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1.
Chemosphere ; 249: 126258, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32213391

RESUMO

Secondary Organic aerosols (SOA) are important components of PM 2.5. In order to control the heavy haze pollution, it is essential to find out the contributions of main SOA precursors. Nowadays, the tracer-based method has been widely used in analyzing the contributions of the precursors to SOA. However, it is not well known that whether the SOA tracers can be oxidized or how the instability of the SOA tracers would influence the accuracy of the tracer-based method for source apportionment. In this paper, the heterogeneous oxidation experiments of SOA tracers produced from isoprene and toluene as well as their mixtures under different conditions were conducted in a 2 m3 indoor chamber. The relative rate constants approach was used to determine the effective rate constants of the ozone reactions of the tracers. Concentrations of 2-Methyl Erythritol, a tracer of isoprene SOA, and 2, 3-Dihydroxy-4-oxopentanoic Acid, a tracer of toluene SOA, were analyzed using GC-MS. The effects of different seed aerosols and initial VOC0/NO on the heterogeneous oxidation of the tracers were investigated. The effects of co-existing components in the SOA produced from the mixture of isoprene and toluene on the heterogeneous oxidation of the tracers by ozone were also studied.


Assuntos
Aerossóis/química , Butadienos/química , Hemiterpenos/química , Ozônio/química , Tolueno/química , Aerossóis/análise , Poluentes Atmosféricos/análise , Oxirredução
2.
Chemosphere ; 249: 126096, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32058131

RESUMO

The importance of strong metal-support interaction (SMSI) in reducible oxide supported noble metal nanoparticles (NP) has been recognized in many thermocatalytic systems but rarely explored in photocatalytic and photothermocatalytic systems. Herein, the promotion effect of SMSI in strontium titanate (STO) supported Pt NP for thermocatalytic, photocatalytic, and photothermocatalytic oxidation (TCO, PCO and PTO) of toluene is reported. SMSI in Pt/STO is achieved through calcination in air (Air-Pt/STO), reduction in H2 atmosphere (H2-Pt/STO), wet reduction in HCHO solution (HCHO-Pt/STO) or NaBH4 solutions (NaBH4-Pt/STO), resulting in the formation of chemisorbed oxygen and negatively charged Pt NP and promoting oxygen activation in TCO and surface plasmon resonance effects of Pt NP in visible-light-induced PCO and PTO. Both TCO and PCO activities go along with the degree of SMSI as Air-Pt/STO > H2-Pt/STO > HCHO-Pt/STO > NaBH4-Pt/STO. Under both visible-light illuminating and thermal environment at 150 °C, the PTO toluene degradation efficiency of Air-Pt/STO is further improved with a factor of 32 times or 9 times than the single PCO or TCO process. The unique synergistic photothermocatalytic oxidation performance of Air-Pt/STO is ascribed to the function of Pt NP and the effect of SMSI. Our findings provide a facile way to design multifunctional supported noble metal catalysts for efficient VOCs degradation process.


Assuntos
Modelos Químicos , Tolueno/química , Catálise , Luz , Nanopartículas Metálicas , Oxirredução , Óxidos , Oxigênio , Estrôncio , Titânio
3.
Inorg Chem ; 59(2): 968-971, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31891256

RESUMO

A dithiolate/hydride bridged Fe-Ni complex, [(CN)(CO)2FeII(µ-pdt)(µ-H)NiII(CN)(PCy3)]- (2, pdt = propane-1,3-dithiolate) has been synthesized by the reaction of [(CN)2(CO)2FeII(pdt)]2- with [NiII(Cl)(H)(PCy3)2] as a synthetic analogue of the Ni-R state of the active site of the [Ni-Fe] hydrogenase. X-ray crystallography of this model complex suggests that the hydride unsymmetrically binds to Ni and Fe similar to natural [Ni-Fe] hydrogenases.


Assuntos
Monóxido de Carbono/química , Complexos de Coordenação/química , Cianetos/química , Hidrogenase/química , Tolueno/análogos & derivados , Monóxido de Carbono/metabolismo , Domínio Catalítico , Complexos de Coordenação/metabolismo , Cianetos/metabolismo , Hidrogenase/metabolismo , Ferro/química , Ferro/metabolismo , Modelos Moleculares , Conformação Molecular , Níquel/química , Níquel/metabolismo , Tolueno/química , Tolueno/metabolismo
4.
Chemosphere ; 247: 125812, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31972483

RESUMO

There emerges an urgent stipulation towards the enhanced toluene catalytic combustion nanocatalysts for whittling down the footprint of toluene, a notorious air pollutant. Unfortunately, Few materials which are currently made accessible both present the high catalytic performance lower than 250 °C and keep durable at elevated temperatures. Herein, we demonstrate an expeditious salt hydrolysis-driven redox-precipitation protocol wherein H+ donated by the hydrolysis of copper salt was used to initiate the regioselective reduction of KMnO4 by H2O2 under controlled redox kinetics in order to assemble the homogeneous mixed solid solution hollow microsphere Cu-Mn-based structure. Manifold characterization technologies unveil that in this unique nanbomicrosphere the abundant microscaled pores are successfully created across Cu-Mn bulks with fine-modulating the chemical properties. In sharp contrast with the compact counterparts without tailed porosity, the tuned crystallinity, accessed edge sites with the unsaturated coordination, fast redox chemistry, and boosted gaseous diffusion during reactions synergize to result in the signally good toluene oxidation, with the complete elimination activity at 252 °C, T90 at 237 °C, and prominent long-term durability under the stringent reaction atmospheres. Our current study ushers in an alternative and tractable arena to excogitate the porous oxide materials for multifarious catalysis implementations.


Assuntos
Microesferas , Tolueno/química , Catálise , Cobre , Peróxido de Hidrogênio , Manganês , Oxirredução , Óxidos/química
5.
J Environ Sci (China) ; 87: 39-48, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31791512

RESUMO

Carbon-silica materials with hierarchical pores consisting of micropores and mesopores were prepared by introducing nanocarbon microspheres derived from biomass sugar into silica gel channels in a hydrothermal environment. The physicochemical properties of the materials were characterized by nitrogen physical adsorption (BET), scanning electron microscopy (SEM), and thermogravimetric (TG), and the adsorption properties of various organic waste gases were investigated. The results showed that microporous carbon materials were introduced successfully into the silica gel channels, thus showing the high adsorption capacity of activated carbon in high humidity organic waste gas, and the high stability and mechanical strength of the silica gel. The dynamic adsorption behavior confirmed that the carbon-silica material had excellent adsorption capacity for different volatile organic compounds (VOCs). Furthermore, the carbon-silica material exhibited excellent desorption characteristics: adsorbed toluene was completely desorbed at 150°C, thereby showing superior regeneration characteristics. Both features were attributed to the formation of hierarchical pores.


Assuntos
Modelos Químicos , Compostos Orgânicos Voláteis/química , Adsorção , Biomassa , Carvão Vegetal , Umidade , Interações Hidrofóbicas e Hidrofílicas , Microesferas , Porosidade , Dióxido de Silício/química , Tolueno/química
6.
Chemosphere ; 240: 124924, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726601

RESUMO

In this work, a 3D computational tomography (CT) of the packing material of a laboratory column biofilter is used to model airflow containing three contaminants. The degradation equations for toluene, formaldehyde and benzo[α]pyrene (BaP), were one-way coupled to the CFD model. Physical validation of the model was attained by comparing pressure drops with experimental measurement, while experimental elimination capacities for the pollutants were used to validate the biodegradation kinetics. The validated model was used to assess the existence of channeling and to predict the impact of the three-dimensional porous geometry on the mass transfer of the contaminants in the gas phase. Our results indicate that a physically meaningful simulation can be obtained using the techniques and approach presented in this work, without the need of performing experiments to obtain macroscopic parameters such as gas-phase axial and radial dispersion coefficients and porosities.


Assuntos
Poluentes Atmosféricos/química , Benzo(a)pireno/química , Formaldeído/química , Tolueno/química , Biodegradação Ambiental , Filtração/métodos , Gases , Tomografia , Tomografia Computadorizada por Raios X
7.
J Environ Sci (China) ; 88: 122-132, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31862054

RESUMO

We used an impregnation method to prepare CuO/AC (activated carbon) composite materials of different CuO content and characterized them via scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), and Fourier transform infrared spectroscopy (FT-IR). The effect of CuO content on toluene adsorption/desorption was evaluated. We explored the reusability of AC and AC03 (CuO modified AC with CuO loading 0.3 wt.%) adsorbents via toluene adsorption/desorption cycle testing. We used quasi-first- and quasi-second-order models, the Bangham model, and the Weber-Morris model to fit the toluene adsorption data. The introduction of CuO species evidently improved the adsorption performance of activated carbon toward toluene. The CuO content markedly affected the specific surface area, CuO dispersal, the numbers of oxygen-containing functional groups on the surface, and adsorption performance of the prepared composite adsorbents. Low CuO content was not favorable for the formation of active adsorption sites, while high content greatly reduced the specific surface area, and even covered active adsorption sites. The toluene adsorption performance varied in the order AC03 > AC02 > AC05 > AC08 > AC01 (AC03, AC02, AC05, AC08 and AC01 are CuO modifying AC with CuO loading 0.3, 0.2, 0.5 0.8 and 0.1 wt.%, respectively). The breakthrough time and toluene adsorption capacity of the AC03 composite adsorbent were 94 min and 701.8 mg/g, respectively, and the recycling efficiency was 92.8% after thermal desorption at 200°C. The adsorption process was best described by the Bangham model and adsorption could be divided into three stages.


Assuntos
Poluentes Atmosféricos/química , Carvão Vegetal , Tolueno/química , Adsorção , Cobre/química , Espectroscopia de Infravermelho com Transformada de Fourier
8.
J Environ Sci (China) ; 88: 260-272, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31862067

RESUMO

In order to study their synergistic catalytic effects in toluene degradation, CuMn2O4/HTS-1 (HTS-1 was a titanium silicon molecular sieve), Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1 catalysts were prepared by the impregnation method. The textural properties, redox properties and acidity of the catalysts were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), frustrated total internal reflection (FT-IR), ammonium temperature-programmed desorption (NH3-TPD) and pyridine adsorption internal reflection (Py-IR) measurements. The potential roles of Lewis acid sites (activating dioxygen) were discussed, and the experimental results indicated that the most efficient route for toluene degradation over Cu0.7Mn2Ce0.3Ox/HTS-1 (toluene conversion rate of 90% (T99)=295°C) was ascribed to regulation of the synergistic effects of redox properties (activating molecular toluene) and Lewis acid sites (activating dioxygen). The Mars-Van-Krevelen (MVK) model was adopted to describe the reaction process of toluene oxidation, which gave an in-depth view into the toluene degradation over CuMn2O4/HTS-1, Cu0.7Mn2Y0.3Ox/HTS-1 and Cu0.7Mn2Ce0.3Ox/HTS-1. In addition, the synergistic effects between redox properties and Lewis acid sites were studied in detail.


Assuntos
Modelos Químicos , Tolueno/química , Catálise , Cobre/química , Manganês/química , Oxirredução , Espectroscopia de Infravermelho com Transformada de Fourier , Titânio
9.
Environ Sci Pollut Res Int ; 27(6): 6052-6065, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31865572

RESUMO

Metal organic frameworks (MOFs) are excellent adsorbents that provide abundant specific surface area, adjustable pore structure, and rich active sites. The purpose of this study was to prepare composites with hydrophobic and high microporous specific surface area and to adsorb toluene gas in moist ambience. An ethanol activation-assisted hydrothermal method was proposed to synthesize copper-benzene-1,3,5-tricarboxylic acid (Cu-BTC) metal-organic framework, Cu-BTC, and ZSM-5 molecular sieve composites (Cu-BTC@ZSM-5). The dynamic adsorption process of toluene on different adsorbents was investigated, and the results showed that the toluene adsorption capacity of Cu-BTC@ZSM-5 (158.6 mg/g) was 2.53 times higher than Cu-BTC (62.7 mg/g), when the ZSM-5 content is 5% and the humidity is 30%RH. Compared with other factors, the humidity inhibited the adsorption of toluene on Cu-BTC@ZSM-5. Langmuir model and the pseudo-second kinetics model can better describe the adsorption behavior of Cu-BTC@ZSM-5. The thermodynamic results showed the adsorption process was a spontaneous exothermic process at low temperature and mainly physical adsorption. The relative regenerability can still up to 80.4% after six cycles. The adsorption mechanisms of Cu-BTC@ZSM-5 were pore-filling adsorption, π-π interaction, cation-π bonding, and hydrophobic interactions. This study will help to design a systematic route to evaluate the adsorption performance of Cu-BTC@ZSM-5 for toluene.


Assuntos
Poluentes Atmosféricos/química , Tolueno/química , Adsorção , Benzeno , Cinética , Modelos Químicos , Termodinâmica
10.
J Chem Phys ; 151(21): 214102, 2019 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-31822083

RESUMO

We propose an enhanced approach to the extrapolation of mean potential forces acting on atoms of solute macromolecules due to their interactions with solvent atoms in complex biochemical liquids. It improves and extends our previous extrapolation schemes by additionally including new techniques such as an exponential scaling transformation of coordinate space with weights complemented by an automatically adjusted balancing between the least square minimization of force deviations and the norm of expansion coefficients in the approximation. The expensive mean potential forces are treated in terms of the three-dimensional reference interaction site model with Kovalenko-Hirata closure molecular theory of solvation. During the dynamics, they are calculated only after every long (outer) time interval, i.e., quite rarely to reduce the computational costs. At much shorter (inner) time steps, these forces are extrapolated on the basis of their outer values. The equations of motion are then solved using a multiple time step integration within an optimized isokinetic Nosé-Hoover chain thermostat. The new approach is applied to molecular dynamics simulations of various systems consisting of solvated organic and biomolecules of different complexity. For example, we consider hydrated alanine dipeptide, asphaltene in toluene solvent, miniprotein 1L2Y, and protein G in aqueous solution. It is shown that in all these cases, the enhanced extrapolation provides much better accuracy of the solvation force approximation than the existing approaches. As a result, it can be used with much larger outer time steps, leading to a significant speedup of the simulations.


Assuntos
Simulação de Dinâmica Molecular , Hidrocarbonetos Policíclicos Aromáticos/química , Proteínas/química , Tolueno/química , Água/química , Solventes/química
11.
Environ Sci Pollut Res Int ; 26(36): 36832-36844, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31745794

RESUMO

A series of Ce-doped LaMnO3 (La1-xCexMnO3) were prepared and were tested for gaseous toluene oxidation in order to investigate the effect of cerium doping in LaMnO3 on activity under photothermal conditions. It was found that the activity and CO2 yield of the catalyst can be effectively increased when x = 0.25. A group of characterization is used to characterize the morphology, composition, and physical properties of the as-prepared catalysts. Results show that the Ce-doped LaMnO3 can form coexistence of La1-xCexMnO3 and CeO2, the reaction of CeO2/La1-xCexMnO3 under photothermal conditions follows the Mars-van Krevelen redox cycle mechanism, and the prepared CeO2/La1-xCexMnO3 can form a highly efficient Z-scheme heterojunction, which can enhance the electrons transfer speed of the catalyst. Moreover, in the photothermal catalytic degradation, lattice oxygen is the most important active substance, a small amount of cerium doping can increase the lattice oxygen content of perovskite and increase the activity of the reaction.


Assuntos
Modelos Químicos , Tolueno/química , Compostos de Cálcio/química , Catálise , Cério/química , Oxirredução , Óxidos/química , Oxigênio , Titânio/química
12.
Chem Commun (Camb) ; 55(83): 12487-12490, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31566647

RESUMO

CF2H-Pseudoprolines obtained from difluoroacetaldehyde hemiacetal and serine are stable proline surrogates. The consequence of the incorporation of the CF2H group is an important decrease of the trans to cis amide bond isomerization energy and a remarkable stabilisation of the cis conformer by an hydrogen bond.


Assuntos
Peptídeos/química , Prolina/análogos & derivados , Tiazóis/química , Tolueno/análogos & derivados , Ligação de Hidrogênio , Metilação , Conformação Molecular , Prolina/química , Estereoisomerismo , Tolueno/química
13.
Molecules ; 24(17)2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31480572

RESUMO

A simple and straightforward synthesis of diporphyrins and pentaporphyrins is reported here. The supramolecular interactions of the new porphyrin derivatives with C60 and PyC60 (a pyridyl [60]fulleropyrrolidine) were evaluated by absorption and fluorescence titrations in toluene. While no measurable modifications of the absorption and fluorescence spectra were observed upon addition of C60 to the porphyrin derivatives, the addition of PyC60 to the corresponding mono-Zn(II) porphyrins resulted in the formation of Zn(porphyrin)-PyC60 coordination complexes and the binding constants were calculated. Results show that the four free-base porphyrin units in pentaporphyrin 6 have a significant contribution in the stabilization of the 6-PyC60 complex. The crystal and molecular features of the pentaporphyrin Zn5 were unveiled using single-crystal X-ray diffraction studies.


Assuntos
Fulerenos/química , Substâncias Macromoleculares/química , Porfirinas/síntese química , Cinética , Substâncias Macromoleculares/síntese química , Modelos Moleculares , Porfirinas/química , Espectrometria de Fluorescência , Tolueno/química
14.
Top Curr Chem (Cham) ; 377(5): 26, 2019 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-31529210

RESUMO

Lignin, one of the main components of lignocellulosic biomass, is the largest renewable source of aromatics on the planet and presents an extraordinary opportunity for being used in the production of bio-based products. It can be transformed for the substitution of aromatic chemical-derived petrol as BTXs. The wide range of applications that it can be obtained from BTXs building blocks makes the selective depolymerization of lignin a great scientific challenge. This review emphasizes the different strategies for the fragmentation of lignin to monomers or aromatics hydrocarbons. Thus, a by-product traditionally discarded or used for energy generation, it could be valorized into high added-value products.


Assuntos
Benzeno/química , Lignina/química , Tolueno/química , Xilenos/química , Líquidos Iônicos/química , Estrutura Molecular , Polimerização
15.
Molecules ; 24(19)2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31554209

RESUMO

A general strategy for preparing shaped toluene methylation catalysts with enhanced para-selectivity and stability is developed by extruding ZSM-5 zeolite with attapulgite as a binder. The novel attapulgite/ZSM-5 extrudate exhibited significantly higher para-selectivity and stability in comparison to the conventional alumina-bound ZSM-5 extrudate. The catalyst samples have been characterized by in situ X-ray diffraction, scanning electron microscope (SEM), NH3 temperature programmed desorption (TPD), thermogravimetric analysis (TGA) as well as n-hexane/cyclohexane physical adsorption. The enhanced catalytic performance of attapulgite/ZSM-5 extrudate is correlated with the in-situ modification of acid sites in the catalyst by mobile alkaline species, which is introduced via extrusion with attapulgite. Moreover, a higher para-selectivity was obtained over attapulgite-bound modified ZSM-5 extrudate. Such facile and universal strategy of extruding ZSM-5 catalysts with attapulgite as binder could pave a way for preparation of shaped zeolite-base catalyst with enhanced catalytic performance.


Assuntos
Tolueno/química , Xilenos/química , Zeolitas/química , Adsorção , Catálise , Compostos de Magnésio/química , Metilação , Compostos de Silício/química , Difração de Raios X
16.
Chemosphere ; 237: 124439, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31376693

RESUMO

Dielectric barrier discharge (DBD) has been widely used as end-of-pipe technology to degrade low-concentration volatile organic compound (VOC) emissions. In this work, the influence of DBD conditions including discharge voltage, VOC residence time in DBD plasma, VOC initial concentration and synergistic effect of multiple VOC mixing on the decomposition efficiency of three VOCs (toluene, ethyl acetate and acetone) were investigated systematically. One focus of this work was to investigate size distribution and chemical composition of aerosol by-products. The results suggested that high discharge voltage, long residence time and low VOC initial concentration would increase VOC removal ratio and their conversion to CO2. Among the three VOCs, toluene was easiest to form particles with a mode diameter between 40 and 100 nm and most difficult to be decomposed completely to CO2. Maximum aerosol yield from toluene was observed to account for 13.1 ±â€¯1.0% of initial concentration (400 ppm) in the condition of discharge voltage 6 kV and residence time 0.52 s. Gas chromatography-mass spectrometry analysis showed that non-nitrogen containing benzene derivatives, nitrophenol derivatives and amines were the main components of toluene aerosol by-products. For ethyl acetate and acetone, aerosols could only be produced in the condition of high discharge voltages (>7.5 kV) and long gas residence time (≥0.95 s) with a bimodal distribution below 20 nm. When the mixture of three VOCs was fed into the plasma, we observed a strong synergistic effect that led to higher VOC removal ratio, but lower conversion of decomposed VOCs to CO2 and aerosols.


Assuntos
Acetatos/química , Acetona/química , Aerossóis/química , Tolueno/química , Compostos Orgânicos Voláteis/química , Dióxido de Carbono/química , Recuperação e Remediação Ambiental/métodos , Cromatografia Gasosa-Espectrometria de Massas , Tamanho da Partícula , Tolueno/análise , Compostos Orgânicos Voláteis/análise
17.
Chemistry ; 25(50): 11641-11645, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31338883

RESUMO

Ibuprofen was prepared from an inactive and inexpensive p-xylene by three-step flow functionalizations through chemoselective metalations of benzyl positions in sequence using an in situ generated LICKOR-type superbase. The flow approach in the microreactor facilitated the comprehensive exploration of over 100 conditions in the first-step reaction by varying concentrations, temperatures, solvents, and equivalents of reagents, enabling optimal conditions to be found with 95 % yield by significantly suppressing the formation of byproducts, followed by the second C-H metalation step in 95 % yield. Moreover, gram-scale synthesis of ibuprofen in the final step was achieved by biphasic flow reaction of solution-phase intermediate with CO2 , isolating 2.3 g for 10 min of operation time.


Assuntos
Ibuprofeno/química , Metais/química , Xilenos/química , Carbono/química , Hidrogênio/química , Ibuprofeno/síntese química , Tolueno/análogos & derivados , Tolueno/química
18.
Molecules ; 24(14)2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31340486

RESUMO

Polyurea (PU) nano-capsules have received voluminous interest in various fields due to their biocompatibility, high mechanical properties, and surface functionality. By incorporating magnetic nanoparticle (MNPs) into the polyurea system, the attributes of both PU and MNPs can be combined. In this work, we describe a facile and quick method for preparing magnetic polyurea nano-capsules. Encapsulation of ionic liquid-modified magnetite nanoparticles (MNPs), with polyurea nano-capsules (PU NCs) having an average size of 5-20 nm was carried out through interfacial polycondensation between amine and isocyanate monomers in inverse nano-emulsion (water-in-oil). The desired magnetic PU NCs were obtained utilizing toluene and triple-distilled water as continuous and dispersed phases respectively, polymeric non-ionic surfactant cetyl polyethyleneglycol/polypropyleneglycol-10/1 dimethicone (ABIL EM 90), diethylenetriamine, ethylenediamine diphenylmethane-4,4'-diisocyanate, and various percentages of the ionic liquid-modified MNPs. High loading of the ionic liquid-modified MNPs up to 11 wt% with respect to the dispersed aqueous phase was encapsulated. The magnetic PU NCs were probed using various analytical instruments including electron microscopy, infrared spectroscopy, X-ray diffraction, and nuclear magnetic spectroscopy. This unequivocally manifested the successful synthesis of core-shell polyurea nano-capsules even without utilizing osmotic pressure agents, and confirmed the presence of high loading of MNPs in the core.


Assuntos
Composição de Medicamentos/métodos , Nanopartículas de Magnetita/química , Nanocápsulas/química , Polímeros/química , DEET/química , Emulsões , Isocianatos/química , Nanopartículas de Magnetita/ultraestrutura , Nanocápsulas/ultraestrutura , Tamanho da Partícula , Poliaminas/química , Polimerização , Tolueno/química , Compostos de Trimetilsilil/química
19.
N Biotechnol ; 53: 41-48, 2019 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-31255711

RESUMO

Microbial electrochemical technologies (MET) are increasingly being considered for in situ remediation of contaminated groundwater. However, their application potential for the simultaneous treatment of complex mixtures of organic and inorganic contaminants, has been only marginally explored. Here we have analyzed the performance of the 'bioelectric well', a previously developed bioelectrochemical reactor configuration, in the treatment of benzene, toluene, ethyl-benzene and xylenes (BTEX) mixtures. Although to different extents, all BTEX were found to be degraded in the bioelectrochemical system, operated using a continuous-flow of groundwater at a hydraulic retention time of 8.8 h, with the graphite anode potentiostatically controlled at +0.200 V vs. the standard hydrogen electrode. In the case of toluene and ethyl-benzene, biodegradation was further confirmed by the GC-MS identification of fumarate-addition metabolites, previously shown to be involved in the activation of these contaminants under anaerobic conditions. Degradation rates were higher for toluene (31.3 ±â€¯1.5 mg/L d) and lower for benzene (6.1 ±â€¯0.3 mg/L d), ethyl-benzene (3.3 ±â€¯0.1 mg/L d), and xylenes (4.5 ±â€¯0.2 mg/L d). BTEX degradation was linked to electric current generation, with coulombic efficiencies falling in the range 53-69%, although methanogenesis also contributed to contaminant degradation. Remarkably, the system also allowed removal of sulfate simultaneously with toluene. Sulfate removal was likely driven by the hydrogen abiotically generated at the cathode. Taken as a whole, these findings highlight the remarkable potential of this innovative reactor configuration for application in a variety of contamination scenarios.


Assuntos
Benzeno/metabolismo , Reatores Biológicos , Técnicas Eletroquímicas , Água Subterrânea/química , Sulfatos/metabolismo , Tolueno/metabolismo , Poluentes Químicos da Água/metabolismo , Xilenos/metabolismo , Benzeno/química , Biodegradação Ambiental , Sulfatos/química , Tolueno/química , Poluentes Químicos da Água/química , Xilenos/química
20.
Chemosphere ; 232: 304-314, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31154192

RESUMO

The fraction of pollutant converted to CO2 versus biomass in biofiltration influences the process efficacy and the lifetime of the bed due to pressure drop increases. This work determined the relative quantitative importance and potential interactions between three critical environmental parameters: toluene concentration (Tol), matric potential (ψ) and temperature (T) on % CO2, elimination capacity (EC) and the production rate of non-CO2 products. These parameters are the most variable in typical biofilter operation. The data was fit to a non-linear model of the form y=a(Tol)bTcψd. A rigorous carbon balance (100.5 ±â€¯7.0%) tracked the fate of degraded toluene as CO2 and non-CO2 carbon endpoints. The % CO2 mineralization varied from (34-91%) with environmental parameters: temperature (20-40 °C), matric potential, (-10 to -100 cmH2O) and residual toluene, (20-180 ppm). The highest conversion to CO2 was at the wettest conditions (-10 cmH2O) and lowest residual toluene concentration (18 ppm). Matric potential had twice the impact of toluene concentration on % CO2, while temperature had less impact. The elimination capacity varied from 11 to 50 gC⋅m-3h-1 and was highest at 40 °C, the wettest conditions with limited impact by toluene concentrations. Temperature increased the EC and non-CO2 production rates strongly while matric potential and toluene concentration had less influence (4x - 10x less). This study illustrated the quantitative significance and simultaneous interaction between critical environmental parameters on carbon endpoints and biofilter performance. This kind of multivariable parameter study provides valuable insights which can address performance and clogging issues in biofilters.


Assuntos
Dióxido de Carbono/química , Matriz Extracelular de Substâncias Poliméricas , Filtração , Tolueno/química , Biodegradação Ambiental , Biomassa , Carbono , Pressão , Solo , Temperatura
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