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1.
Chemosphere ; 239: 124612, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31499301

RESUMO

The degradation of carboxylic acid has been identified as one of the rate-determining steps in the mineralization of organic pollutants by ozonation. In this study, Ce(III)-doped graphitic carbon nitride (Ce-CN) composites with different Ce(III) contents were synthesized and used as catalysts for the ozonation of oxalate. The morphology and structure of the Ce-CN were comprehensively characterized using various techniques such as SEM, XRD, FTIR, and XPS. The results show that the structure of g-C3N4 provided an ideal site for the accommodation of Ce(III) and thus facilitated the formation of surface hydroxyl groups. With 2.5%Ce-CN as a catalyst, the degradation efficiency of oxalate was increased by 47.1% after reaction for 30 min. The decomposition of ozone was accelerated in the presence of Ce-CN. Hydroxyl radicals were recorded by electron spin resonance and identified as the major actives species. Under the catalysis of 2.5%Ce-CN, the production of hydroxyl radicals was increased by 40%. The Ce(III) and surface hydroxyl groups that distributed uniformly on the surface of Ce-CN were speculated as the dual catalytic sites for the complexation of oxalate and activation of ozone, respectively. Ce-CN had a high stability and reutilization capability. It is proposed that a complex was formed between surface Ce(III) and oxalate, and this complex could be more easily attacked by the surrounding ozone and hydroxyl radicals than free oxalate. As oxalate is a typical recalcitrant carboxylic acid, the findings from this study are expected to promote the application of ozonation in the removal of organic pollutants.


Assuntos
Cério/química , Grafite/química , Compostos de Nitrogênio/química , Oxalatos/química , Ozônio/química , Poluentes Químicos da Água/química , Catálise , Radical Hidroxila/química , Compostos Orgânicos
2.
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
3.
Chemosphere ; 240: 124744, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31557643

RESUMO

The heterogeneous reactions of α-Al2O3 particles with a mixture of ozone (∼50 ppm) and isoprene (∼50 ppm) were studied as a function of relative humidities (RHs). The reactions were monitored in real time through the microscopic Fourier transform infrared (micro-FTIR) spectrometer. The results show that the presence of ozone leads to the rapid conversion of isoprene to carboxylate (COO-) ions on the surfaces of α-Al2O3 particles in the initial stage. The water significantly suppresses the formation of the carboxylate ions. For the isoprene ozonolysis reaction on the α-Al2O3 particles, the reactive uptake coefficient is strongly suppressed by over a factor of 8 when the RH increases from 8% to 89%. The negative correlation between RH with the secondary organic aerosol (SOA) produced by isoprene ozonolysis plays a key role in the actual atmospheric environment under high humidity. Our results may provide insight into the ozonolysis process of biogenic alkenes over mineral aerosol surfaces with the influence of RHs.


Assuntos
Butadienos/química , Hemiterpenos/química , Modelos Químicos , Ozônio/química , Aerossóis , Umidade , Água
4.
Chemosphere ; 238: 124694, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524628

RESUMO

Techniques for reutilization of the discarded bischofite are limited while efficient recovery of the Mg(OH)2 nanoparticles from water during the synthesis and reuse processes is a challenge. In this study, the Fe3O4@Mg(OH)2 core-shell magnetic nanoparticles were firstly prepared from discarded bischofite and used as catalyst for improving the ozonation of metronidazole (MNZ). The removal rate constant of MNZ increased by 694.7% using Fe3O4@Mg(OH)2. Compared with the Mg(OH)2 control, the MNZ removal rate constant of Fe3O4@Mg(OH)2 treatment was almost tripled. The persistent high catalytic activity of the Fe3O4@Mg(OH)2 catalyst was observed since the MNZ removal rate constant decreased by just 13.2% in the third reuse run. The Fe3O4@Mg(OH)2 primarily enhanced ozone decomposition through producing hydroxyl radicals. The MNZ removal rate constant increased from 0.075 min-1 to 0.643 min-1 as catalyst dose increased from 0 to 0.6 g L-1 while it decreased by 96.0% when its initial concentration increased from 10 to 200 mg L-1. The maximum removal rate constant was observed at 25 °C when temperature increased from 15 °C to 35 °C. The Cl-, HCO3-, SO42-, Ca2+, Mg2+ ions could jeopardize MNZ degradation. The antibacterial activity of MNZ was eliminated after catalytic ozonation while the mineralization efficiency was almost doubled. The nitro group reduction and the cleavage of hydroxyethyl bond were two main transformation pathways of MNZ. These findings suggest that Fe3O4@Mg(OH)2 nanoparticle made from discarded bischofite is the promising catalyst for the ozonation of antibiotics in the terms of water purification practice and reutilization of the bischofite.


Assuntos
Antibacterianos/análise , Hidróxido de Magnésio/química , Ozônio/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Antibacterianos/metabolismo , Catálise , Fenômenos Magnéticos , Nanopartículas de Magnetita/química , Poluentes Químicos da Água/metabolismo
5.
Chemosphere ; 238: 124618, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31470309

RESUMO

In this work, we employed surface-enhanced Raman spectroscopy (SERS) combined with density functional theory (DFT) calculation to investigate the pathways/mechanisms of the norfloxacin degradation by oxygen plasma produced ozone. The main degradation products were analyzed by the spectroscopic method, which revealed the breakage of the C-F bond and fracture of piperazinyl and quinolone moieties. In particular, we showed that the main degradation pathway was defluorination of norfloxacin, and this process could be quantitatively assessed by our proposed SERS approach.


Assuntos
Norfloxacino/análise , Norfloxacino/química , Ozônio/química , Gases em Plasma/química , Análise Espectral Raman/métodos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
6.
Chemosphere ; 240: 124928, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563101

RESUMO

Oxidation is an attractive treatment method to effectively remove organic contaminants in water. In this study, degradation of 30 organic compounds in different oxidation systems was evaluated, including oxygen (O2), hydrogen peroxide (H2O2), ozone (O3) and hydroxyl radical (HO). First, a quantitative structure-activity relationship (QSAR) model for oxidation-reduction potentials (ORPs) of organics was developed and exhibited a good performance to predict ORP values of organics with evaluation indices of squared correlation coefficient (R2) = 0.866, internal validation (q2) = 0.811 and external validation (Qext2) = 0.669. Four quantum parameters, including f(+)n, f(-)n, EHOMO and EB3LYP dominate the ORP values. Subsequently, a relationship between reaction rates (k) and the difference of ORP for oxidants and organics (ΔEoxi-org) was established, however, which was limited (R2= 0.697). Therefore, two new predictors (slopes and intercepts) are proposed based on the linear relationships between k values and ORPs of oxidants. These new predictors can be applied to estimate the reaction rates and minimum oxidation potential for organic compounds. Afterwards, to express the two predictors, QSAR models were established. The two optimal QSAR models fitted very well with experimental values and were demonstrated to be stable and accurate based on R2 (0.982 and 0.965), q2 (0.950 and 0.950) and Qext2 (0.985 and 0.989). BOx, q(H)+ and q(C)x were main factors influencing the slopes and intercepts. This study developed methods to predict ORPs of organics and established two new predictors to estimate the reaction rates undergoing different oxidation processes, offering new insights into the oxidant selection.


Assuntos
Modelos Teóricos , Compostos Orgânicos/análise , Relação Quantitativa Estrutura-Atividade , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Oxidantes/química , Oxirredução , Oxigênio/química , Ozônio/química , Águas Residuárias/química , Água
7.
Chemosphere ; 238: 124639, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31470311

RESUMO

This work investigated the feasibility of a hybrid process consisting of catalytic ozonation and biodegradation (i.e., sequencing batch reactor, SBR) for the treatment of the industrial-based reverse osmosis concentrate (ROC) with specific characteristics of high levels of total dissolved solids (TDS) and refractory pollutants. The Fe-based homogeneous and heterogeneous catalytic ozonation was in parallel investigated and compared in terms of contaminant removal efficiency and biodegradability variation. The Fe-based heterogeneous catalyst carried the higher potential to improve the biodegradability of ROC (i.e., 0.32 v. s. 0.27 for B/C, the ratio between BOD5 and COD) although its direct COD removal efficiency was inferior to the homogeneous one (i.e., 49% v. s. 59% after 25 min' reaction). The ROC pretreated by the Fe-based heterogeneous catalytic ozonation for 5 min was further treated by biodegradation. After the hybrid treatment, the COD concentration reached ∼40 mg/L meeting with the discharge standard (GB, 18918-2002), under the optimal reaction conditions of 2.0 L/min ozone flow rate for catalytic ozonation and 120 min' aeration for biodegradation. The solution pH should not be adjusted by taking both the treatment efficiency and operating cost into consideration. The treatment cost of the hybrid process was estimated to be 0.15 USD/m3. This work could provide a feasible and economic option for the proper management of the industrial-based ROC and should be of interest to the application fields.


Assuntos
Biodegradação Ambiental , Ozônio/química , Águas Residuárias/química , Purificação da Água/métodos , Catálise , Osmose , Eliminação de Resíduos Líquidos/economia , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Purificação da Água/economia
8.
Food Chem ; 309: 125761, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31757490

RESUMO

Innovative chemometric approaches by NMR and LC-MS data fusion (multiblock analysis) and decomposition of the GC-MS raw data by PARADISe were applied to evaluate the influence of thermal and non-thermal processing on the composition of cashew apple juices. Comparative investigations by Principal Component Analysis (PCA) highlighted pronounced effect of thermal processing on juice compared to non-thermal processing, as decreases of anacardic acids, sucrose, malic acid, tyrosine, phenylalanine, and important flavor compounds (esters, aldehydes, and ketones). Ultrasound presented relevant influence on increase of anacardic acids concentration. Non-thermal processing carried out at more intense conditions (10 min of ultrasound, 5 min of ozone, and pulsed light at 10 V) showed pronounced effect compared to other non-thermal processing. Although individual PCA enables to detect the influence of different processing technologies, data fusion and PARADISe presented advantages, since a more comprehensive understanding of the relationship among chemical changes from different analytical techniques were established.


Assuntos
Anacardium/química , Sucos de Frutas e Vegetais/análise , Ácidos Anacárdicos/análise , Anacardium/metabolismo , Cromatografia Líquida de Alta Pressão , Cromatografia Gasosa-Espectrometria de Massas , Temperatura Alta , Espectroscopia de Ressonância Magnética , Malatos/análise , Ozônio/química , Análise de Componente Principal , Sonicação , Espectrometria de Massas em Tandem , Raios Ultravioleta
9.
J Environ Sci (China) ; 87: 60-70, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31791518

RESUMO

The performance of Ce-OMS-2 catalysts was improved by tuning the fill percentage in the hydrothermal synthesis process to increase the oxygen vacancy density. The Ce-OMS-2 samples were prepared with different fill percentages by means of a hydrothermal approach (i.e. 80%, 70%, 50% and 30%). Ce-OMS-2 with 80% fill percentage (Ce-OMS-2-80%) showed ozone conversion of 97%, and a lifetime experiment carried out for more than 20 days showed that the activity of the catalyst still remained satisfactorily high (91%). For Ce-OMS-2-80%, Mn ions in the framework as well as K ions in the tunnel sites were replaced by Ce4+, while for the others only Mn ions were replaced. O2-TPD and H2-TPR measurements proved that the Ce-OMS-2-80% catalyst possessed the greatest number of mobile surface oxygen species. XPS and XAFS showed that increasing the fill percentage can reduce the AOS of Mn and augment the amount of oxygen vacancies. The active sites, which accelerate the elimination of O3, can be enriched by increasing the oxygen vacancies. These findings indicate that increasing ozone removal can be achieved by tuning the fill percentage in the hydrothermal synthesis process.


Assuntos
Modelos Químicos , Ozônio/química , Catálise , Manganês/química , Óxidos/química , Oxigênio
10.
Photochem Photobiol Sci ; 18(12): 2931-2941, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31696195

RESUMO

Recent studies show that the ozone layer will recover by the middle part of this century. This is a significant result arising from the Montreal Protocol, and highlights the success of this environmental protection agreement. Climate change projections show that Total Ozone Content (TOC) levels will increase significantly by the end of this century, mainly at higher latitudes. This increase may result in a reduction of the adverse effects of UV radiation overexposure. By contrast, reduced UV radiation levels at the surface of the Earth can result in reduced levels of vitamin D synthesis among the inhabitants of these regions. In this study we provide estimates for the UVI, erythemal, and vitamin-D weighted daily doses for ten different locations in South America and Antarctica. Our calculations were based on ozone projections provided by climate models set forth in the last IPCC report. Results show that the increase of TOC levels in middle and high latitude regions may result in decreased UVI and UV doses throughout the century. In high latitudes, erythemal doses and vitamin D synthesis doses may be reduced by up to 22 and 39%, respectively, if anthropogenic emissions continue to rise throughout the century. Furthermore, there may be reductions of up to 9 and 12%, respectively, in mid-latitudes (20°S to 35°S). Significant variations at Equatorial sites were not observed. In most of South America, the attenuation in UVR caused by increases in TOC during the 21st century is neither enough to promote protective effects from this radiation, nor for the lack of UVR for vitamin D synthesis. The incidence of UVR in tropical and sub-tropical areas of the continent will continue to be a public health risk for the entire 21st century during all seasons, regardless of the climatic scenarios. Our results can be used as an important tool for health studies focusing on the excess and/or lack of sun exposure.


Assuntos
Eritema/etiologia , Ozônio/química , Raios Ultravioleta , Vitamina D/biossíntese , Regiões Antárticas , Humanos , Estações do Ano , América do Sul , Raios Ultravioleta/efeitos adversos
11.
Ecotoxicol Environ Saf ; 186: 109768, 2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31606645

RESUMO

The studies on occurrence of contaminants of emerging concern in drinking water treatment plants or even wastewater treatment plants in developing country like India, are very limited. Trihalomethanes (THMs) is one such contaminant of concern in drinking water treatment sector. THMs are the major disinfection byproducts (DBPs) formed during the widely used chlorination process. Their identification and removal is of utmost importance in developed as well as developing nations. This study is first of its kind to assess the removal of mixture of urban run-off driven organic matter, agricultural run-off driven organic matter, untreated sewage effluent driven organic matter and little natural organic matter (NOM) (altogether NefOM) (major DBP precursors) using advanced oxidation processes (AOPs) in the Indian region. Since, NOM vary geographically, this study will add up to applicability of generally utilized AOPs for removal of site explicit (Indian) NefOM. Trihalomethanes at a conventional water treatment plant at Mathura and a moving bed biofilm based non-conventional water treatment plant at Agra were monitored over a year, demonstrating the inability of the water treatment plants to limit formation of DBPs from Yamuna inlet water at any time of the year. Various AOPs (UV-H2O2, O3-H2O2, O3) and UV (ultraviolet) photolysis were assessed for their ability to decrease the trihalomethane forming potential (THMFP) by degrading the contaminants in the waters of Yamuna. Kinetic studies were conducted to evaluate the selected AOPs based on their ability to mineralize dissolved organic carbon (DOC), and decrease UV254 at various pH, UV intensities, and ozone and hydrogen peroxide concentrations. UV-L/H2O2 at an intensity of 47 mJ/cm2/min, pH = 7, and at hydrogen peroxide concentration of 0.5 mM provided an optimum reduction of DOC (64%) and UV254 (87%). Fractionation studies indicated that treatment by UV-L/H2O2 leads to the most significant decrease in the hydrophobic fraction of the water, while further study indicated that UV-L/H2O2 also showed maximum attenuation of THMFP.


Assuntos
Cloro/química , Desinfecção/métodos , Trialometanos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Países em Desenvolvimento , Substâncias Húmicas/análise , Peróxido de Hidrogênio/química , Índia , Cinética , Oxirredução , Ozônio/química , Fotólise , Esgotos/química , Trialometanos/efeitos da radiação , Raios Ultravioleta , Águas Residuárias/química , Poluentes Químicos da Água/efeitos da radiação
12.
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
13.
Chemosphere ; 235: 1107-1115, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561301

RESUMO

Two analytical techniques - online Gas Chromatography coupled with Flame Ionization Detector (often used method for VOCs monitoring) versus Selected Ion Flow Tube coupled with Mass Spectrometry (a more recent technique based on direct mass spectrometry) - were compared in association to an ozone-based gas treatment. Selecting aldehydes as the representative VOCs, their concentrations were monitored during ozonation experiments by both techniques in parallel. Contradictory results were obtained in the presence of ozone. Aldehydes were up to 90% removed due to a reaction with ozone according to GC/FID analysis, whereas with SIFT/MS, aldehydes concentration remained at the same level during the experiments regardless of the ozone presence. In addition, it was demonstrated that the apparent aldehydes removal was affected by GC injector temperature, varying from 90% (when it was at 250 °C) to 60% (at 100 °C). Meanwhile, even when the ozonation reactor was heated to 100 °C, no aldehydes conversion was evidenced by SIFT/MS, suggesting that the GC injector temperature was not the only interference-causing parameter. The ozone-aldehyde reaction is probably catalyzed by some material of GC injector and/or column. An ozone-GC interference was therefore confirmed, making unsuitable the use of GC/FID with silicone stationary phase to monitor aldehydes in presence of high concentrations of ozone (at least 50 ppmv). On the other hand, SIFT/MS was validated as a reliable technique, which can be employed in order to measure VOCs concentrations in ozonation processes.


Assuntos
Aldeídos/análise , Ionização de Chama/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Ozônio/química , Aldeídos/química , Espectrometria de Massas/métodos , Reprodutibilidade dos Testes , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/química
14.
Int J Mol Sci ; 20(18)2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-31514377

RESUMO

The lignin pyrolysis products generated by biomass combustion make an essential contribution to the formation of secondary organic aerosols (SOAs). The ozone-initiated oxidation of guaiacol, syringol and creosol, major constituents of biomass burning, were investigated theoretically by using the density functional theory (DFT) method at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level. Six primary addition reaction pathways and further decomposition routes with corresponding thermodynamic values were proposed. The Criegee intermediates can be excited by small molecules, such as NOx, H2O in the atmosphere, and would further proceed via self-decomposition or isomerization. The most predominant product for ozonation of guaiacol is the monomethyl muconate (P1). At 295 K and atmospheric pressure, the rate constant is 1.10 × 10-19 cm3 molecule-1 s-1, which is lies a factor of 4 smaller than the previous experimental study. The branching ratios of the six channels are calculated based on corresponding rate coefficient. The present work mainly provides a more comprehensive and detailed theoretical research on the ozonation of methoxyphenol, which aspires to offer novel insights and reference for future experimental and theoretical work and control techniques of SOAs caused by lignin pyrolysis products.


Assuntos
Biomassa , Cresóis/química , Guaiacol/química , Ozônio/química , Pirogalol/análogos & derivados , Atmosfera/química , Cinética , Conformação Molecular , Pirogalol/química
15.
Molecules ; 24(16)2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31398794

RESUMO

Artificial sweeteners (ASWs), a class of emerging contaminants with good water solubility, have attracted much attention recently because of their wide use and negative impact on the aquatic environment and drinking water. Efficient technologies for removing ASWs are in urgent need. This study investigated degradation of typical ASW acesulfame by ozone-activated peroxymonosulfate process (O3/PMS) in prepared and real waters. O3/PMS can degrade >90% acesulfame in prepared water within 15 min at a low dosage of O3 (60 ± 5 µg∙min-1) and PMS (0.4 mM). Ozone, hydroxyl radical (HO•), and sulfate radical (SO4•-) were identified as contributors for ACE degradation and their contribution proportion was 27.1%, 25.4%, and 47.5% respectively. O3/PMS showed the best degradation performance at neutral pH and were sensitive to constituents such as chloride and natural organic matters. The qualitative analysis of degradation products confirmed the involvement of hydroxyl radical and sulfate radical and figured out that the active sites of ACE were the C=C bond, ether bond, and C-N bond. The electrical energy per order ACE degradation were calculated to be 4.6 kWh/m3. Our findings indicate that O3 is an efficient PMS activator and O3/PMS is promising due to its characteristic of tunable O3-HO• SO4•- ternary oxidant involving.


Assuntos
Oxirredução , Ozônio/química , Peróxidos/química , Tiazinas/química , Estrutura Molecular , Análise Espectral , Sulfatos/química , Poluentes Químicos da Água/química , Purificação da Água
16.
Int J Mol Sci ; 20(17)2019 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-31454911

RESUMO

The main aim of this work is to substantiate the mechanism of 1-propanol oxidation by ozone in aqueous solution when the substrate is present in large excess. Further goals are assessment of the products, their formation yields as well as the kinetic parameters of the considered reaction. The reaction of ozone with 1-propanol in aqueous solution occurs via hydride transfer, H-abstraction and insertion. Of these three mechanisms, the largest share is for hydride transfer. This implies the extraction of an hydride ion from the activated C-H group by O3 according to reaction: (C2H5)(H)(HO)C-H + O3 → [(C2H5)(H)(HO)C+ + HO3-]cage → (C2H5)(H)(HO)C+ + HO3-. The experimentally determined products and their overall formation yields with respect to ozone are: propionaldehyde-(60 ± 3)%, propionic acid-(27.4 ± 1.0)%, acetaldehyde-(4.9 ± 0.3)%, acetic acid-(0.3 ± 0.1)%, formaldehyde-(1.0 ± 0.1)%, formic acid-(4.6 ± 0.3)%, hydrogen peroxide-(11.1 ± 0.3)% and hydroxyl radical-(9.8 ± 0.3)%. The reaction of ozone with 1-propanol in aqueous media follows a second order kinetics with a reaction rate constant of (0.64 ± 0.02) M-1·s-1 at pH = 7 and 23 °C. The dependence of the second order rate constant on temperature is described by the equation: l n   k I I = ( 27.17 ± 0.38 ) - ( 8180 ± 120 ) × T - 1 , which gives the activation energy, Ea = (68 ± 1) kJ mol-1 and pre-exponential factor, A = (6.3 ± 2.4) × 1011 M-1 s-1. The nature of products, their yields and the kinetic data can be used in water treatment. The fact that the hydride transfer is the main pathway in the 1-propanol/ozone system can probably be transferred on other systems in which the substrate is characterized by C-H active sites only.


Assuntos
1-Propanol/química , Ozônio/química , Ácidos/química , Aldeídos/metabolismo , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Modelos Químicos , Água/química
17.
Chemistry ; 25(62): 14101-14107, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31429133

RESUMO

A de novo solid-phase synthesis of the cyclic lipodepsipeptide daptomycin via Boc chemistry was achieved. The challenging ester bond formation between the nonproteinogenic amino acid kynurenine was achieved by esterification of a threonine residue with a protected tryptophan. Subsequent late-stage on-resin ozonolysis, inspired by the biomimetic pathway, afforded the kynurenine residue directly. Synthetic daptomycin possessed potent antimicrobial activity (MIC100 =1.0 µg mL-1 ) against S. aureus, while five other daptomycin analogues containing (2R,3R)-3-methylglutamic acid, (2S,4S)-4-methylglutamic acid or canonical glutamic acid at position twelve prepared using this new methodology were all inactive, clearly establishing that the (2S,3R)-3-methylglutamic acid plays a key role in the antimicrobial activity of daptomycin.


Assuntos
Anti-Infecciosos/síntese química , Daptomicina/síntese química , Cinurenina/química , Ozônio/química , Anti-Infecciosos/química , Daptomicina/análogos & derivados , Avaliação Pré-Clínica de Medicamentos , Glutamatos/química , Ácido Glutâmico/análogos & derivados , Ácido Glutâmico/química , Técnicas de Síntese em Fase Sólida , Staphylococcus aureus/efeitos dos fármacos , Treonina/química
18.
Mar Pollut Bull ; 146: 696-702, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426211

RESUMO

This study investigated the removal of microplastics from different treatment stages in three WWTPs and examined the performance of tertiary treatment that was done by coagulation and different technologies such as ozone (WWTP-A), membrane disc-filter (WWTP-B), and rapid sand filtration (WWTP-C). The results showed that the primary and secondary treatment processes effectively remove microplastics from wastewater with efficiencies ranging between 75% and 91.9%. The removal efficiency increased further to >98% after tertiary treatment. Microbeads and fragments were the major types of microplastics found in all wastewater sampling points. Microbeads found in the wastewater samples were classified as primary microplastics, that mainly came from personal care products, whereas secondary microplastics consisted of fragments, fibers, and sheets that were generated mainly due to fragmentation of larger plastics. Microplastics were still found in a high concentration in the final effluent, especially from WWTP-B, which is discharged into the Geumho river.


Assuntos
Plásticos/análise , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/análise , Poluentes Químicos da Água/análise , Filtração/métodos , Ozônio/química , Plásticos/química , Plásticos/isolamento & purificação , República da Coreia , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação
19.
J Sci Food Agric ; 99(15): 6814-6821, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31368532

RESUMO

BACKGROUND: Maize is one of the most important cereals. It is used for different purposes and in different industries worldwide. This cereal is prone to contamination with mycotoxins, such as zearalenone (ZEN), which is produced mainly by Fusarium graminearum, F. culmorum and F. equiseti. Toxin production under highly moist conditions (aw > 0.95) is exacerbated if there are alternations between low temperatures (12-14 °C) and high temperatures (25-28 °C). Even if good production practices are adopted, mycotoxins can be found in several stages of the production chain. For this reason, an alternative to reducing this contamination is ozonation. This study evaluated the reduction of ZEN in naturally contaminated whole maize flour (WMF) treated with 51.5 mg L-1 of ozone for up to 60 min. Pasting properties, peroxide value, and fatty acid composition were also evaluated. RESULTS: Zearalenone degradation in ozonated WMF was described by a fractional first-order kinetic, with a maximum reduction of 62.3% and kinetic parameter of 0.201 min-1 in the conditions that were evaluated. The ozonation process in WMF showed a decrease in the apparent viscosity, a decrease in the proportion of linoleic, oleic, and α-linolenic fatty acids, an increase in the proportion of palmitic acid, and an increase in the peroxide value. CONCLUSION: Ozonation was effective in reducing ZEN contamination in WMF. However, it also modified the pasting properties, fatty acid profile, and peroxide value, affecting functional and technological aspects of WMF. © 2019 Society of Chemical Industry.


Assuntos
Descontaminação/métodos , Ozônio/farmacologia , Zea mays/química , Zearalenona/química , Descontaminação/instrumentação , Contaminação de Alimentos/análise , Fusarium/metabolismo , Cinética , Ozônio/química , Controle de Qualidade , Zea mays/efeitos dos fármacos , Zea mays/microbiologia , Zearalenona/metabolismo
20.
Molecules ; 24(15)2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31362453

RESUMO

The textile wash-off process consumes substantial amounts of water, which generates large volumes of wastewater that pose potential pollution issues for the environment. In the present study, catalytic ozonation was applied to degrade residual dyes present in rinsing effluents from wash-off processes towards the aim of recycling the waste effluents. A magnetic catalyst was prepared for promoting dye degradation by catalytic ozonation. Via a hydrothermal reaction, highly magnetic manganese ferrite (MnFe2O4) particles were successfully loaded on carbon aerogel (CA) materials (MnFe2O4@CA). The results showed that the developed catalyst strikingly promoted the degradation of dye contaminants by catalytic ozonation, in terms of color removal and reduction of chemical oxidation demand (COD) in rinsing effluents. COD removal efficiency in catalytic ozonation was enhanced by 25% when compared with that achieved by ozonation alone under the same treatment conditions. Moreover, we confirmed that after catalytic ozonation, the rinsing effluents could be recycled to replace fresh water without any evident compromise in the color quality of fabrics. The color difference (ΔEcmc(2:1)) between fabrics treated with recycled effluents and water was not more than 1.0, suggesting that the fabrics treated with recycled effluents displayed acceptable color reproducibility. Although colorfastness and color evenness of fabrics treated with recycled effluents were slightly poorer than those of fabrics treated with water, they were still within the acceptable tolerance. Therefore, the present study validated that catalytic ozonation was a promising technology for saving water and wastewater elimination in textile dyeing. It provides a feasibility assessment of catalytic ozonation for recycling waste effluents to reduce water dependence in textile production. Furthermore, we show a new perspective in on-site recycling waste effluents by catalytic ozonation and enrich the knowledge on feasible approaches for water management in textile production.


Assuntos
Corantes , Ozônio/química , Indústria Têxtil , Águas Residuárias , Purificação da Água , Catálise , Corantes/química , Análise Espectral , Águas Residuárias/química
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