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1.
Adv Exp Med Biol ; 1232: 375-381, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31893434

RESUMO

The value of optical redox imaging (ORI) of cells/tissues based on the intrinsic fluorescences of NADH (nicotinamide adenine dinucleotide) and oxidized flavoproteins (containing flavin adenine dinucleotide, i.e., FAD) has been demonstrated for potential biomedical applications including diagnosis, prognosis, and determining treatment response. However, the Chance redox scanner (a 3D cryogenic tissue imager) is limited by spatial resolution (~50 µm), and tissue ORI using fluorescence microscopy (single or multi-photon) is limited by the light penetration depth. Furthermore, viable or snap-frozen tissues are usually required. In this project, we aimed to study whether ORI may be achieved for unstained fixed tissue using a state-of-the-art modern Serial Two-Photon (STP) Tomography scanner that can rapidly acquire multi-plane images at micron resolution. Tissue specimens of mouse muscle, liver, and tumor xenografts were harvested and fixed in 4% paraformaldehyde (PFA) for 24 h. Tissue blocks were scanned by STP Tomography under room temperature to acquire the autofluorescence signals (NADH channel: excitation 750 nm, blue emission filter; FAD channel: excitation 860 nm, green emission filter). We observed remarkable signals with significant intra-tissue heterogeneity in images of NADH, FAD and redox ratio (FAD/(NADH+FAD)), which are worthy of further investigation for extracting biological information.


Assuntos
Tecnologia Biomédica , NAD , Imagem Óptica , Animais , Tecnologia Biomédica/instrumentação , Tecnologia Biomédica/métodos , Estudos de Viabilidade , Flavina-Adenina Dinucleotídeo , Xenoenxertos/diagnóstico por imagem , Camundongos , Oxirredução , Fótons
2.
Chemosphere ; 240: 124912, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574437

RESUMO

In this work, the combination of biological and electrochemical processes to mineralize oxyfluorfen has been studied. First, an acclimatized mixed-culture biological treatment was used to degrade the biodegradable fraction of the pesticide, reaching up to 90% removal. After that, the non-biodegraded fraction was oxidised by electrolysis using boron-doped diamond as the anode. The results showed that the electrochemical technique was able to completely mineralize the residual pollutants. The study of the influence of the supporting electrolyte on the electrochemical process showed that the trace mineral solution used in the biological treatment was enough to completely mineralize the oxyfluorfen, resulting in total organic carbon removal rates that were well-fitted by a first-order model with a kinetic constant of 0.91 h-1. However, the first-order degradation rate increased approximately 20% when Na2SO4 was added as supporting electrolyte, reaching a degradation rate of 1.16 h-1 with a power consumption that was approximately 70% lower.


Assuntos
Eletrólise/métodos , Éteres Difenil Halogenados/química , Éteres Difenil Halogenados/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo , Reatores Biológicos/microbiologia , Boro , Diamante , Eletrodos , Eletrólise/instrumentação , Cinética , Oxirredução , Praguicidas/química , Praguicidas/metabolismo , Sulfatos/química , Eliminação de Resíduos Líquidos/métodos
3.
Chemosphere ; 239: 124635, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514013

RESUMO

A comprehensive pilot study was carried out to experimentally assess the potential of newly developed treatment trains integrating two-stage AOPs and biofiltration to reach potable reuse water quality standards from municipal wastewater. The processes consisted of a two-stage AOPs with (carbon or limestone) biofiltration, the first AOP (O3/H2O2) serving as pre-treatment to biofiltration and the second AOP (UV254/H2O2) serving as post-biofiltration finishing step to ensure advanced disinfection. A comprehensive monitoring campaign was put in place resulting from the combination of targeted, non-targeted and suspect screening measurements. It was found that 13 organic micropollutants were detected from a list of 219 suspects although at ng/L level only. For the treatment conditions piloted in this study (O3 = 13 ±â€¯0.5 mg/L, H2O2 = 11 ±â€¯0.4 mg/L for the O3/H2O2 process, and UV = 410 ±â€¯63.5 mJ/cm2, H2O2 = 5 mg/l for the UV254/H2O2 process), it was possible to estimate the overall removal efficacy for each unit process, which was found to follow this order: RO (99%)  > BAC (87%) > O3-H2O2 (78%)  > BAL (67%)  > UV/H2O2 (43%)  > AOP contact chamber (19%)  > UF(0%), with the treatment train integrating two AOPs and granular biofiltration with activated carbon (O3/H2O2 + BAC + UV254/H2O2) showing superior performance with a 99% abatement in total micropollutants. No ecotoxicologically-positive response was generally observed for any of the effluent samples from the tested trains, even when pre-concentration factors up to 100-1000 times were employed to increase the sensitivity of the bioassay methods.


Assuntos
Água Potável/química , Filtração/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Carvão Vegetal/química , Desinfecção , Peróxido de Hidrogênio/química , Oxirredução , Ozônio/química , Projetos Piloto , Raios Ultravioleta
4.
Chemosphere ; 240: 124921, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726593

RESUMO

The interplay of phenolic molecules with 3d transition metals, such as Fe and Cu, and their oxide surfaces, provide important fingerprints for environmental burdens associated with thermal recycling of e-waste and subsequent generation of notorious dioxins compounds and phenoxy-type Environmental Persistent Free Radicals (EPFRs). DRIFTS and EPR measurements established a strong interaction of the phenol molecule with transition metal oxides via synthesis of phenolic- and catecholic-type EPFRs intermediates. In this contribution, we comparatively examined the dissociative adsorption of a phenol molecule, as the simplest model for phenolic-type compounds, on Cu and Fe surfaces and their partially oxidized configurations through accurate density functional theory (DFT) studies. The underlying aim is to elucidate the specific underpinning mechanism forming phenoxy- or phenolate-type EFPRs. Simulated results show that, the phenol molecule undergoes fission of its hydroxyl's O-H bond via accessible activation energies. These values are lower by 46.5-74.1% when compared with the analogous gas phase value. Physisorbed molecules of phenol incur very low binding energies in the range of -2.1 to -5.5 over clean Cu/Fe and their oxides surfaces. Molecular attributes based on charge transfer and geometrical features are in accord with the very weak interaction in physisorbed states. Thermo-kinetic parameters established over the temperature region of 300 and 1000 K, exhibit a lower activation energy for scission of phenolic's O-H bonds over the oxide surfaces in reference to their pure surfaces (24.7 and 43.0 kcal mol-1vs 38.4 and 47.0 kcal mol-1).


Assuntos
Radicais Livres/química , Fenol/química , Fenóis/química , Adsorção , Catecóis , Dioxinas , Radical Hidroxila , Oxirredução , Óxidos/química , Temperatura Ambiente , Elementos de Transição
5.
Chemosphere ; 238: 124579, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31434045

RESUMO

Nitroimidazoles are found in pharmaceuticals and personal care products (PPCPs) and, when discharged into the environment, have adverse effects on human health and survival. Advanced oxidation technologies (AOTs) based on persulfate (PS) can rapidly and efficiently degrade organic pollutants via strong oxidizing radicals under activation conditions. This study investigated the degradation of ronidazole (RNZ) by indirect electrolytic generation of PS and its activator, ferrous ion (Fe2+). An electrochemical system was developed, with a high concentration of PS generated at the anode while the activator Fe2+ was produced at the cathode. It showed that ammonium polyphosphate (APP) could effectively promote the electrolysis of PS. A high current efficiency (88%) at the anode could be obtained after 180 min at a high current density (300 mA cm-2). However, Fe2+ was inhibited at the cathode due to material control. The degradation of RNZ in the Fe2+/PS system generated from the electrochemical system was also explored. Increasing PS concentration and Fe2+/PS ratio were beneficial to the RNZ degradation. In homogeneous reactions, the degradation efficiency of RNZ could be improved by decreasing the Fe2+ addition rate through a peristaltic pump. Five intermediates were also detected and the degradation pathways were proposed. These findings provide a new method and mechanism for rapid and efficient degradation of RNZ.


Assuntos
Recuperação e Remediação Ambiental/métodos , Compostos Ferrosos/química , Ronidazole/metabolismo , Sulfatos/química , Poluentes Químicos da Água/análise , Técnicas Eletroquímicas , Eletrodos , Eletrólise , Ferro , Oxirredução
6.
Chemosphere ; 238: 124570, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31437629

RESUMO

Inhibition of anammox activities was tested with two ranges of chloramphenicol (CAP) concentration (5, 10, 20, 50, and 100 mg L-1) and (100, 500, and 1000 µg L-1). In a short-term study, strong inhibition of activity was dependent of CAP concentration in both attached-growth (SBR-A) and suspended-growth (SBR-S) systems. The activities of attached-growth cultures at all CAP concentrations were reversible after 1 day, while activities for suspended-growth cultures were only gradually reversible dependent on the CAP concentrations. In long-term studies with daily additions of 6 mg L-1 CAP, the anammox activity on day 41 in SBR-A had decreased to 18% baseline (SAA reduced from 0.528 to 0.096 mg N mg-1 VSS d-1). More rapid reduction of anammox activity was observed in SBR-S, down to 17% baseline after only 27 days (SAA decreased from 0.576 to 0.096 mg N mg-1 VSS d-1). Inhibition was irreversible in both SBR-S and SBR-A after the long-term study. With lower CAP additions (100-1000 µg L-1), the activities in both reactors were stable during daily CAP addition for two weeks. Attached-growth cultures tended to be more tolerant of CAP addition than suspended-growth cultures. Both un-competitive and non-competitive models could be used to compare anammox activities with the higher CAP concentrations. The SAAmax [fx] (the maximum specific anammox activity) and hKi (the inhibition constant) of SBR-A were 0.48 mg N mg-1 VSS d-1 and 98.3 mg L-1, respectively. The SAAmax[fx] and Ki of SBR-S were 1.25 mg N mg-1 VSS d-1and 71.1 mg L-1, respectively.


Assuntos
Compostos de Amônio/metabolismo , Antibacterianos/farmacologia , Bactérias Anaeróbias/crescimento & desenvolvimento , Bactérias Anaeróbias/metabolismo , Reatores Biológicos/microbiologia , Cloranfenicol/farmacologia , Anaerobiose , Nitrogênio , Oxirredução
7.
Chemosphere ; 238: 124575, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31446274

RESUMO

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


Assuntos
Técnicas Eletroquímicas/métodos , Glicina/análogos & derivados , Água Subterrânea/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Purificação da Água/métodos , Ácidos Carboxílicos/análise , Diamante/química , Eletrodos , Glicina/análise , Oxidantes/química , Oxirredução , Raios Ultravioleta
8.
Chemosphere ; 238: 124597, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31450106

RESUMO

In this study, we focused on the proportion of particular bacterial groups and changes in microbial community structure in relation to the anammox process parameters and the feeding medium strategy in the Sequencing Batch Reactor (SBR). In order to present an insight into the microbial dynamics while feeding medium shift from synthetic wastewater to landfill leachate, fluorescent in situ hybridization (FISH), Real Time PCR, PCR - DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis) and Reverse Transcription PCR-DGGE analysis were used. Feeding medium change has the strongest impact on relative abundance of denitrifiers and representatives of Planctomycetes. The relative abundancy of specific genes for all investigated nitrogen removal bacterial groups dropped after landfill leachate implementation. However, anammox consortium were able to adapt to the new reactor operating conditions and time for adaptation was estimated at the level of 90 days.


Assuntos
Compostos de Amônio/metabolismo , Reatores Biológicos/microbiologia , Planctomycetales/metabolismo , Águas Residuárias/química , Poluentes Químicos da Água/metabolismo , Eletroforese em Gel de Gradiente Desnaturante , Desnitrificação/fisiologia , Hibridização in Situ Fluorescente , Nitrogênio/metabolismo , Oxirredução , Planctomycetales/genética
9.
Chemosphere ; 238: 124625, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31466008

RESUMO

The cyanotoxin cylindrospermopsin was discovered during a drinking water-related outbreak of human poisoning in 1979. Knowledge about the degradation of cylindrospermopsin in waterbodies is limited. So far, only few cylindrospermopsin-removing bacteria have been described. Manganese-oxidizing bacteria remove a variety of organic compounds. However, this has not been assessed for cyanotoxins yet. We investigated cylindrospermopsin removal by manganese-oxidizing bacteria, isolated from natural and technical systems. Cylindrospermopsin removal was evaluated under different conditions. We analysed the correlation between the amount of oxidized manganese and the cylindrospermopsin removal, as well as the removal of cylindrospermopsin by sterile biogenic oxides. Removal rates in the range of 0.4-37.0 µg L-1 day-1 were observed. When MnCO3 was in the media Pseudomonas sp. OF001 removed ∼100% of cylindrospermopsin in 3 days, Comamonadaceae bacterium A210 removed ∼100% within 14 days, and Ideonella sp. A288 and A226 removed 65% and 80% within 28 days, respectively. In the absence of Mn2+, strain A288 did not remove cylindrospermopsin, while the other strains removed 5-16%. The amount of manganese oxidized by the strains during the experiment did not correlate with the amount of cylindrospermopsin removed. However, the mere oxidation of Mn2+ was indispensable for cylindrospermopsin removal. Cylindrospermopsin removal ranging from 0 to 24% by sterile biogenic oxides was observed. Considering the efficient removal of cylindrospermopsin by the tested strains, manganese-oxidizing bacteria might play an important role in cylindrospermopsin removal in the environment. Besides, manganese-oxidizing bacteria could be promising candidates for biotechnological applications for cylindrospermopsin removal in water treatment plants.


Assuntos
Toxinas Bacterianas/análise , Burkholderiales/metabolismo , Comamonadaceae/metabolismo , Manganês/metabolismo , Pseudomonas/metabolismo , Uracila/análogos & derivados , Purificação da Água/métodos , Água Potável/metabolismo , Compostos de Manganês/metabolismo , Oxirredução , Óxidos/metabolismo , Uracila/análise
10.
Chemosphere ; 238: 124632, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31472355

RESUMO

Fenton (Fe2+ + H2O2) reagents acting to remove organic pollutants possess dual functions, including the oxidation by hydroxyl radicals and the coagulation of Fe(III). Previous papers have extensively studied the oxidation reactions by hydroxyl radicals, however, the coagulation role of Fenton for benzoic acid (BA) removal is not clear. Comparing three coagulation systems, it was found that Fenton coagulation possesses a significant advantage for the removal of BA. Through Fenton conditional experiments, results showed that with the increase of H2O2 dosage, not only was the Fenton oxidation effect improved, but the Fenton coagulation effect was also significantly enhanced. Interestingly, the flocs produced by in situ Fenton possess a better coagulation effect than an aged Fenton system when processing BA. To further explain these results, Zeta potential, Transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray absorption fine structure (EXAFS) and Brunner-Emmet-Teller (BET) measurements were used for characterization, and we found that the flocs produced by Fenton possessed a smaller particle size, lower polymerization states and a larger specific surface area and pore volume, which exposed more active sites to create a better coagulation effect. Additionally, through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Gas chromatography-mass spectrometer (GC-MS), we found that in situ Fenton oxidation and coagulation have synergistic effects, and the carboxyl-containing intermediates produced by the Fenton oxidation of BA can be combined with hydroxyl active sites of the flocs produced by in situ Fenton, resulting in a better removal effect. Finally, Fenton oxidation increases oxygen/carbon (O/C) to promote Fenton coagulation, and in situ Fenton more fully utilizes the active sites on the flocs' surface.


Assuntos
Ácido Benzoico/análise , Peróxido de Hidrogênio/química , Ferro/química , Esgotos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Floculação , Radical Hidroxila/química , Oxirredução , Espectroscopia Fotoeletrônica , Difração de Raios X
11.
Chemosphere ; 238: 124628, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524606

RESUMO

This work investigated the improvement performances and mechanisms of waste activated sludge (WAS) dewaterability and the transformation behavior of heavy metals (HMs, including Cu, Zn, Pb, Cd and Cr) by jointly conditioning of Fe2+-activated peroxymonosulfate (PMS) oxidation and rice straw biochar (RS-BC). Experimental results showed that at original WAS pH of 6.5, the joint conditioning was the most effective when PMS dosage was 0.6 mmol·(g-volatile solids (VS))-1, Fe2+/PMS molar ratio was 0.6 and RS-BC dosage was 120 mg·(g-VS)-1. Under this condition, the lowest moisture content (MC) was 38.5% and the standardized-capillary suction time (SCST) was as high as 8.74. For the improvement mechanism, Fe2+-activated PMS oxidation can significantly disintegrate the extracellular polymeric substances (EPS) composing WAS to release EPS-bound water, and the RS-BC was helpful to form porous structures to improve WAS compressibility, facilitating the subsequent dewatering. In addition, Fe2+-activated PMS oxidation can obviously improve the solubilization and reduce the leaching toxicity of Cu, Zn, Pb, Cd and Cr, which was further enhanced by RS-BC. Therefore, the joint application of Fe2+-activated PMS oxidation and RS-BC can be a feasible way to improve WAS dewaterability and reduce HMs risk during WAS dewatering.


Assuntos
Carvão Vegetal/química , Metais Pesados/química , Oryza/química , Peróxidos/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Dessecação/métodos , Oxirredução
12.
Chemosphere ; 238: 124687, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524622

RESUMO

The development of highly efficient and green catalytic oxidation process based on peroxymonosulfate (PMS) activation has been identified to be a significant yet challenging objective in the environmental catalysis field. A simple, environmentally benign and highly effective catalytic oxidation system was innovatively constructed by coupling NaBO2 and PMS for the removal of Acid Red 1. The catalytic mechanism in the NaBO2/PMS system was elucidated by electron paramagnetic resonance (EPR) combined with several radical capture reagents (ascorbic acid, methanol, tert-butyl alcohol, ethanol and l-histidine). The experimental results indicated that singlet oxygen (1O2) severed as the predominant reactive oxygen species (ROS) rather than the HO or during the catalytic oxidation process, at variance with the reported radical pathway in the Co2+/PMS system. Inspiringly, p-benzoquinone (p-BQ) as a trapping agent in most advanced oxidation process could be turned into the positive one in the NaBO2/PMS system, achieving a nearly 3-times enhancement in terms of the rate constant for AR1 removal. More interestingly, sodium chloride (NaCl) presented the same enhancement effect as p-benzoquinone due to generation of hypochlorous acid (HOCl) and more 1O2, which was completely different from the reported. This study develops a highly efficient green oxidation process and opens up a new insight in the remediation of contaminated water.


Assuntos
Boratos/química , Oxirredução , Peróxidos/química , Rodaminas/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Catálise , Oxigênio Singlete/metabolismo
13.
Chemosphere ; 238: 124627, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31548173

RESUMO

Nitrogen contamination remains a severe environmental problem and a major threat to sustainable development worldwide. A systematic analysis of the literature indicates that the partial nitritation-anammox (PN/AMX) process is still actively studied as a viable option for energy-efficient and feasible technology for the sustainable treatment of N- rich wastewaters, since its initial discovery in 1990. Notably, the mainstream PN/AMX process application remains the most challenging bottleneck in AMX technology and fascinates the world's attention in AMX studies. This paper discusses the recent trends and developments of PN/AMX research and analyzes the results of recent years of research on the PN/AMX from lab-to full-scale applications. The findings would deeply improve our understanding of the major challenges under mainstream conditions and next-stage research on the PN/AMX process. A great deal of efforts has been made in the process engineering, PN/AMX bacteria populations, predictive modeling, and the full-scale implementations during the past 22 years. A series of new and excellent experimental findings at lab, pilot and full-scale levels including good nitrogen removal performance even under low temperature (15-10 °C) around the world were achieved. To date, pilot- and full-scale PN/AMX have been successfully used to treat different types of industrial sewage, including black wastewater, sludge digester liquids, landfill leachate, monosodium glutamate wastewater, etc. Supplementing the qualitative analysis, this review also provides a quantitative bibliometrics study and evaluates global perspectives on PN/AMX research published during the past 22 years. Finally, general trends in the development of PN/AMX research are summarized with the aim of conveying potential future trajectories. The current review offers a valuable orientation and global overview for scientists, engineers, readers and decision makers presently focusing on PN/AMX processes.


Assuntos
Compostos de Amônio/análise , Bactérias/metabolismo , Reatores Biológicos/microbiologia , Esgotos/química , Poluentes Químicos da Água/química , Bibliometria , Nitrogênio/análise , Oxirredução , Esgotos/microbiologia , Glutamato de Sódio/análise
14.
Chemosphere ; 238: 124854, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31549676

RESUMO

This work focusses on the production of hydrogen peroxide and in the removal of bromacil by the electro-Fenton process using two different electrochemical cells: mixed tank cell (MTC) and flow-through cell (FTC). Both cells use boron doped diamond (BDD) as anode and carbon felt as cathode to promote the formation of hydrogen peroxide. In the case of the MTC, two surface area ratios, Acathode/Aanode, have been used. Results show that the H2O2 produced by MTC and FTCPSC increases with the time until a stabilization state. For the FTCPSC, the average hydrogen peroxide concentration produced increases progressively with the current, while for MTC the maximum values are found in applying very low current densities. In addition, the FTCPSC provides higher concentrations of hydrogen peroxide for the same current density applied. Regarding the MTC, it can be stated that the higher the area of the cathode, the higher is the amount of H2O2 produced and the lower is the cell voltage (because of a more efficient current lines distribution). The initial oxidation of bromacil is very efficiently attained being rapidly depleted from wastewater. However, the higher production of hydrogen peroxide obtained by the FTCPSC cell does not reflect on a better performance of the electro-Fenton process. Thus, bromacil is better mineralized using the MTC cell with the lowest cathode area. This observation has been explained because larger concentrations of produced hydrogen peroxide seems to benefit the oxidation of intermediates and not the mineralization.


Assuntos
Bromouracila/análogos & derivados , Diamante/química , Peróxido de Hidrogênio/síntese química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Boro/química , Bromouracila/análise , Carbono/química , Condutividade Elétrica , Ferro/química , Oxirredução
15.
Chemosphere ; 239: 124686, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31494321

RESUMO

Oxidative degradation of aniline in aqueous solution was performed by the sono-activated peroxydisulfate coupled with PbO process, wherein a dramatic synergistic effect was found. Experiments were carried out in the batch-wise mode to investigate the influence of various operation parameters on the sonocatalytic behavior, such as ultrasonic power intensity, peroxydisulfate anion concentrations and PbO dosages. According to the scavenging effect of ethanol, methanol and tert-butyl alcohol, the principal oxidizing agents were presumed to be sulfate radicals descended from peroxydisulfate anions, activated via ultrasound or sonocatalysis of PbO. Based on the results attained from gas chromatograph-mass spectrometer, it was hypothesized that aniline was initially oxidized into iminobenzene radicals, followed with formation of nitrosobenzene, p-benzoquinonimine and nitrobenzene respectively. Condensation of nitrosobenzene with aniline generated azobenzene. Phenol was detected as one of degradation intermediates, which was sequentially converted into hydroquinone and p-benzoquinone.


Assuntos
Compostos de Anilina/química , Chumbo/química , Óxidos/química , Fenol/química , Sulfatos/química , Compostos Azo/síntese química , Benzoquinonas/síntese química , Etanol/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Hidroquinonas/síntese química , Metanol/metabolismo , Nitrobenzenos/síntese química , Compostos Nitrosos/síntese química , Oxidantes , Oxirredução , Semicondutores , Ondas Ultrassônicas , terc-Butil Álcool/metabolismo
16.
Chemosphere ; 239: 124670, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31505441

RESUMO

The objectives of this study were to determine the viability of removing Orange II (OII) dye by simulated solar photoelectro-Fenton (SSPEF) and to evaluate the stability of a WO2.72/Vulcan XC72 gas diffusion electrode (GDE) and thus determine its best operating parameters. The GDE cathode was combined with a BDD anode for decolorization and mineralization of 350 mL of 0.26 mM OII by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) at 100, 150 and 200 mA cm-2 and SSPEF at 150 mA cm-2. The GDE showed successful operation for electrogeneration, good reproducibility and low leaching of W. Decolorization and OII decay were directly proportional to the current density (j). AO-H2O2 had a reduced performance that was only half of the SSPEF, PEF and EF treatments. The mineralization efficiency was in the following order: AO-H2O2 < EF < PEF ≈ SSPEF. This showed that the GDE, BDD anode and light radiation combination was advantageous and indicated that the SSPEF process is promising with both a lower cost than using UV lamps and simulating solar photoelectro-Fenton process. The PEF process with the lowest j (100 mA cm-2) showed the best performance-mineralization current efficiency.


Assuntos
Compostos Azo/análise , Benzenossulfonatos/análise , Técnicas Eletroquímicas , Peróxido de Hidrogênio/química , Ferro/química , Poluentes Químicos da Água/análise , Eletrodos , Oxirredução , Reprodutibilidade dos Testes , Luz Solar
17.
Int J Food Microbiol ; 312: 108387, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31669763

RESUMO

Fresh produce-associated outbreaks of foodborne illnesses continue to occur every year in the U.S., suggesting limitations of current practices and the need for effective intervention technologies. Advanced oxidation process involves production of hydrogen radicals, which are the strongest oxidant. The objective of the present study was to evaluate the effectiveness of advanced oxidation process by combining gaseous ozone and aerosolized hydrogen peroxide. Grape tomatoes were inoculated with a 2-strain cocktail of Salmonella typhimurium on both stem scar and smooth surface. Gaseous ozone (800 and 1600 ppm) and aerosolized hydrogen peroxide (2.5, 5 and 10%) were separately or simultaneously introduced into a treatment chamber where the inoculated tomatoes were placed. During the 30 min treatments, hydrogen peroxide was aerosolized using an atomizer operated in two modes: continuously or 15 s on/50 s off. After the treatments, surviving Salmonella on the smooth surface and stem scar were enumerated. Results showed that ozone alone reduced Salmonella populations by <0.6 log CFU/fruit on both the smooth surface and the stem scar area, and aerosolized hydrogen peroxide alone reduced the populations by up to 2.1 log CFU/fruit on the smooth surface and 0.8 log CFU/fruit on stem scar area. However, the combination treatments reduced the populations by up to 5.2 log CFU/fruit on smooth surface and 4.2 log CFU/fruit on the stem scar. Overall, our results demonstrate that gaseous ozone and aerosolized hydrogen peroxide have synergistic effects on the reduction of Salmonella populations on tomatoes.


Assuntos
Doenças Transmitidas por Alimentos/prevenção & controle , Peróxido de Hidrogênio/farmacologia , Lycopersicon esculentum/microbiologia , Ozônio/farmacologia , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Microbiologia de Alimentos/métodos , Frutas/microbiologia , Oxirredução
18.
Chemosphere ; 239: 124743, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514007

RESUMO

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO2 and ZIF-67 were used as precursors to prepare MoO2@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C-N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (-0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H2O2 concentrations (62.5 mg L-1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)-OH could get the electron directly from the cathode, which would greatly reduce the consumption of H2O2, high utilization efficiency of H2O2 (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.


Assuntos
Cobalto/química , Ácido Edético/química , Técnicas Eletroquímicas/métodos , Nanopartículas Metálicas/química , Níquel/química , Catálise , Descontaminação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Grafite/química , Peróxido de Hidrogênio/química , Ferro/química , Nitrogênio/química , Oxirredução , Piridinas/química , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos
19.
Chemosphere ; 238: 124611, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524605

RESUMO

An eco-friendly material, activated carbon cloth (ACC) was used as the heterogeneous catalyst in activation of peroxydisulfate (PDS) for the efficient degradation of organic pollutant in water. Besides, the effects of several parameters in the ACC/PDS process including initial pH, PDS concentration, reaction temperature, stirring speed and co-existing anions were investigated. Under optimum conditions, almost complete removal (98.6%) of AO7 in 60 min and 67.4% of total organic carbon (TOC) removal within 180 min were obtained, accompanied by the remarkable destruction of azo band and naphthalene ring on AO7. The electron paramagnetic resonance and radical quenching experiments were carried out to identify the reactive radicals in the ACC/PDS process. Surface characteristic techniques such as XRD, BET, SEM, FTIR, XPS were applied to analysis the change of crystal structure, surface area, surface morphology, functional groups on the surface of fresh and spent ACC samples. Hydroxyl groups (C‒OH) and π-π transitions significantly affected the catalytic activity of ACC. The intermediate products of AO7 oxidation were identified by LC-MS and the corresponding degradation pathway was proposed.


Assuntos
Compostos Azo/química , Carvão Vegetal/química , Sulfatos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Catálise , Recuperação e Remediação Ambiental , Oxirredução
20.
Chemosphere ; 240: 124929, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31561158

RESUMO

An UV enhanced electro-Fenton (EF) process was conducted in a flow-through system to remove rhodamine B (RhB) in the presence of ethylenediamine tetraacetate (EDTA). The process was denoted as UV/EDTA/EF where EDTA formed complexes with iron ions, thus keeping them soluble at high pH values. The process was very efficient as it could initiate the fast reduction of FeIII to FeII and thus the decomposition of H2O2. The influence of Fe dose, the ratio of EDTA:Fe, aeration rate, flow rate, current, initial RhB concentration and pH on the RhB removal in the UV/EDTA/EF process was investigated. The best RhB removal was obtained as 89.9% at [Fe]0 = [EDTA]0 = 0.2 mM, current = 50 mA, aeration rate = 20 mL min-1, flow rate = 7 mL min-1, pH = 7 and [Na2SO4]0 = 0.05 M. The degradation of EDTA during the process was also studied. Radical scavenging experiments indicated that OH was the dominant radical for RhB removal. While, the photolysis of FeIIIEDTA was mainly responsible for EDTA degradation. RhB and EDTA removal in different systems was compared. The stability test proved that in the presence of EDTA, the UV/EF process could remove RhB with high efficiency in the first two runs. While, the efficiency dropped remarkably after EDTA's complete depletion. The mechanisms of the UV/EDTA/EF process were proposed. UV/EDTA/EF conducted in the flow-through system was able to efficiently remove RhB as well as EDTA in a wide pH range and proposed as a promising approach for wastewater treatment.


Assuntos
Ácido Edético/análise , Peróxido de Hidrogênio/química , Ferro/química , Fotólise , Rodaminas/análise , Poluentes Químicos da Água/análise , Compostos Férricos/química , Cinética , Oxirredução , Águas Residuárias/química
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