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1.
Environ Sci Pollut Res Int ; 24(4): 4077-4092, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27933495

RESUMO

Magnetic cerium-doped mesoporous titanium dioxide was synthesized by combining sol-gel method and calcination using tetrabutanate and ammonium cerium nitrate as precursors and Pluronic P123 as a template coating on iron oxide covered with carbon in ethanol. The magnetic Ce-doped catalyst showed only anatase structure with a slight increase in lattice parameters compared to the undoped catalyst. The Ce LIII-edge X-ray absorption near-edge spectroscopy (XANES) spectra showed Ce3+, and the cerium substitution doping into titanium dioxide was proposed. Degradation of S-metolachlor in aqueous magnetic photocatalyst suspension followed (pseudo) first-order kinetics in the presence of 0.5 g L-1 of γ-Fe2O3@C@0.16 mol% Ce-mTiO2 with a half-life of 55.18 ± 1.63 min. Fifteen degradation products were identified, and their transformation routes of the photocatalytic degradation were then proposed. Complementary toxicity assessment of the treated S-metolachlor solution was undertaken with Environment Canada's algal microplate assay measuring growth inhibition (72-h IC50) in the freshwater chlorophyte Pseudokirchneriella subcapitata. This test method revealed a significant decrease in toxicity (1.7-fold reduction after 180 min of irradiation treatment), thereby confirming that the by-products formed following photocatalysis would be less harmful from an environmental point of view. Photocatalytic degradation of S-metolachlor thus appears to hold promise as a cost-effective treatment technology to diminish the presence of this herbicide in aquatic systems.


Assuntos
Acetamidas/química , Cério/química , Titânio/química , Catálise , Meia-Vida , Luz , Campos Magnéticos , Processos Fotoquímicos
2.
J Hazard Mater ; 190(1-3): 930-7, 2011 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-21546159

RESUMO

The TiO(2) modified with nanosized gold particles was prepared by deposition-precipitation at pH 7 and calcination in air at various temperatures up to 973 K. The materials were characterized by transmission electron microscope, X-ray diffraction spectrometry, and atomic absorption spectroscopy. The highest photocatalytic efficiency was obtained at the calcination temperature of 873 K. The decrease in 3,4-dichlorophenylurea concentration follows first order kinetics with a half life of 36.6 ± 2.0 min in 100 mg L(-1) of 0.83 wt% Au/TiO(2). Fifteen degradation products were identified using LC/MS/MS and IC. Degradation pathway was proposed on the basis of the observed transformation products.


Assuntos
Nanopartículas Metálicas/química , Compostos de Fenilureia/química , Fotólise , Luz Solar , Titânio/química , Catálise , Ouro , Meia-Vida , Cinética , Compostos de Fenilureia/efeitos da radiação , Fotólise/efeitos dos fármacos , Fotólise/efeitos da radiação , Suspensões , Espectrometria de Massas em Tandem
3.
J Hazard Mater ; 146(1-2): 204-13, 2007 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-17215079

RESUMO

The photocatalytic degradation of triazophos in aqueous TiO2 suspension has been studied in a photoreactor operating with simulated solar radiation. The decrease in triazophos concentration followed first-order kinetics with a half-life of 4.76+/-0.42 h at a TiO2 suspension concentration of 10 mg/L. Seventeen degradation products were identified using HPLC-UV, HPLC/MS/MS, GC/MS/MS and IC, and by comparing retention times and spectra with commercially available authentic standards. On the basis of the observed transformation products, two routes were proposed, one based on the initial oxidative cleavage of PS bond to PO bond, and the other on initial cleavage of the ester P-O bonds. Photocatalysis holds promise for the solar treatment of pesticide-contaminated waters.


Assuntos
Organotiofosfatos/química , Organotiofosfatos/efeitos da radiação , Triazóis/química , Triazóis/efeitos da radiação , Poluentes Químicos da Água/química , Poluentes Químicos da Água/efeitos da radiação , Catálise , Inseticidas/química , Inseticidas/efeitos da radiação , Fotoquímica , Luz Solar , Titânio/química , Purificação da Água/métodos
4.
Anal Bioanal Chem ; 384(5): 1236-45, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16432722

RESUMO

A confirmatory method for the determination of organochlorine pesticides (OCPs) and their metabolites (endrin, alpha-endosulfan, beta-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide, 2,4'-DDD, 4,4'-DDD, 2,4'-DDE 4,4'-DDE, 2,4'-DDT, and 4,4'-DDT) in surface waters using liquid chromatography /APCI/tandem mass spectrometry has been developed. Chromatographic separation was carried out on a ChromSpher 5 Pesticide column using a gradient elution with mobile phase 1mM ammonium acetate-acetonitrile. Endrin, alpha-endosulfan, beta-endosulfan , endosulfan sulfate, heptachlor and heptachlor epoxide were determined in the negative ionization mode, while the rest compounds in positive ionization mode. For the identification of the analytes, two multireaction monitoring transitions were selected per compounds except for the heptachlor which selected ion monitoring was used. The linearity of the optimized method ranges after SPE concentration, from 0.009 to 30.60 microgL(-1) with correlation coefficients greater than 0.99. The method recovery values varied from 72 to 119 % for the different fortification levels . The developed method was successfully applied to determine OCPs and their metabolites in surface water samples collected near paddy fields in growing season of rice, at year 2005 in Pathumthani province, Thailand. Endosulfan sulfate was detected in five out of seven samples and three of them could be quantitated in the range of 0.31 to 0.50 microgL(-1).


Assuntos
Água Doce/química , Hidrocarbonetos Clorados/análise , Resíduos de Praguicidas/análise , Espectrometria de Massas em Tandem/métodos , Cromatografia Líquida/instrumentação , Cromatografia Líquida/métodos , Conformação Molecular , Sensibilidade e Especificidade , Estereoisomerismo , Propriedades de Superfície , Espectrometria de Massas em Tandem/instrumentação
5.
Anal Bioanal Chem ; 381(1): 268-76, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15696272

RESUMO

A confirmation method for the determination of 18 aromatic amines originating from azo dyes after reductive cleavage was developed. The method is based on the use of high-performance liquid chromatography/tandem mass spectrometry with atmospheric-pressure chemical ionization. For the identification of the analytes one precursor ion and two daughter ions (multi-reaction monitoring, MRM) were selected and the LC-MS/MS parameters optimized to obtain high sensitivity and selectivity. The linear ranges varied from 0.1-1 to 30-50 microg mL(-1) with correlation coefficients of 0.99 or better. The applicability of the method to determine o-tolidine (3,3'-dimethylbenzidine) and 3,3'-dimethoxybenzidine in textiles following reductive cleavage of acid red 114, trypan blue, and Chicago sky blue 6B was demonstrated.

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