce hydroxyl radical. Moreover, the newly formed surface V O would also be further promote hydroxyl radical production through self-activation of H 2 O 2. This catalyst displayed excellent catalytic activity and stability. The density functional theory (DFT) results further pointed out that this structure had excellent adsorption energy, and generable electron transfer from V O -LCO to CeO x. This work provided a novel approach for the development of heterogeneous Fenton-like catalysts to degrade quinoline wastewater. [ABSTRACT FROM AUTHOR]

Organic degradation by zero-valent metal (ZVM)-activated peroxymonosulfate (PMS) systems has drawn great attention in water treatment. Among various types of ZVM, zero-valent copper (ZVC) showed greatest activating capacity. However, the disadvantages of the released Cu2+ limit the practical utilization of ZVC. In this study, the activation capacity of four normal-sized copper catalysts, namely, copper sheet, graphene-copper sheet, copper foam, and graphene-copper foam, for PMS was investigated using Naproxen (NPX) as the probe compound. Results showed that the degradation efficiency of NPX increased by 10%, while the release of Cu2+ decreased by 30% by coating the copper with graphene. Stability tests showed that all of the four catalysts exhibited considerable stability in PMS activation. Furthermore, we found for the first time that the hydroxyl radical was the dominant species in the degradation of NPX rather than the sulfate radical, which was proved by ESR and radical scavenging experiments. Finally, six intermediates were identified by HPLC-MS/MS, and the degradation pathways were proposed. This study confirmed the feasibility of graphene coating on metals to achieve the enhancement of PMS activation. • The activation capacity of four types of normal-sized zero-valent copper catalyst on PMS was investigated. • The release of copper ions could be inhibited by graphene coating, while the degradation efficiencies of NPX increased. • PMS acted as an electron acceptor in the four copper-catalyzed PMS systems. • Hydroxyl radical was the dominant species in the degradation of NPX, and water acted as the radical precursor. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • UV/PDS is proposed to be unsuitable for treatment of bromophenols compared to UV/H 2 O 2. • Brominated polymeric products can be formed in UV-based oxidation process. • BrO 3 − evolution in the degradation of 2,4-DBP by UV/PDS exhibited biphasic kinetics. Abstract The sustained massive use of bromophenols in industrial products leads to their especially pernicious in aquatic environments. This study explored the oxidation kinetics of 2,4-bromophenol (2,4-DBP) and formation potential of bromate (BrO 3 −) and brominated polymeric products of concern during water treatment by UV/persulfate (PDS) and UV/hydrogen peroxide (H 2 O 2). 2,4-DBP exhibited appreciable reactivity toward sulfate radical (SO 4 −) and hydroxyl radical (HO). The second-order rate constants of SO 4 − and/or HO with 2,4-DBP at pH 9 were higher than those at pH 5 and 7. It is mainly due to the deprotonation of the hydroxyl group in 2,4-DBP when pH > pKa (pKa = 7.79). The chloride ions (Cl−) significantly inhibited 2,4-DBP degradation in UV/PDS process, which showed little inhibition in the UV/H 2 O 2 process. Carbonate/bicarbonate (CO 3 2−/HCO 3 −) and natural organic matters (NOM) significantly retarded 2,4-DBP degradation in both processes. BrO 3 − formation in UV/PDS process in the presence of 2,4-DBP (as organic carbon model compound) exhibited biphasic kinetics, i.e., BrO 3 − was undetectable in the lag phase and rapid generated in the secondary rapid phase. However, BrO 3 − was not detected throughout UV/H 2 O 2 process. According to the analysis by electrospray ionization-triple quadruple mass spectrometry, tentative oxidation pathway was proposed. The results showed that brominated polymeric products in the reaction of 2,4-DBP with SO 4 − and/or HO were readily produced by electrophilic addition and coupling reactions. Given the enhanced toxicological effects of these BrO 3 − and brominated polymeric products compared with the bromophenols precursors, it is important to better understand their reactivities and fates when UV/PDS or UV/H 2 O 2 is applied for the oxidative treatment of bromophenols-containing waters. [ABSTRACT FROM AUTHOR]

Abstract The frequent detection of propranolol, a widely used β-blocker, in wastewater effluents and surface waters has raised serious concern, due to its adverse effects on organisms. UV/hydrogen peroxide (UV/H 2 O 2) and UV/persulfate (UV/PDS) processes are efficient in eliminating propranolol in various waters, but the formation of oxidation products in these processes, as well as the assessment of their toxicity, has not been systematically addressed. In this study, we identified and compared transformation products of propranolol produced by hydroxyl radical (•OH) and sulfate radical (SO 4 •-). The electrostatic attraction enhances the reaction between SO 4 •- and the protonated form of propranolol, while •OH shows non-selectivity toward both protonated and neutral propranolol species. The hydroxylation of propranolol by •OH occurs at either amine moiety or naphthalene group while SO 4 •- favors the oxidation of the electron-rich naphthalene group. Further oxidation by •OH and SO 4 •- results in ring-opening products. Bicarbonate and chloride exert no effect on propranolol degradation. The generation of CO 3 •- and Cl-containing radicals is favorable to oxidizing naphthalene group. The acute toxicity assay of Vibrio fischeri suggests that SO 4 •- generates more toxic products than •OH, while CO 3 •- and Cl-containing radicals produce similar toxicity as SO 4 •-. High concentrations of bicarbonate in UV/H 2 O 2 increase the toxicity of treated solution. Graphical abstract Image 1 Highlights • Propranolol degradation is comparatively studied in UV/H 2 O 2 and UV/PDS. • CO 3.•- and Cl-containing radicals react with propranolol •.•OH induces hydroxylation of propranolol at either amine or naphthalene group • SO 4.•-, CO 3 •- and Cl-containing radicals attack the naphthalene group • SO 4.•-, CO 3 •- and Cl-containing radicals generate more toxic products than •OH [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The combination of O 3 with PMS had a strong enhancement on bromate formation. • The bromate formation process was clarified in O 3 /PMS process. • Bromate formation was the combined effect of molecular ozone, OH and SO 4 − in O 3 /PMS process. • The bromate formation was significantly inhibited in the actual water in O 3 /PMS process. Abstract Previously, we proposed a novel advanced oxidation process combining ozone (O 3) with peroxymonosulfate (PMS), which simultaneously produces sulfate radical (SO 4 −) and hydroxyl radical (OH) and significantly enhances the removal of organic matter. However, bromate formation is poorly understood during the oxidative treatment of bromide-containing water by O 3 /PMS process. In this study, factors influencing bromate formation were explored during the O 3 /PMS process, including the influences of solution pH, PMS dosage, and bromide concentration in distilled water and in actual water samples. Furthermore, the bromate formation mechanism was also clarified by monitoring the intermediate hypobromous acid (HOBr/OBr−), calculating the change of bromide species at different pH levels, and was further confirmed by adding radical scavengers. Generally, the O 3 /PMS process significantly promotes bromate formation compared with ozone treatment alone. During the O 3 /PMS process, increasing the PMS dosage and bromide concentrations promoted bromate formation, which was also significantly improved by raising the pH from 4.0 to 10.0. Bromate formation was a result of the combined effect of molecular ozone, OH, and SO 4 −, and the HOBr/OBr− was the essential intermediate species. Bromate formation was inhibited in the actual water sample due to the competitive effect of natural organic matter, bicarbonate, and reaction of HOBr/OBr− with ammonia. Therefore, the bromate formation should be evaluated as applying the O 3 /PMS process for organic matters abatement in bromide-containing actual water. [ABSTRACT FROM AUTHOR]

Abstract While fluoroquinolone (FQ) antibiotics are susceptible to degradation by sulfate and/or hydroxyl radicals formed in peroxymonosulfate (PMS) based advanced oxidation processes, here we report that unactivated PMS itself exhibits a specific high reactivity toward FQs for the first time. Reaction kinetics of PMS with two model FQs, ciprofloxacin (CF) and enrofloxacin (EF), showed a strong pH dependency with apparent second-order rate constants of 0.10–13.05 M−1s−1 for CF and 0.51–33.17 M−1s−1 for EF at pH 5–10. This pH dependency was well described by species-specific parallel reactions. On the basis of reaction kinetics and structure–activity assessment, the tertiary and secondary aliphatic N4 amines on the FQs' piperazine ring were proposed to be the main reaction sites. High performance liquid chromatography/electrospray ionization tandem mass analysis showed the formation of hydroxylated, N-oxide, and dealkylated products. Bacterial growth inhibition bioassays using Escherichia coli showed that oxidation products of FQs by PMS retained negligible antibacterial potency in comparison to parent FQs. Kinetic modeling using the rate constants estimated from pure water well predicted the oxidation kinetics of low levels of CF and EF by PMS in surface water. The degradation efficiency of FQs by PMS in surface water was slightly lower than that by ozone, comparable to that by ferrate, and much higher than that by permanganate. These results suggest that PMS is a promising oxidant for the treatment of FQs in water. Graphical abstract Image 1 Highlights • Direct oxidation of FQs by PMS without activation showed strong pH dependency. • Aliphatic N4 amines on the FQs' piperazine ring were the main reaction sites. • Transformation of FQs yielded hydroxylated, N-oxide, and dealkylated products. • Oxidation products had a much lower antibacterial activity than parent FQs. • FQs were efficiently degraded by PMS in natural water. [ABSTRACT FROM AUTHOR]

• The addition of PI greatly promoted the degradation of organic pollutants by In 2 O 3 /Vis-LED process. • • OH was formed through the reaction of holes with H 2 O and played a major role. • PI received electrons from the conduction band of the In 2 O 3 and eventually changed to iodate. • The species variation of PI with pH did not affect its ability to accept electrons. Periodate (PI) as an oxidant has been extensively studied for organic foulants removal in advanced oxidation processes. Here PI was introduced into In 2 O 3 /Vis-LED process to enhance the formation of ·OH for promoting the degradation of organic foulants. Results showed that the addition of PI would significantly promote the removal of sulfamethoxazole (SMX) in the In 2 O 3 /Vis-LED process (from 9.26% to 100%), and ·OH was proved to be the dominant species in the system. Besides, the process exhibited non-selectivity in the removal of different organic foulants. Comparatively, various oxidants (e.g., peroxymonosulfate, peroxydisulfate, and hydrogen peroxide) did not markedly promote the removal of SMX in the In 2 O 3 /Vis-LED process. Electrochemical analyses demonstrated that PI could effectively receive photoelectrons, thus inhibiting the recombination of photogenerated electron-hole (e −/ h +) pairs. The holes then oxidized the adsorbed H 2 O to generate ·OH, and the PI converted to iodate at the same time. Additionally, the removal rate of SMX reduced from 100% to 17.2% as Vis-LED wavelengths increased from 440 to 560 nm, because of the low energy of photons produced at longer wavelengths. Notably, the species of PI do not affect its ability to accept electrons, resulting in the degradation efficiency of SMX irrespective of pH (4.0–10.0). The coexistence of inorganic cations and anions (such as Cl−, CO 3 2−/HCO 3 −, SO 4 2−, Ca2+, and Mg2+) also had an insignificant effect on SMX degradation. Furthermore, the process also showed excellent degradation potential in real water. The proposed strategy provides a new insight for visible light-catalyzed activation of PI and guidance to explore green catalytic processes for high-efficiency removal of various organic foulants. [Display omitted] [ABSTRACT FROM AUTHOR]

• The irradiation of Cr(VI) by solar light effectively degraded various micropollutants. • OH was the major reactive species contributing to micropollutant degradation in the solar light/Cr(VI) system. • Cr(V) was determined as the important intermediate of •OH formation. • The natural solar light/Cr(VI) system showed great potential for micropollutant degradation. Hexavalent chromium (Cr(VI)) is ubiquitous in natural environments, whereas its role in the transformation of coexisting contaminants may have been overlooked. In this work, it was reported for the first time that the irradiation of Cr(VI) by solar light (solar light/Cr(VI) system) could effectively degrade various micropollutants with different structures. The removal efficiency of selected micropollutants was increased by 13.3–64.8% by the solar light/Cr(VI) system compared to that by direct solar photolysis. Meanwhile, the oxidation rates were enhanced by 2.2–21.5 folds, while they were negligible by Cr(VI) oxidation alone. Experiments by specific scavengers, probe compounds, fluorescence absorbance, and electron spin resonance analysis demonstrated that hydroxyl radical (•OH) was the major reactive species in the solar light/Cr(VI) system. Further experiments showed that the generation of •OH was closely related to the intermediate Cr(V) generated from Cr(VI) reduction, and Cr(V) could be re-oxidized back to Cr(VI). Increasing solution pH negatively affected model micropollutant (carbamazepine (CBZ)) degradation by the solar light/Cr(VI) system, mainly due to the decreased quantum yield of •OH at higher pH. Coexisting sulfate ions showed negligible effect on CBZ degradation in the solar light/Cr(VI) system, while the presence of bicarbonate, chloride, and humic acid inhibited CBZ degradation to varying degrees, owing to their diverse scavenging effects on •OH. Furthermore, moderate CBZ degradation was also achieved by natural solar light photolysis of Cr(VI). This study demonstrated the pivotal role of Cr(VI) in the transformation of micropollutants under solar irradiation, which advances the understanding of the fate of micropollutants in natural environments. [Display omitted] [ABSTRACT FROM AUTHOR]

• Fe(II)/PAA efficiently oxidized p -ASA at pH ≤ 7.0 with the optimum [Fe(II)] to [PAA] ratio of 2:1. • •OH and CH 3 C(O)O• contributed to p -ASA degradation by the Fe(II)/PAA process. • 2 organic and 4 inorganic products were detected during PAA oxidation by the Fe(II)/PAA process. • PAA rapidly oxidized As(III) to As(V) at pH ≥ 7.0 with a stoichiometry of [As(III)] to [PAA] of 1:1. • Total arsenic was effectively removed by ferric precipitates in both synthetic and real waters. The widespread occurrence of p -arsanilic acid (p -ASA) in natural environments poses big threats to the biosphere due to the generation of toxic inorganic arsenic (i.e., As(III) and As(V), especially As(III) with higher toxicity and mobility). Oxidation of p -ASA or As(III) to As(V) followed by precipitation of total arsenic using Fe-based advanced oxidation processes demonstrated to be a promising approach for the treatment of arsenic contamination. This study for the first time investigated the efficiency and inherent mechanism of p -ASA and As(III) oxidation by Fe(II)/peracetic acid (Fe(II)/PAA) and PAA processes. p -ASA was rapidly degraded by the Fe(II)/PAA process within 20 s at neutral to acidic pHs under different conditions, while it was insignificantly degraded by PAA oxidation alone. Lines of evidence suggested that hydroxyl radicals and organic radicals generated from the homolytic O O bond cleavage of PAA contributed to the degradation of p -ASA in the Fe(II)/PAA process. p -ASA was mainly oxidized to As (V), NH 4 +, and p -aminophenol by the Fe(II)/PAA process, wherein the aniline group and its para position were the most vulnerable sites. As(III) of concern was likely generated as an intermediate during p -ASA oxidation and it could be readily oxidized to As(V) by the Fe(II)/PAA process as well as PAA alone. The in-depth investigation demonstrated that PAA alone was effective in the oxidation of As(III) under varied conditions with a stoichiometric molar ratio of 1:1. Efficient removal (> 80%) of total arsenic during p -ASA oxidation by Fe(II)/PAA process or during As(III) oxidation by PAA process with additional Fe(III) in synthetic or real waters were observed, mainly due to the adsorptive interactions of amorphous ferric (oxy)hydroxide precipitates. This study systematically investigates the oxidation of p -ASA and As(III) by the Fe(II)/PAA and PAA processes, which is instructive for the future development of arsenic remediation technology. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesized nitrogen-doped rGO (N-rGO) was firstly applied to activate sulfite. • Polarized carbon atom adjacent to the doped nitrogen primarily induced activation. • The generated HO• was mainly responsible for the oxidation of As(III) to As(V). • N-rGO with more pyridine nitrogen has higher catalytic activity. As a metal-free alternative, graphene-based catalysts have attracted increasing attention for minimizing the risk of heavy metal exposure. In this study, a nitrogen–doped reduced graphene oxide (N-rGO) material was synthesized by a one–pot hydrothermal method using dicyandiamide as the precursor. N-rGO has been adopted for sulfite activation for the first time, to our knowledge. The established N–rGO/sulfite system could effectively remove As(III) in water, and the solution pH and dissolved oxygen were the most important factors affecting the removal. The results of density functional theory calculations indicated that sulfite activation was more likely to occur on C atoms adjacent to the N dopant. It was inferred that the generated hydroxyl radical (HO•) played a vital role in As(III) oxidation. In addition, the conversion of pyridinic nitrogen to pyrrolic nitrogen was responsible for the poor long–term stability of N-rGO. These results demonstrated that N-rGO was a promising catalyst for water treatment. [ABSTRACT FROM AUTHOR]

Vacuum-Ultraviolet (VUV), an efficient and green method to produce hydroxyl radical (•OH), is effective in degrading numerous organic contaminants in aqueous solution. Here, we proposed an effective and simple kinetic model to describe the degradation of organic pollutants in VUV system, by taking the •OH scavenging effects of formed organic intermediates as co-existing organic matter in whole. Using benzoic acid (BA) as a •OH probe, •OH was regarded vital for pollutant degradation in VUV system, and the thus developed model successfully predicted its degradation kinetics under different conditions. Effects of typical influencing factors such as BA concentrations and UV intensity were investigated quantitatively by the model. Temperature was found to be an important influencing factor in the VUV system, and the quantum yield of •OH showed a positive linear dependence on temperature. Impacts of humic acid (HA), alkalinity, chloride, and water matrices (realistic waters) on the oxidation efficiency were also examined. BA degradation was significantly inhibited by HA due to its scavenging of •OH, but was influenced much less by the alkalinity and chloride; high oxidation efficiency was still obtained in the realistic water. The degradation kinetics of three other typical micropollutants including bisphenol A (BPA), nitrobenzene (NB) and dimethyl phthalate (DMP), and the mixture of co-existing BA, BPA and DMP were further studied, and the developed model predicted the experimental data well, especially in realistic water. It is expected that this study will provide an effective approach to predict the degradation of organic micropollutants by the promising VUV system, and broaden the application of VUV system in water treatment. [ABSTRACT FROM AUTHOR]

Studying the ecological risks of antibiotics and their degradation products is of great importance to water environment security and advanced oxidation processes (AOPs) development. This work studied the changes and internal influencing mechanisms of ecotoxicity and the capacity for inducing antibiotic resistance genes (ARGs) shown by the tetracycline (TC) degradation products generated in AOPs with differential free radicals. Under the action of superoxide radicals and singlet oxygen in the ozone system, and sulfate and hydroxyl radicals in the thermally activated potassium persulfate system, TC exhibited differential degradation pathways and resulted in the differential growth inhibition trends on the determined strains. Microcosm experiments combined with metagenomics were also performed to analyze the remarkable changes in the TC resistance genes tetA (60), tetT , and otr (B) induced by the degradation products and ARG hosts in the natural water environment. Microcosm experiments exhibited that the microbial community in actual water have changed significantly with the addition of TC and degradation intermediates. Furthermore, the richness of genes related to oxidative stress was investigated to discuss the effect on reactive oxygen species production and SOS response caused by TC and its intermediates. • ARGs induction testing and hosts analysis usingmicrocosm experiment combined with metagenomic methods. • Tetracycline was degraded by active oxidizing species domination. • The ecological risks of tetracycline intermediates changed with the different degradation mechanisms. [ABSTRACT FROM AUTHOR]