Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 88
Filtrar
Mais filtros

Medicinas Complementares
Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Chemosphere ; 351: 141261, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38244873

RESUMO

Rapid industrial growth and urbanization have resulted in a significant rise in environmental pollution issues, particularly indoor air pollutants. As a result, it is crucial to design and develop technologies and/or catalysts that are not only cost-effective but also promising high performance and practical applicability. However, achieving this goal has been so far remained a challenging task. Herein, a series of transition metal M - TiO2 (M = W, Fe, Mn) nanocrystals was prepared for photocatalytic degradation of volatile organic compounds (VOCs), i.e., toluene. Of the nanocomposites tested, W-TiO2 showed significantly improved photocatalytic activity for VOC degradation under UV irradiation compared to the others. In particular, the optimized W dopant amount of 0.5 wt% resulted in the outstanding degradation performance of toluene (96%) for the obtained W-TiO2(0.5%) nanocomposite. Moreover, W-TiO2(0.5%) nanocomposite exhibited good stability for 32 h working under high toluene concentration (10 ppm) compared to the pristine TiO2. The current work demonstrates the potential usage of M - TiO2 nanocrystals, particularly W-TiO2(0.5%), as a promising photocatalyst for efficient VOCs degradation.


Assuntos
Poluentes Atmosféricos , Nanocompostos , Titânio/química , Raios Ultravioleta , Tolueno/química , Nanocompostos/química , Catálise , Poluentes Atmosféricos/química
2.
Environ Res ; 215(Pt 3): 114420, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-36167116

RESUMO

Anaerobic degradation is the major pathway for microbial degradation of benzene, toluene, ethylbenzene, and xylenes (BTEX) under electron acceptor lacking conditions. However, how exogenous electron acceptors modulate BTEX degradation through shaping the microbial community structure remains poorly understood. Here, we investigated the effect of various exogenous electron acceptors on BTEX degradation as well as methane production in anaerobic microbiota, which were enriched from the same contaminated soil. It was found that the BTEX degradation capacities of the anaerobic microbiota gradually increased along with the increasing redox potentials of the exogenous electron acceptors supplemented (WE: Without exogenous electron acceptors < SS: Sulfate supplement < FS: Ferric iron supplement < NS: Nitrate supplement), while the complexity of the co-occurring networks (e.g., avgK and links) of the microbiota gradually decreased, showing that microbiota supplemented with higher redox potential electron acceptors were less dependent on the formation of complex microbial interactions to perform BTEX degradation. Microbiota NS showed the highest degrading capacity and the broadest substrate-spectrum for BTEX, and it could metabolize BTEX through multiple modules which not only contained fewer species but also different key microbial taxa (eg. Petrimonas, Achromobacter and Comamonas). Microbiota WE and FS, with the highest methanogenic capacities, shared common core species such as Sedimentibacter, Acetobacterium, Methanobacterium and Smithella/Syntrophus, which cooperated with Geobacter (microbiota WE) or Desulfoprunum (microbiota FS) to perform BTEX degradation and methane production. This study demonstrates that electron acceptors may alter microbial function by reshaping microbial community structure and regulating microbial interactions and provides guidelines for electron acceptor selection for bioremediation of aromatic pollutant-contaminated anaerobic sites.


Assuntos
Poluentes Ambientais , Microbiota , Anaerobiose , Benzeno/química , Derivados de Benzeno , Biodegradação Ambiental , Elétrons , Ferro , Metano , Nitratos/química , Oxidantes , Solo , Sulfatos/química , Tolueno/química , Xilenos
3.
Molecules ; 25(15)2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32707914

RESUMO

The 1,3-benzothiazole (BTZ) ring may offer a valid option for scaffold-hopping from indole derivatives. Several BTZs have clinically relevant roles, mainly as CNS medicines and diagnostic agents, with riluzole being one of the most famous examples. Riluzole is currently the only approved drug to treat amyotrophic lateral sclerosis (ALS) but its efficacy is marginal. Several clinical studies have demonstrated only limited improvements in survival, without benefits to motor function in patients with ALS. Despite significant clinical trial efforts to understand the genetic, epigenetic, and molecular pathways linked to ALS pathophysiology, therapeutic translation has remained disappointingly slow, probably due to the complexity and the heterogeneity of this disease. Many other drugs to tackle ALS have been tested for 20 years without any success. Dexpramipexole is a BTZ structural analog of riluzole and was a great hope for the treatment of ALS. In this review, as an interesting case study in the development of a new medicine to treat ALS, we present the strategy of the development of dexpramipexole, which was one of the most promising drugs against ALS.


Assuntos
Esclerose Lateral Amiotrófica/tratamento farmacológico , Benzotiazóis/síntese química , Fármacos Neuroprotetores/síntese química , Pramipexol/química , Riluzol/química , Animais , Benzotiazóis/química , Benzotiazóis/farmacologia , Ensaios Clínicos como Assunto , Aprovação de Drogas , Avaliação Pré-Clínica de Medicamentos , Humanos , Fármacos Neuroprotetores/farmacologia , Bibliotecas de Moléculas Pequenas/síntese química , Bibliotecas de Moléculas Pequenas/farmacologia , Tolueno/análogos & derivados , Tolueno/química , Resultado do Tratamento
4.
Chemosphere ; 259: 127427, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32599385

RESUMO

Spinel oxides, e.g., NiCo2O4, is a promising catalyst for the catalytic oxidation of toluene. Understanding and designing versatile NiCo2O4 spinel is important for low-temperature toluene oxidation. Here, we investigated the surface-characteristic-dependent degradation activity of NiCo2O4 crystals through experiment and characterization. NiCo2O4 nanosheet using ethanol as solvent (named E--NiCo2O4) exposing {110} crystal planes exhibited the lowest temperature toluene oxidation. The T99 of toluene conversion was 256 °C, which is much lower than that of NiCo2O4 nanosheet using ethylene glycol as solvent (named EG--NiCo2O4), NiCo2O4 octahedron (named O--NiCo2O4) and NiCo2O4 truncated octahedron (named TO--NiCo2O4). Characterization using various techniques such as XRD, TEM, BET, XPS, H2-TPR and CO2-TPD showed that Co3+ and surface adsorbed oxygen (Osur) enriched surface, excellent redox properties and effective diffusion of the reaction product reasonably explain the enhancement in catalytic activity over the E--NiCo2O4. The research reveals that the effect of specific crystal planes and solvent was the key factor to govern the activity of low-temperature toluene oxidation.


Assuntos
Óxido de Alumínio/química , Óxido de Magnésio/química , Tolueno/química , Adsorção , Catálise , Temperatura Baixa , Oxirredução , Óxidos/química , Oxigênio/química , Solventes
5.
Chemosphere ; 258: 127286, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32544811

RESUMO

Micro-capillary bioreactors (1 mm ID, 10 cm long) were investigated for the biodegradation of toluene vapors as a model volatile organic compound (VOC). The intended application is the removal of VOCs from indoor air, when such microbioreactor is coupled with a microconcentrator that intermittently delivers high concentrations of VOCs to the bioreactor for effective treatment. The effects of key operating conditions were investigated. Specifically, gas film and liquid film mass transfer coefficients were determined for different gas and liquid velocities. Both mass transfer coefficients increased with gas or liquid velocity, respectively, and the overall gas-liquid mass transfer was dominated by the liquid-side resistance. Experiments with the microbioreactors focused on the effects of gas velocity, liquid velocity and mineral medium renewal rate on the treatment of toluene vapors at different inlet concentrations. The best performance in terms of toluene removal and mineralization to CO2 was obtained when the gas and liquid velocity ratio was close to one and achieving Taylor or slug flow pattern. Sustained treatment over extended periods of time with toluene elimination capacities ranging from 4000 to over 9000 g m-3 h-1 were obtained, which is orders of magnitude greater than conventional biofilters and biotrickling filters. Biological limitations generally played a more important role than mass transfer limitation. Continuous mineral medium supply at a high rate (10 h liquid retention time) enabled pH control and provided ample nutrient supply and therefore resulted in better toluene elimination and mineralization. Overall, these studies helped select the most suitable conditions for high performance and sustained operation.


Assuntos
Poluentes Atmosféricos/química , Reatores Biológicos , Tolueno/química , Compostos Orgânicos Voláteis/química , Biodegradação Ambiental , Desenho de Equipamento , Gases , Concentração de Íons de Hidrogênio
6.
Chemosphere ; 255: 126930, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402878

RESUMO

Emissions of volatile organic compounds (VOCs) air pollutants could worsen air quality and adversely affect human health, thus developing more efficient low-temperature VOCs removal techniques is desired. A novel continuous system integrating UV-assisted photo-electrochemical catalysis with microbial fuel cell (UV-assisted PEC-MFC) has been established for promoting removal of gaseous ethyl acetate or toluene and generating electricity simultaneously. In this system, CeO2/TiO2/ACF catalytic cathode is prepared and used for combination with bio-anode for accelerating cathodic reaction. This UV-assisted PEC-MFC system exhibits an excellent elimination capacity (EC) of ethyl acetate (∼0.39 g/m3, EC: ∼2.52 g/m3/h) or toluene (∼0.29 g/m3, EC: 1.89 g/m3/h) under close-circuit condition. Furthermore, an outstanding elimination capacity (EC: 28.04 g/m3/h) for high concentration toluene (∼4.10 g/m3) removal is obtained after toluene gas passes sequentially through the catalytic cathode then the bio-anode. This way of PEC degradation and biodegradation, avoids inhibition of exoelectrogens activity from toxicity of high concentration toluene. Simultaneously, the cell voltage of UV-assisted PEC-MFC system is stable at 0.11 V (vs. SCE) and 1.452×10-4 kWh is generated from treatment of toluene gas stream in 6 h duration time. The possible mechanism of VOCs removal in this novel system has been proposed and discussed. This study provides new technical basis for treating gaseous pollutants via integrating photo-electrochemical catalysis with electricity generating microbial fuel cell for energy conversion.


Assuntos
Compostos Orgânicos Voláteis/química , Poluentes Atmosféricos/química , Biodegradação Ambiental , Fontes de Energia Bioelétrica , Catálise , Eletricidade , Eletrodos , Poluentes Ambientais , Gases , Titânio , Tolueno/química , Raios Ultravioleta
7.
Chemosphere ; 251: 126382, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443238

RESUMO

A single metal Pd/γ-Al2O3 catalyst and a bimetallic Pd-Ce/γ-Al2O3 catalyst were prepared by the equal-volume impregnation method to investigate the effect of CeO2 loading on the catalytic oxidation of toluene. The specific surface area, surface morphology, and redox performance of the catalyst were characterized by N2 desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), H2-TPR, O2-TPD, and electron paramagnetic resonance (EPR). The results showed that bimetal catalysts loaded CeO2 had smaller nano-PdO particles than those of the Pd/γ-Al2O3 catalyst. Compared with the catalyst of 0.2Pd/γ-Al2O3 (percentage of mass, the same as below), the catalyst doped with 0.3CeO2 had a stronger reduction peak, which was shifted to the low-temperature zone by more than 80 °C. The results of XPS and O2-TPD showed that the introduction of CeO2 provided more surface oxygen vacancy for the catalyst and enhanced its catalytic oxidation ability, and the amount of desorbed O2 increased from 3.55 µmol/g to 8.54 µmol/g. The results of EPR were that the addition of CeO2 increased the content of active oxygen species and oxygen vacancies on the surface of the catalysts, which might be due to the supply of electrons to the O2 and PdO during the Ce3+toCe4+ conversion process. That could have accelerated the catalytic reaction process. Compared with the single precious metal catalyst, the T10 and T90 of the Pd-Ce/γ-Al2O3 catalyst were decreased by 22 °C and 40 °C, respectively.


Assuntos
Tolueno/química , Óxido de Alumínio/química , Catálise , Cério/química , Chumbo/química , Oxirredução , Oxigênio/química , Espectroscopia Fotoeletrônica
8.
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
9.
Molecules ; 24(11)2019 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-31181870

RESUMO

This study aims at investigating p-menthane, a novel bio-based solvent resulting from the hydrogenation of d-limonene, as a green alternative to n-hexane or toluene for the extraction and solubilization of natural substances. First, conductor-like combination of quantum chemistry (COSMO) coupled with statistical thermodynamics (RS) calculations show a comparable solubilization profile of p-menthane and n-hexane for carotene, volatile monoterpenes such as carvone and limonene, and model triglycerides. Other data obtained experimentally in solid/liquid extraction conditions further indicate that p-menthane showed similar performances to n-hexane for extracting carotenes from carrots, aromas from caraway seeds, and oils from rapeseeds, as these products showed a comparable composition. p-Menthane was also tested using common analytical extraction procedures such as Soxhlet for determination of oil content via multiple extraction stages, and Dean-Stark for determination of water content via azeotropic distillation. For both systems, yields were comparable, but for Dean-Stark, the distillation curve slope was higher when using p-menthane, and the time needed to attain 100% water recovery was 55% shorter than for toluene. Taken together, these results reveal the potential of p-menthane as a green replacer for petroleum-based solvents such as n-hexane or toluene.


Assuntos
Produtos Biológicos/química , Citrus sinensis/química , Química Verde/métodos , Mentol/química , Solventes/química , Carotenoides/isolamento & purificação , Carum/química , Daucus carota/química , Destilação , Ácidos Graxos/análise , Cinética , Odorantes/análise , Óleo de Brassica napus , Sementes/química , Solubilidade , Tolueno/química , Água/química
10.
Toxicol In Vitro ; 58: 110-117, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30910524

RESUMO

Toxicity of toluene and by-products formed during its catalytic oxidative degradation was studied in human bronchial BEAS-2B cells repeatedly exposed. BEAS-2B cells were exposed using an Air-Liquid Interface (ALI) System (Vitrocell®) for 1 h per day during 1, 3 or 5 days to gaseous flows: toluene vapors (100 and 1000 ppm) and outflow after catalytic oxidation of toluene (10 and 100%). After exposure to gaseous flow, cytotoxicity, inflammatory response and Xenobiotic Metabolism Enzymes (XME) gene expression were investigated. No significant cytotoxicity was found after 5 days for every condition of exposure. After cells exposure to catalytic oxidation flow, IL-6 level increased no significantly in a time- and dose-dependent way, while an inverted U-shaped profile of IL-8 secretion was observed. XME genes induction, notably CYP2E1 and CYP2F1 results were in line with the presence of unconverted toluene and benzene formed as a by-product, detected by analytical methods. Exposure to pure toluene also demonstrated the activation of these XMEs involved in its metabolism. Repeated exposure permits to show CYP1A1, CYP1B1 and CY2S1 expression, probably related to the formation of other by-products, as PAHs, not detected by standard analytical methods used for the development of catalysts.


Assuntos
Poluentes Atmosféricos/toxicidade , Tolueno/toxicidade , Poluentes Atmosféricos/química , Óxido de Alumínio/química , Catálise , Técnicas de Cultura de Células , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Cobalto/química , Sistema Enzimático do Citocromo P-450/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Resíduos Industriais , Interleucina-6/metabolismo , Interleucina-8/metabolismo , Oxirredução , Tolueno/química , Compostos Orgânicos Voláteis/química , Compostos Orgânicos Voláteis/toxicidade
11.
J Appl Biomater Funct Mater ; 17(1): 2280800018809917, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30803278

RESUMO

BACKGROUND:: Encapsulation is one of the methods used to trap active ingredients in the wall material of microparticles. AIM:: The aim of this study was to evaluate the encapsulation of red ginger oleoresin using an emulsion crosslinking method with chitosan as the wall material. METHODS:: Emulsions were formed of red ginger oleoresin with chitosan in concentrations of 1%, 2%, 3%, and 4% (w/v), respectively. The emulsions were then mixed with corn oil and stirred for one hour to obtain a second set of emulsions, and glutaraldehyde saturated toluene (GST) was added dropwise in quantities of 20, 10, 6.7, and 5 ml, respectively. This was followed by the addition of 2 ml of 25% glutaraldehyde and the emulsions were stirred for two hours. The resulting microcapsules were washed with petroleum ether followed by hexane and then dried in an oven at 70oC. RESULTS:: The emulsion crosslinking method used to trap the red ginger oleoresin in chitosan produced microcapsules of good spherical geometry with the mean diameter ranging from 75.61 ± 11.8 µm to 178.65 ± 40.7 µm. The highest yield was 98.93% and encapsulation efficiency was 83.1%. Thermogravimetric and differential thermal analysis showed that the melting point was at a temperature between 120 and 130oC. CONCLUSION:: Chitosan concentration has little effect on encapsulation yield, whereas the amount of GST tends to strengthen the crosslinking bonds of chitosan and reduces the mean diameter of microspheres.


Assuntos
Cápsulas/química , Quitosana/química , Emulsões/química , Extratos Vegetais/química , Zingiber officinale/química , Reagentes de Ligações Cruzadas/química , Cromatografia Gasosa-Espectrometria de Massas , Zingiber officinale/metabolismo , Glutaral/química , Termogravimetria , Tolueno/química , Temperatura de Transição
12.
Environ Monit Assess ; 190(9): 560, 2018 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-30159642

RESUMO

Ozone and a Fe2+/TiO2-based catalyst were examined in the degradation of a synthetic solution of benzene toluene and xylene (BTX) in an advanced oxidation process (AOP). The catalyst beads were made from the slurry waste of aluminum production process, by inserting the TiO2 content and subsequent calcination. The reduction of the BTX concentration load was monitored by the reduction of chemical oxygen demand (COD) and BTX concentration. Different levels were used on factors: pH, time of treatment, initial concentration of BTX, and percentage of TiO2. The process was conducted in a bubble column reactor with the insertion of catalyst beads. A response surface methodology technique (CCD) was used to build a model based on COD reduction results. The model was optimized using the normal-boundary intersection (NBI) algorithm to maximize COD reduction and minimize the variance attributed to the process. Optimization led to COD reductions of 80% in 2 h of experiment. Correlation analysis of coefficient models from experimental data R2adj was 0.9966, showing a good fit of model data. In the optimized conditions, the possible increase of the biodegradability ratio of the BTX solution, through the biochemical oxygen demand (BOD) and COD, was also analyzed. Under pre-treatment conditions, the BOD/COD ratio was 0.13. After the treatment, it increased to 0.56. Graphical abstract ᅟ.


Assuntos
Benzeno/química , Sedimentos Geológicos/química , Ozônio/química , Titânio/química , Tolueno/química , Eliminação de Resíduos Líquidos/métodos , Xilenos/química , Algoritmos , Alumínio , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Catálise , Monitoramento Ambiental , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Indústria Manufatureira , Oxirredução , Soluções
13.
Environ Toxicol Chem ; 37(3): 729-737, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29044663

RESUMO

The formation of toluene by microbiological processes can confound environmental investigations relating to petroleum releases. This is because toluene is a constituent of petroleum and can move readily within wetland environments, and analysis for toluene in relation to a petroleum release can lead to incorrect assignment of detected biogenic toluene as related to the release. No legally defensible method of distinguishing biogenic and petrogenic origins of detectible concentrations of toluene have been demonstrated to date. Using example petrogenic samples and samples of peat from 2 wetland environments, a poor bog and a poor fen, the present study demonstrates the use of an established ASTM International analytical methodology that was originally designed for arson analysis for the determination of the origin of toluene. Environmental forensic data-interpretation methods such as chromatogram inspection and diagnostic ratios are shown to be capable of readily distinguishing biogenic and petrogenic origins of toluene. Environ Toxicol Chem 2018;37:729-737. © 2017 SETAC.


Assuntos
Poluentes Ambientais/análise , Ciências Forenses , Tolueno/análise , Carvão Vegetal/química , Petróleo/análise , Solo , Tolueno/química , Áreas Alagadas
14.
J Environ Manage ; 204(Pt 1): 291-299, 2017 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-28898750

RESUMO

This study was conducted to quantify and rank the effectiveness of onsite exsitu remediation by enhanced natural attenuation using soil quality index. The investigation was conducted at three oil spill sites in the Niger Delta (5.317°N, 6.467°E), Nigeria with a predominance of Oxisols. Baseline assessment and a two-step post-remediation monitoring of the sites were conducted. Target contaminants including total petroleum hydrocarbon (TPH) and BTEX (benzene, toluene, ethylbenzene, and xylene) were analyzed by gas chromatography-mass spectrometry. Results of the baseline assessment showed that TPH concentrations across the study sites averaged between 5113 and 7640 mg/kg at 0- to 1-m depth, which was higher than the local regulatory value of 5000 mg/kg. The soil quality index across the sites ranged between 68 and 45, suggesting medium to high potential ecological health risks with medium to high priority for remediation. BTEX concentrations followed a similar trend. However, after remediation TPH degraded rapidly initially and then slowly but asymptotically during the post-remediation monitoring period. Then, soil quality index across the study sites ranged between 100 and 58, indicating very low to medium potential ecological health risks. This demonstrates the effectiveness of onsite exsitu remediation by enhanced natural attenuation as a remediation strategy for petroleum-contaminated soils, which holds great promise for the Niger Delta province.


Assuntos
Derivados de Benzeno/química , Benzeno/química , Poluição Ambiental/análise , Hidrocarbonetos/química , Poluição por Petróleo/análise , Petróleo/análise , Solo/química , Tolueno/química , Xilenos/química , Níger , Nigéria
15.
Environ Sci Pollut Res Int ; 24(26): 20922-20933, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28721623

RESUMO

The effect of dissolved organic matter (DOM) and oil on the removal of the water-soluble compounds benzene, toluene, ethylbenzene, and xylene isomers (BTEX) by two low-cost biosorbents Macrocystis pyrifera and Ulva expansa) was evaluated. DOM decreased the adsorption capacity of toluene, ethylbenzene, and xylenes of the two biosorbents. In contrast, the removal of benzene increased under the same conditions in single and multi-solute systems: this effect was dominant in U. expansa biomass treatments. In the presence of DOM and oil in solutions, the removal of BTEX notoriously increased, being oil that contributed the most. Solubility and hydrophobicity of pollutants played a key role in the adsorption process. The attractions between BTEX molecules and biosorbents were governed by π-π and hydrophobic interactions. Affinities of biosorbents for BTEX were mainly in the order of X > E > T > B. The Langmuir and Sips equations adjusted the adsorption isotherms for BTEX biosorption in deionized and natural water samples, but in the case of oily systems, the Freundlich equation seemed to have a better fit. The biosorption processes followed a pseudo-second-order rate in all the cases.


Assuntos
Benzeno/química , Alga Marinha/metabolismo , Tolueno/química , Xilenos/química , Adsorção , Derivados de Benzeno/química , Biomassa , Isomerismo , Compostos Orgânicos/química , Petróleo/metabolismo , Solubilidade , Soluções , Ulva/metabolismo
16.
IET Nanobiotechnol ; 11(3): 310-316, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28476989

RESUMO

A green route for the synthesis of palladium (Pd) nanoparticles (Pd NPs) employing Poplar leaf extract as a reducing and capping agent is described. The as-prepared Pd NPs are spherical with a face centred cubic structure, a particle distribution of 2.2-6.8 nm and an average particle size of 4.2 nm. The application of this catalyst toward homogeneous Suzuki coupling reactions was investigated. The Pd NPs afforded a yield of 98.86% in the Suzuki coupling reaction of 4-bromotoluene with phenylboronic acid using 0.01 mmol% of the catalyst at 60°C for 30 min under an air atmosphere.


Assuntos
Ácidos Borônicos/química , Nanopartículas Metálicas/química , Paládio/química , Extratos Vegetais/química , Folhas de Planta/química , Populus/química , Tolueno/análogos & derivados , Produtos Biológicos/química , Química Verde/métodos , Teste de Materiais , Nanopartículas Metálicas/ultraestrutura , Tamanho da Partícula , Tolueno/química
17.
Appl Microbiol Biotechnol ; 101(8): 3451-3462, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28062975

RESUMO

Biotrickling filters (BTFs) are often subjected to transient-state operation due to different variations in the operation of industrial-scale sources of pollution. In this research, performance of a laboratory-scale BTF packed with pall ring and pumice (1:1 v/v) and inoculated with Ralstonia eutropha was evaluated for the treatment of toluene vapor under various transient conditions. The experiments were performed at empty bed residence times (EBRTs) of 45 and 90 s and toluene inlet concentration in the range of 0.5-4 g m-3. The transient-state experiments consisted of a sudden increase in inlet gas concentration, sudden change of trickling liquid rate, intermittent loading for 10 h day-1, aeration without toluene loading during shutdown periods, and long-term starvation. The maximum elimination capacity (ECmax) was 280 g m-3 h-1 under continuous loading. The removal efficiency (RE) reached 90 % in intermittent loading experiments at toluene inlet concentration of 3 g m-3 in less than 1 h after loading initiation. RE dropped to 50 % due to 4.5-fold increase in the inlet loading rate (ILR) during shock load experiment. The system became completely active after 24 h, when the BTF was subjected to a long-term starvation period for 7 days. The results showed that aeration at non-toluene loading periods could improve the BTF performance under intermittent loading condition.


Assuntos
Filtração/métodos , Gases/análise , Tolueno/química , Poluentes Atmosféricos , Biodegradação Ambiental , Reatores Biológicos , Cupriavidus necator/metabolismo , Compostos Orgânicos Voláteis
18.
Chemosphere ; 169: 678-684, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27912192

RESUMO

Groundwater fluctuation is often overlooked and lack of study in the field contaminant hydrogeology. Hydraulic force from fluctuating groundwater tables leads to dissolution and subsequent enhanced advective transport of petroleum (e.g. BTEX) in contaminated subsurface system. A laboratory investigation of effect of the groundwater table fluctuation (GTF) on BTEX transport, taking toluene as a typical compound, in a typical representative model of aquifers subjected to a daily water-table fluctuation was undertaken in this work. Results showed that toluene in effluent degraded significantly with cycles of GTF, and the attenuation rates differed in porous media types with higher value for fine-coarse sand media (13.7 mg L-1 d-1) and lower for fine sand-clay media (2.8 mg L d-1). Hydraulic and hydrochemical evidences inferred that toluene attenuation was controlled mainly by flushing effect in the initial GTF cycle stages, followed by dissolution and mixing action in the later stages. Meanwhile, adsorption was found to take effects in toluene behavior throughout the whole GTF process, particularly obvious in fine sand-clay media with its toluene attenuation rate of only 2.8 mg L d-1.


Assuntos
Sedimentos Geológicos/química , Água Subterrânea/química , Modelos Teóricos , Petróleo/análise , Tolueno/análise , Poluentes Químicos da Água/análise , Adsorção , Porosidade , Solubilidade , Propriedades de Superfície , Tolueno/química , Movimentos da Água , Poluentes Químicos da Água/química
19.
Environ Res ; 152: 328-335, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27837714

RESUMO

Toluene is one of the most used Volatile Organic Compounds (VOCs) in the industry despite its major health impacts. Catalytic oxidation represents an efficient remediation technique in order to reduce its emission directly at the source, but it can release by-products. To complete the classical performance assessment using dedicated analytical chemistry methods, we propose to perform an untargeted toxicological validation on two efficient catalysts. Using biological system allows integrating synergy and antagonism in toxic effects of emitted VOCs and by-products, often described in case of multi-exposure condition. Catalysts Pd/α-Al2O3 and Pd/γ-Al2O3 developed for the oxidation of toluene were both coupled to a Vitrocell® Air-Liquid Interface (ALI) system, for exposure of human A549 lung cells during 1h to toluene or to catalysts exhaust before quantification of xenobiotics metabolizing enzymes. This study validated initially the Vitrocell® as an innovative, direct and dynamic model of ALI exposure in the assessment of the performances of new catalysts, showing the presence of chemically undetected by-products. The comparison of the two catalysts showed then that fewer organic compounds metabolizing genes were induced by Pd/γ-Al2O3 in comparison to Pd/α-Al2O3, suggesting that Pd/γ-Al2O3 is more efficient for toluene total oxidation from a toxicological point of view.


Assuntos
Óxido de Alumínio/química , Catálise , Poluentes Ambientais/química , Recuperação e Remediação Ambiental/métodos , Paládio/química , Tolueno/química , Recuperação e Remediação Ambiental/instrumentação , Oxirredução , Compostos Orgânicos Voláteis/química
20.
ChemSusChem ; 9(24): 3434-3440, 2016 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-27885809

RESUMO

Toluene is a basic chemical that is currently produced from petroleum resources. In this paper, we report a new route for the effective synthesis of toluene from isoprene and acrolein, two reactants readily available from biomass, through a simple two-step reaction. The process includes Diels-Alder cycloaddition of isoprene and acrolein in a Zn-containing ionic liquid at room temperature to produce methylcyclohex-3-enecarbaldehydes (MCHCAs) as intermediates, followed by M (M=Pt, Pd, Rh)/Al2 O3 -catalyzed consecutive dehydrogenation-decarbonylation of the MCHCAs at 573 K to generate toluene with an overall yield up to 90.7 %. Model reactions indicated that a synergistic inductive effect of the C=C double bond and the aldehyde group in MCHCA plays a key role in initiating the consecutive dehydrogenation-decarbonylation, and that methyl benzaldehydes are the key intermediates in the gas-phase transformation of MCHCAs. Microcalorimetric adsorption of CO on different catalysts showed that decarbonylation of the substrate occurs more likely on the strong adsorption sites. To the best of our knowledge, it is the first report of Pt/Al2 O3 -catalyzed consecutive dehydrogenation-decarbonylation of a given compound in one reactor. This work provides a highly efficient and environmental friendly route to toluene by utilizing two compounds that can be prepared from biomass.


Assuntos
Acroleína/química , Biomassa , Butadienos/química , Hemiterpenos/química , Pentanos/química , Tolueno/química , Adsorção , Óxido de Alumínio/química , Catálise , Química Verde , Platina/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA