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1.
Chem Commun (Camb) ; 55(86): 12956-12959, 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31602444

RESUMO

A bimetallic complex, containing Mn(ii) and Cu(ii) moieties, was synthesized for chemodynamic therapy (CDT) of cancer. The complex was capable of generating a hydroxyl radical (˙OH) via a Fenton-like reaction involving a Mn complex, and simultaneously depleting glutathione via a Cu complex induced oxidative reaction, thereby enhancing the efficiency of CDT.


Assuntos
Complexos de Coordenação/química , Cobre/química , Glutationa/metabolismo , Manganês/química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Complexos de Coordenação/farmacologia , Complexos de Coordenação/uso terapêutico , Glutationa/química , Humanos , Radical Hidroxila/metabolismo , Azul de Metileno/química , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Fotoquimioterapia
2.
Chemosphere ; 235: 1180-1188, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561309

RESUMO

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a class of highly persistent contaminants with high bioaccumulation and toxicity. Our previous studies showed that perfluorooctanoic acid (PFOA) can be completely defluorinated under UV irradiation in organo-montmorillonite/indole acetic acid (IAA) system. However, there is still lack of information for the degradation mechanism and the test for wastewater treatment. Here, we systematically investigated the defluorination reaction in the presence of different organo-montmorillonites and found that the degradation process was apparently controlled by the configuration of surfactants. In hexadecyltrimethyl ammonium (HDTMA)-modified montmorillonite, HDTMA exists as a tilt conformation and isolated clay interlayer from the aqueous solution, protecting hydrated electrons generated by photo-irradiation of IAA from quenching by oxygen. Defluorination hydrogenation process was the dominant degradation pathway. While in poly-4-vinylpyridine-co-styrene (PVPcoS)-modified montmorillonite, due to the multiple charges of PVPcoS, a flat conformation parallel to clay surface was expected. Hydroxyl radicals, which were generated by the reaction of hydrated electrons with oxygen molecules diffused into clay interlayer, are also involved in the degradation process. Our results further demonstrate that mixture modified montmorillonite could combine the advantages of both modifications, thus showing superior reactivity even for actual industrial wastewater without any pretreatment. This technique would have great potential for treatment of actual wastewater.


Assuntos
Bentonita/química , Caprilatos/química , Argila/química , Elétrons , Fluorcarbonetos/química , Tensoativos/química , Adsorção , Radical Hidroxila/química , Conformação Molecular , Purificação da Água/métodos
3.
Water Res ; 166: 115083, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31541794

RESUMO

Hydroxyl radicals (·OH) initiated degradation is an important process governing fate of aquatic organic micropollutants (OMPs). However, rate constants for aqueous reaction of OMPs with ·OH (kOH) are available only for a limited number of OMPs, which complicates fate assessment of OMPs. Furthermore, molecular structures of many OMPs contain ionizable groups, and the OMPs may dissociate into different anionic/cationic species with different reactivity towards ·OH. Therefore, it is of importance to determine kOH of ionizable OMPs, and to develop quantitative structure-activity relationship (QSAR) models for predicting kOH of OMPs at different ionization forms. Herein kOH values of 9 fluoroquinolones (FQs) and 11 sulfonamides (SAs) at 3 dissociation forms (FQ±/FQ+/FQ-, SA0/SA+/SA-) were determined by competition kinetics experiments. A QSAR model using theoretical molecular structural descriptors was subsequently developed. The QSAR model successfully corroborated previous experimental results, exhibited good statistical performance, and is capable to predict kOH for FQs and SAs with different dissociation forms at environmentally relevant pH conditions. As organic ions have rarely been included in previous QSAR studies, the newly developed model that covers both neutral molecules and ions is of significance for future QSAR development as well as fate assessment of ionizable OMPs.


Assuntos
Radical Hidroxila , Poluentes Químicos da Água , Fluoroquinolonas , Relação Quantitativa Estrutura-Atividade , Sulfonamidas
4.
Chemosphere ; 235: 1007-1014, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561289

RESUMO

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.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Eletrodos , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Oxidantes/química , Ozônio/química , Poluentes Químicos da Água/química , Compostos Azo/análise , Benzenossulfonatos/análise , Eletrólise , Oxirredução , Poluentes Químicos da Água/análise
5.
Environ Pollut ; 252(Pt B): 1863-1871, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31369942

RESUMO

Alternative transportation fuels (ATFs) can reduce air pollution. However, the influence of conventional fuels-diesel and gasoline, and particularly ATFs on photochemical air pollution is not well-characterized, limiting assessments of ATFs and air quality. This is mainly due to frequent use of lumped chemical mechanisms by related atmospheric modeling. Here we hypothesized that applying a chemical mechanism that is specifically developed according to both emission fractions and photochemical ozone creation potential of volatile organic compounds (VOCs) is key to gaining reliable insights into the impact of transportation fuels on photochemistry. We used a heterogeneous chemical mechanism with 927 reactions and relatively detailed emission inventories to specifically meet the requirements for reliable simulation of the effect of exhaust emissions from vehicles fueled by selected model fuels-diesel, gasoline, and mixtures of 15% gasoline with 85% ethanol (E85) or 85% methanol (M85)-on photochemistry. These dispersion-box model simulations revealed a strong influence of atmospheric background balance between VOCs and nitrogen oxides (NOX = [NO] + [NO2]) on the impact of exhaust emissions on photochemistry, with higher tendency toward ozone (O3) formation or destruction for more VOC-limited or NOX-limited conditions, respectively. Accordingly, higher [NOX]/[VOC] exhaust emission, such as from diesel and M85, resulted in lower O3, not only locally but also downwind of the emission. This offers a new perspective and measure for transportation fuel assessment. Rapid conversion of O3 to hydroxyl and hydroperoxyl radicals downwind of the exhaust emission indicates the importance of simulating the impact of road transportation on photochemistry at high spatial and temporal resolution. Peroxyacetyl nitrate formation was more sensitive to VOC emission under VOC-limited conditions than to NOX emission under NOX-limited conditions. Secondary formaldehyde dominated over primary emitted formaldehyde several minutes after emission. These findings should be verified using a 3D modeling study under varying meteorological conditions.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , Gasolina/análise , Óxidos de Nitrogênio/análise , Ozônio/análise , Emissões de Veículos/análise , Radical Hidroxila/análise , Modelos Teóricos , Fotoquímica , Transportes , Compostos Orgânicos Voláteis/análise
6.
Water Res ; 163: 114894, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31374404

RESUMO

This work presents a kinetic analysis of the exogenous photo-induced disinfection of E. coli in natural waters. Herein, the inactivation of bacteria by light and photo-generated transient species, i.e., hydroxyl radical (HO•), excited triplet states of organic matter (3CDOM*) and singlet oxygen (1O2), was studied. It was found that the exogenous disinfection of E. coli proceeds through a lag time, followed by an exponential phase triggered by photo-generated HO•, 1O2 and 3CDOM*. Also, we report that the concentration increased of transient species (and especially HO•) precursors decreased the lag times of bacteria inactivation. Due to the limitations of the competition kinetics methodology to include the lag phase, an alternative strategy to study the interaction between E. coli and photo-generated transient species was proposed, considering the log-linear pseudo-first order rate constants and lag-times. On this basis and by using APEX software, a full kinetic analysis of exogenous bacterial inactivation, taking into account both lag-time and exponential decay, was developed. This approach provided insights into the conditions that could make exogenous inactivation competitive with the endogenous process for the E. coli inactivation in natural sunlit waters. Hence, this research contributes to the understanding of fundamental kinetic aspects of photoinduced bacterial inactivation, which is the basis for light-assisted processes such as the solar disinfection (SODIS).


Assuntos
Desinfecção , Escherichia coli , Radical Hidroxila , Cinética , Oxigênio Singlete
7.
Ecotoxicol Environ Saf ; 183: 109551, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31419701

RESUMO

Sulfate radical (SO4-) and hydroxyl radical (OH) generated from persulfate or peroxymonosulfate in AOPs have been widely used in contaminant degradation. Anthracene (ANT) can be decomposed by SO4- and OH. The processes of ANT decomposition were investigated using theoretical calculations in this paper. The initiation reactions of ANT, anthrone, anthraquinone (ATQ) and 1-hydroxylanthraquinone (1-hATQ) by two radicals are studied. The highest free energy barriers of initiation reactions are 22.30 kcal mol-1 in ATQ + SO4- reaction and 6.84 kcal mol-1 in ATQ + OH reaction. Comparing the rate constants of initiation reaction through the two radicals at 273-373 K, it can be concluded that SO4- and OH both play important roles on the initiation of ANT and anthrone at lower pH. For ATQ and 1-hATQ, OH is more important than SO4- in the initiation process, which indicates that the indirect influence of SO4- are more significant in the degradation processes of ATQ and 1-hATQ. This study provides theoretical confirmations for the mechanisms of reactions of ANT with SO4- and OH, and evaluates the importance of SO4- and OH according to the reaction rates. The work can give more insight into the degradation of PAHs by radicals.


Assuntos
Antracenos/química , Radical Hidroxila/química , Modelos Teóricos , Sulfatos/química , Poluentes Químicos da Água/química , Cinética , Oxirredução , Teoria Quântica , Soluções , Purificação da Água
8.
Environ Pollut ; 254(Pt A): 113040, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31421579

RESUMO

Triphenyl phosphate (TPHP) is one of the major organophosphate esters (OPEs) with increasing consumption. Considering its largely distribution and high toxicity in aquatic environment, it is important to explore an efficient treatment for TPHP. This study aimed to investigate the accelerated degradation of TPHP in a three-electrode single chamber bioelectrochemical system (BES). Significant increase of degradation efficiency of TPHP in the BES was observed compared with open circuit and abiotic controls. The one-order degradation rates of TPHP (1.5 mg L-1) were increased with elevating sodium acetate concentrations and showed the highest value (0.054 ±â€¯0.010 h-1) in 1.0 g L-1 of sodium acetate. This result indicated bacterial metabolism of TPHP was enhanced by the application of micro-electrical field and addition acetate as co-substrates. TPHP could be degraded into diphenyl phosphate (DPHP), hydroxyl triphenyl phosphate (OH-TPHP) and three byproducts. DPHP was the most accumulated degradation product in BES, which accounted more than 35.5% of the initial TPHP. The composition of bacterial community in BES electrode was affected by the acclimation by TPHP, with the most dominant bacteria of Azospirillum, Petrimonas, Pseudomonas and Geobacter at the genera level. Moreover, it was found that the acute toxic effect of TPHP to Vibrio fischeri was largely removed after the treatment, which revealed that BES is a promising technology to remove TPHP threaten in aquatic environment.


Assuntos
Retardadores de Chama , Modelos Químicos , Organofosfatos/química , Radical Hidroxila , Cinética , Organofosfatos/metabolismo , Fosfatos
9.
Water Sci Technol ; 80(1): 25-36, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31461419

RESUMO

The ozonation efficiency for removal of recalcitrant organic pollutants in alkaline wastewater is always low because of the presence of some hydroxyl radical scavengers. To solve this problem, the O3/Ca(OH)2 system was put forward, and p-nitrophenol (PNP) was chosen to explore the mechanism of this system. The effects of key operational parameters were studied respectively; the Ca(OH)2 dosage 3 g/L, ozone inlet flow rate 3.5 L/min, ozone concentration 65 mg/L, reactor pressure 0.25 MPa, and temperature 25 °C were obtained as the optimal operating conditions. After 60 min treatment, the organic matter mineralized completely, which was higher than the sum of the ozonation-alone process (55.63%) and the Ca(OH)2 process (3.53%). It suggests that the calcium hydroxide in the O3/Ca(OH)2 process possessed a paramount role in the removal of PNP. The liquid samples and the precipitated substances were analyzed by gas chromatography mass spectrometry, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy; it was demonstrated that Ca(OH)2 could accelerate the generation of hydroxyl radical and simultaneously in situ separate partial intermediate products and CO32- ions through some precipitation reactions.


Assuntos
Microbolhas , Nitrofenóis/química , Ozônio , Poluentes Químicos da Água/química , Radical Hidroxila , Eliminação de Resíduos Líquidos
10.
Analyst ; 144(17): 5284-5291, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31372627

RESUMO

5,10,15,20-Tetrakis(4-carboxyl phenyl)porphyrin (Por) modified Co(OH)2 deposited on the surface of GO nanocomposites (Por/Co(OH)2/GO) were prepared and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and XRD. For the first time, H2TCPP/Co(OH)2/GO is found to have enhanced peroxidase-like activity and catalyze the oxidation of the substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2). Notably, the colorless TMB rapidly transformed into blue oxTMB in just 60 s, which was easily observed visually. The catalytic kinetics of H2TCPP/Co(OH)2/GO is in accord with the Michaelis-Menten equation. The catalytic mechanism of H2TCPP/Co(OH)2/GO nanocomposites is attributed to hydroxyl radicals (˙OH), due to decomposition of H2O2, which is verified by using terephthalic acid as a fluorescent probe. What's more, H2O2 can be detected in a wide linear detection range from 5 to 35 mM with a detection limit of 0.385 mM. Furthermore, based on the excellent peroxidase-like activity of H2TCPP/Co(OH)2/GO, a colorimetric sensor is established to sensitively detect glutathione (GSH) in a linear range from 10 to 300 µM with a low detection limit of 9.5 µM.


Assuntos
Cobalto/química , Grafite/química , Hidróxidos/química , Nanocompostos/química , Peroxidases/química , Porfirinas/química , Benzidinas/química , Materiais Biomiméticos , Técnicas Biossensoriais/métodos , Catálise , Glutationa/análise , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Limite de Detecção , Oxirredução , Sensibilidade e Especificidade , Propriedades de Superfície
11.
Phytochemistry ; 166: 112077, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31374519

RESUMO

Radical scavenging activity and subsequent oxidation resulting in quinone products represent one of the important features of phenols occurring in plants and other biological systems. However, corresponding thermochemistry data can be still considered scarce. For phenol and 25 para-substituted phenols, we investigate the thermodynamics of the individual reaction steps, including three subsequent hydrogen atom transfers, as well as hydroxyl HO radical addition, leading to final ortho-quinone formation. The substituent and solvent effect of water on corresponding reactions enthalpies is elucidated. Solvent enhances substituent induced changes in the investigated reaction enthalpies. The reliability of employed computational methods for the thermodynamics of hydrogen atom donating ability of studied phenols and catechols is assessed, too. Obtained linear equations enable estimation of studied reaction enthalpies from Hammett constants of substituents.


Assuntos
Depuradores de Radicais Livres/química , Fenóis/química , Quinonas/química , Radical Hidroxila/química , Isomerismo , Relação Estrutura-Atividade , Termodinâmica
12.
J Agric Food Chem ; 67(28): 7961-7967, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31260294

RESUMO

Food-derived glycated phospholipids is potentially hazardous to human health. However, there are few studies on the effects of lipids on the formation of glycated phospholipids. In this work, two model systems were established: (1) a model system including 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (PE), glucose, and Fenton reagent and (2) a model system including PE, glucose, and five kind of vegetable oils. The contents of carboxymethyl-PE, carboxyethyl-PE, Amadori-PE, hydroxyl radical (OH•), glyoxal, and methylglyoxal were determined with high-performance liquid chromatography mass spectrometry. The results of the first model system showed that OH• oxidized glucose to produce glyoxal and methylglyoxal, which then reacted with PE to form carboxymethyl-PE and carboxyethyl-PE. OH• also oxidized Amadori-PE to form carboxymethyl-PE. The results of the second model system showed that vegetable oils with higher number of moles of carbon-carbon unsaturated double bond in vegetable oil per kilogram could produce more OH•, which promote the formation of carboxymethyl-PE and carboxyethyl-PE by oxidizing glucose and oil. We elucidated the effects of oils on the formation of glycated phospholipids in terms of OH• and intermediates. This work will contribute to better understanding the formation mechanism of glycated phospholipids with oil.


Assuntos
Radical Hidroxila/química , Lipídeos/química , Fosfolipídeos/química , Cromatografia Líquida de Alta Pressão , Glucose/química , Glicosilação , Glioxal/química , Reação de Maillard , Espectrometria de Massas , Modelos Químicos , Oxirredução , Aldeído Pirúvico/química
13.
Environ Sci Process Impacts ; 21(8): 1393-1402, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31322150

RESUMO

The hydroxyl radical (OH) is one of the most important oxidants controlling the oxidation capacity of the indoor atmosphere. One of the main OH sources indoors is the photolysis of nitrous acid (HONO). In this study, real-time measurements of HONO, nitrogen oxides (NOx) and ozone (O3) in an indoor environment in Guangzhou, China, were performed under two different conditions: (1) in the absence of any human activity and (2) in the presence of cooking. The maximum NOx and HONO levels drastically increased from 15 and 4 ppb in the absence of human activity to 135 and 40 ppb during the cooking event, respectively. The photon flux was determined for the sunlit room, which has a closed south-east oriented window. The photon flux was used to estimate the photolysis rate constants of NO2, J(NO2), and HONO, J(HONO), which span the range between 8 × 10-5 and 1.5 × 10-5 s-1 in the morning from 9:30 to 11:45, and 8.5 × 10-4 and 1.5 × 10-4 s-1 at noon, respectively. The OH concentrations calculated by photostationary state (PSS) approach, observed around noon, are very similar, i.e., 2.4 × 106 and 3.1 × 106 cm-3 in the absence of human activity and during cooking, respectively. These results suggest that under "high NOx" conditions (NOx higher than a few ppb) and with direct sunlight in the room, the NOx and HONO chemistry would be similar, independent of the geographic location of the indoor environment, which facilitates future modeling studies focused on indoor gas phase oxidation capacity.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Radical Hidroxila/análise , Óxidos de Nitrogênio/análise , Ácido Nitroso/análise , Ozônio/análise , Fotólise , China , Culinária , Humanos , Modelos Teóricos , Ácido Nitroso/efeitos da radiação , Oxirredução , Ozônio/efeitos da radiação , Luz Solar
14.
Environ Sci Pollut Res Int ; 26(25): 26134-26145, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31280443

RESUMO

Nitrous acid (HONO) is an important atmospheric pollutant that can strongly absorb ultraviolet irradiation in the region of 300-400 nm, as previously reported. Since the solar irradiance that reaches the surface of the earth has wavelengths greater than 290 nm, the photodissociation of HONO is considered the major method of hydroxyl radical formation in the troposphere. Thus, the photoinduced chemical reactivity of HONO is important. The present work investigated the reaction mechanism and kinetic parameters of HONO and sulfamethazine by using a laser flash photolysis technique and liquid chromatography-mass spectrometry. The results indicated that the sulfamethazine degradation rate was influenced by the HONO concentration and the initial concentration of sulfamethazine. Hydroxyl radicals derived from the photolysis of HONO attacked the aromatic ring of sulfamethazine to form sulfamethazine-OH adducts with a second-order rate constant of (3.8 ± 0.3) × 109 L mol-1 s-1. This intermediate would then react with HO· and oxygen molecules. The reaction rate constants of sulfamethazine-OH adducts with oxygen are (1.3 ± 0.1) × 107 L mol-1 s-1. The generation of sulfanilic acid and pyrimidine implies that the breaking down of S-N bonds of sulfamethazine and its HO adducts probably occur at the same time.


Assuntos
Radical Hidroxila/química , Ácido Nitroso/química , Oxigênio/química , Sulfametazina/química , Cinética , Fotólise , Raios Ultravioleta , Água/química
15.
Food Chem ; 299: 125095, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31279124

RESUMO

Hydrogen gas (H2), a multifunctional signaling molecule, has received increasing attention in recent years. In the present study, hydrogen-rich water (HRW) (2 ppm) was used for the processing of sprouted black barley (Hordeum distichum L.), and the results showed that the HRW treatment could significantly increase the germination rate and growth rate of black barley (P < 0.05). A chemical component analysis showed that in sprouted black barley, the HRW treatment could change the distribution of phytochemicals (e.g., the ionic strength of guanosine), increase the concentrations of free vanillic acid, coumaric acid, sinapic acid, conjugated sinapic acid, Ca and Fe and the hydroxyl radical scavenging rate, and decrease the protein, fat, starch and dietary fibre contents compared with the results obtained after treatment with ultra-pure water (P < 0.05). HRW can be used for the processing of sprouted grains to effectively increase their germination efficiency and concentrations of bioactive phytochemicals.


Assuntos
Hordeum/química , Hordeum/crescimento & desenvolvimento , Hidrogênio/farmacologia , Antioxidantes/análise , Cromatografia Líquida , Fibras na Dieta/análise , Germinação/efeitos dos fármacos , Hordeum/efeitos dos fármacos , Radical Hidroxila/análise , Espectrometria de Massas , Proteínas de Vegetais Comestíveis/análise , Amido/análise , Água/química , Água/farmacologia
16.
Chemosphere ; 235: 143-152, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31255754

RESUMO

Ni-Fe Layered Double Hydroxides (Ni-Fe LDHs) was prepared, characterized and used as catalyst in heterogeneous catalytic ozonation of Bisphenol A (BPA) and other organic compounds in secondary effluent. The characterization and ozonation results revealed that the Ni-Fe LDHs possessing a Ni: Fe ratio of 3:1 had the best crystalline and the highest affinity for ozone. Under the optimized conditions, the final TOC and COD removal achieved was 56% and 68%, respectively. BPA in the secondary effluent could be removed completely by Ni3-Fe LDH catalyzed ozonation. The organic compounds removal was mainly attributed to the oxidation by free active radicals such as hydroxyl radicals (OH). In this research the accumulative ·OH in the reaction system was determined to be 28.2 µmol at the reaction time of 60 min. The free active radicals were mostly generated through the electron transfer among different valences of metals on Ni-Fe LDHs surface, and subsequently diffused into bulk solution to oxidize the target organic compounds there.


Assuntos
Compostos Benzidrílicos/análise , Ferro/química , Níquel/química , Fenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Hidróxidos/química , Radical Hidroxila/química , Oxirredução , Ozônio/química
17.
Chemosphere ; 235: 575-585, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31276870

RESUMO

This study investigated the abatement of a number of antimicrobials frequently detected in municipal wastewater by conventional ozonation and a recently developed ozone-based advanced oxidation process, the electro-peroxone (E-peroxone) process. A synthetic water and a real secondary wastewater effluent were spiked with fourteen antimicrobials, including antibiotics and biocides, and then treated by the two processes. The results show that most of the antibiotics investigated (e.g., ofloxacin, trimethoprim, norfloxacin, and ciprofloxacin) readily react with ozone (O3) and could therefore be efficiently eliminated from the water matrices by direct O3 oxidation during both processes. In contrast, most of the biocides tested in this study (e.g., clotrimazole, pentamidine, bixafen, propiconazole, and fluconazole) were only moderately reactive, or non-reactive, with O3. Therefore, these biocides were removed at considerably lower rate than the antibiotics during the two ozone-based processes, with hydroxyl radical (OH) oxidation playing an important role in their abatement mechanisms. When compared with conventional ozonation, the E-peroxone process is defined by the in situ electrogeneration of hydrogen peroxide, which considerably enhances the transformation of O3 to OH. As a result, the E-peroxone process significantly accelerated the abatement of biocides and required a considerably shorter treatment time to eliminate all of the tested compounds from the water matrices than conventional ozonation. In addition, the E-peroxone process enhanced the contributions of OH fractions to the abatement of moderately ozone reactive benzotriazoles. These results demonstrate that the E-peroxone process holds promise as an effective tertiary treatment option for enhancing the abatement of ozone-resistant antimicrobials in wastewater.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Antibacterianos , Desinfetantes , Peróxido de Hidrogênio , Radical Hidroxila , Oxirredução , Ozônio , Água , Poluentes Químicos da Água/análise , Purificação da Água/métodos
18.
Chemosphere ; 235: 749-756, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31280043

RESUMO

In this study, the copper nanoparticles (Cu NPs) reactivity for degradation of the reactive dye black 5 (RP5), picric acid (PA) and 2,4-D herbicide was evaluated. The RP5 degradation occurred by oxidative via, through hydroxyl radicals generated in situ, with active participation of Cu(I) and H2O2. The use of catalase confirmed the hydrogen peroxide formation in situ. Reduction degradation via electron transfer was also possible. On the other hand, PA had low degradation efficiency (less than 20%) under any conditions studied (similar to those used for RP5). High degradation efficiency for 2,4-D was achieved by the association of the Cu NPs/H2O2. Thus, the behavioral model of Cu NPs has been proven. This behavioral difference of the chemical species to be degraded in relation to the behavior of the Cu NPs was studied, evaluating its redox behavior by voltammetric analyzes. This study aided in the understanding and selection of the chemical species that can be degraded by these NPs.


Assuntos
Ácido 2,4-Diclorofenoxiacético/química , Cobre/química , Nanopartículas/química , Naftalenossulfonatos/química , Picratos/química , Catalase/metabolismo , Herbicidas/química , Peróxido de Hidrogênio/química , Radical Hidroxila , Oxirredução
19.
Environ Sci Pollut Res Int ; 26(26): 27482-27493, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31332683

RESUMO

Sunflower stalk-derived biochars (BC) were prepared at various temperatures (i.e., 500, 650, and 1000 °C) and demonstrated as a highly efficient catalyst in persulfate (PS) activation for the oxidation of p-nitrophenol (PNP) at 60 °C. The apparent PNP oxidation rate constant in the BC500 (0.1543 L mol-1 S-1), BC650 (0.6062 L mol-1 S-1), or BC1000 (2.1379 L mol-1 S-1) containing PS system was about 2, 8 and 28 times higher than that in PS/PNP (0.0751 L mol-1 S-1) system, respectively. The effect of reaction temperature on PNP oxidation was also investigated. Furthermore, the radical quenching tests and electron paramagnetic resonance spectroscopy (EPR) were employed to investigate the sulfate and hydroxyl radicals for PNP oxidation. The Raman results suggested that the defective sites on biochars possess vital role for oxidation of PNP in PS system. The possible activation pathway of PS/BC was proposed that the defective sites on BC were involved for weakening the O-O bond in PS and subsequently cleaving O-O bond by heat to generate sulfate radical. The oxidation of PNP at low concentration (below 100 µg L-1) was completely removed in urban wastewater by PS/BC system within 30 min. This work would provide new insights into PS activation by BC catalyst and afford a promising method for organic pollutant removal in high-temperature wastewater.


Assuntos
Carvão Vegetal/química , Helianthus/química , Nitrofenóis/química , Poluentes Químicos da Água/química , Catálise , Espectroscopia de Ressonância de Spin Eletrônica , Radical Hidroxila/química , Oxirredução , Caules de Planta/química , Sulfatos/química , Temperatura Ambiente , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química
20.
Chemosphere ; 235: 260-270, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31260866

RESUMO

Micropollutants such as pharmaceutical products and pesticides are still present in treated wastewater. Several of these compounds are photoactive, either by direct or indirect photodegradation. An innovative on-site experimental protocol was designed to investigate the contribution of photodegradation processes to eliminate micropolluants in constructed wetland (CW). The solar photodegradation of 23 organic micropollutants was studied using in situ photoreactors at different depths. A CW-photodegradation model was designed and calibrated to further scrutinize the contribution of direct and indirect photodegradation processes in the elimination of micropollutants. The results show that photodegradation is most effective in the first 10 cm of the water column. A classification of micropollutants in 3 groups was developed to characterize their photodegradation. A significant increase of the half-life by direct photodegradation was observed in winter compared to summer due to a lower light intensity in winter. On the opposite, for direct + indirect photodegradation, no significant difference was observed between seasons. The decrease in light intensity in winter was compensated by higher nitrates concentration which promoted the formation of hydroxyl radicals and increased indirect photodegradation. The CW-photodegradation model successfully simulated the measured concentrations for direct and indirect photodegradation for 23 micropolluants. Nonetheless, it overestimated the indirect photodegradation with hydroxyl radicals when using default parameter values derived for surface waters. Hence, the consumption of hydroxyl radicals was increased by a factor of 20 for treated water. This model highlighted the predominance of direct photodegradation in the elimination of all micropollutants, except sotalol for the winter campaign.


Assuntos
Radical Hidroxila/química , Praguicidas/metabolismo , Fotólise/efeitos da radiação , Estações do Ano , Águas Residuárias/química , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Praguicidas/análise , Praguicidas/efeitos da radiação , Luz Solar , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/efeitos da radiação , Áreas Alagadas
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