Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 11 de 11
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Environ Technol ; 39(22): 2951-2958, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28838291

RESUMO

Nitrogen-free and nitrogen-doped carbon xerogel materials, from urea and melamine precursors, were prepared at different pH and evaluated as adsorbents/catalysts in the removal of phenol. Then, zero-valent iron (ZVI) was supported on these carbon xerogel materials and its activity was again evaluated for phenol removal by adsorption and catalytic wet peroxide oxidation (CWPO). The prepared samples were characterized by N2 adsorption at -196°C, pH at the point of zero charge (pHPZC) and elemental analysis. The textural properties of the N-free and N-doped carbon xerogels are strongly influenced by pH of the preparation solution and precursor used. The presence of ZVI on all carbon xerogel supports improved the phenol removal efficiency. ZVI supported on urea- and melamine-doped carbon xerogels show a good performance, reaching above 87% phenol conversion after 60 min of CWPO. On the contrary, pure adsorption and CWPO using the same materials without the presence of ZVI gives low phenol removal efficiency. A correlation was found between the activity of ZVI catalysts in CWPO and the N-content of the supports.


Assuntos
Ferro , Fenol , Carbono , Peróxido de Hidrogênio , Nitrogênio , Fenóis
2.
Bioresour Technol ; 214: 404-410, 2016 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-27155795

RESUMO

Although the hydrothermal liquefaction is considered a promising technology for converting microalgae into liquid biofuels, there are still some disadvantages. This paper demonstrated that the bio-oil yield can be significantly improved by adding alcohols as co-solvents and carrying out the conversion at mild conditions (<250°C), but at the expense of a reduced bio-oil quality. By adding ethanol, the bio-oil yields obtained (up to ∼60%) were comparable to the yield obtained at severe operating conditions using only water as solvent (54±2% on average), but the quality of the bio-oil was lower. However, the main advantages of the process here described lie in the utilisation of wet microalgae (∼75% moisture) and alcohol concentrations which avoid both drying the microalgae and decreasing the amount of microalgae loaded in the reactor.


Assuntos
Biocombustíveis , Biotecnologia/métodos , Etanol/metabolismo , Microalgas/metabolismo , Solventes/metabolismo , Temperatura , Água/metabolismo
3.
J Environ Manage ; 177: 240-6, 2016 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-27107392

RESUMO

Several characteristics make Phaeodactylum tricornutum potential candidate for biofuels production such as methane and biodiesel. For this reason, some alternatives are evaluated in this manuscript to improve the conversion of this microalgae into methane. One of these alternatives is the addition of sewage sludge to Phaeodactylum tricornutum for anaerobic co-digestion. Although the co-digestion resulted in lack of synergy, the absence of inhibition indicated that both substrates could be co-digested under certain circumstances, for example if microalgae are cultivated for wastewater treatment purposes. The extraction of lipids using organic solvents has been evaluated for biodiesel production but also as a pre-treatment for anaerobic digestion. The results revealed that the type of solvent influences lipid and biodiesel yields. The high polarity of the mixture methanol/hexane increased the lipid and the biodiesel yields from 10 ± 1 to 53 ± 2 gLipids/100 gVS and from 7 ± 1 to 11 ± 1 gBiodiesel/100 gVS compared with hexane. However, none of these solvents affected the composition of biodiesel. Regarding the methane production after the extraction, it yielded 257 ± 8 and 180 ± 6 mLCH4/gVS from lipid-extracted P. tricornutum using hexane and methanol/hexane respectively. The methane production from the raw microalga was 258 ± 5 mLCH4/gVS in the same experiment. The difference in methane production, mainly after the extraction with methanol/hexane, was a consequence of the changes in the composition of the microalgae after extraction. The extraction did not influence the biodegradability. The ultrasonic pre-treatment prior anaerobic digestion completely disrupted the microalgae cells, but the solubilisation of the organic fraction was scarce (<9.5%). The methane production from pre-treated samples was barely 10-11% higher than the obtained from non pre-treated samples, indicating that the refractory nature of the organic fraction in P. tricornutum is the main obstacle for the methane production.


Assuntos
Biocombustíveis , Microalgas/metabolismo , Anaerobiose , Lipídeos/isolamento & purificação , Metano/biossíntese , Esgotos , Sonicação , Gerenciamento de Resíduos/métodos , Águas Residuárias
4.
Bioresour Technol ; 201: 370-3, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26684667

RESUMO

The aim of this work was to study the effect of the solvent N-methylmorpholine-N-oxide (NMMO) to pre-treat Nannochloropsis oculata before the anaerobic digestion process. The results indicated that the pre-treatment affects the characteristics of the cell wall, which consequently becomes more susceptible to the microorganisms attack during anaerobic digestion. The methane production was increased by 43% after the pre-treatment, from 238±6mLCH4/gVS until 339±4mLCH4/gVS. On the contrary, the methane production from Chlorella vulgaris decreased after the pre-treatment from 251±4mLCH4/gVS to 231±3mLCH4/gVS. The failure on the pre-treatment was attributed to the particular characteristics of the substrate in consequence of a previous drying step.


Assuntos
Biotecnologia/métodos , Óxidos N-Cíclicos/metabolismo , Metano/biossíntese , Microalgas/metabolismo , Morfolinas/metabolismo , Biotecnologia/economia , Chlorella vulgaris/metabolismo , Lipídeos/isolamento & purificação
5.
J Hazard Mater ; 267: 21-30, 2014 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-24413048

RESUMO

This work presents the preliminary study of new carbonaceous materials (CMs) obtained from exhausted sludge, their use in the heterogeneous anaerobic process of biodecolorization of azo dyes and the comparison of their performance with one commercial active carbon. The preparation of carbonaceous materials was conducted through chemical activation and carbonization. Chemical activation was carried out through impregnation of sludge-exhausted materials with ZnCl2 and the activation by means of carbonization at different temperatures (400, 600 and 800°C). Their physicochemical and surface characteristics were also investigated. Sludge based carbonaceous (SBC) materials SBC400, SBC600 and SBC800 present values of 13.0, 111.3 and 202.0m(2)/g of surface area. Biodecolorization levels of 76% were achieved for SBC600 and 86% for SBC800 at space time (τ) of 1.0min, similar to that obtained with commercial activated carbons in the continuous anaerobic up-flow packed bed reactor (UPBR). The experimental data fit well to the first order kinetic model and equilibrium data are well represented by the Langmuir isotherm model. Carbonaceous materials show high level of biodecolorization even at very short space times. Results indicate that carbonaceous materials prepared from sludge-exhausted materials have outstanding textural properties and significant degradation capacity for treating textile effluents.


Assuntos
Compostos Azo/química , Naftalenos/química , Esgotos/análise , Poluentes Químicos da Água/química , Adsorção , Algoritmos , Anaerobiose , Carbono/química , Catálise , Cor , Cinética , Nitrogênio/química , Porosidade , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Termogravimetria , Eliminação de Resíduos Líquidos , Difração de Raios X
6.
J Hazard Mater ; 177(1-3): 990-1000, 2010 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-20092944

RESUMO

In this study, three different approaches for the covalent immobilisation of the horseradish peroxidase (HRP) onto epoxy-activated acrylic polymers (EupergitC) were explored for the first time, direct HRP binding to the polymers via their oxirane groups, HRP binding to the polymers via a spacer made from adipic dihydrazide, and HRP binding to hydrazido polymer surfaces through the enzyme carbohydrate moiety previously modified by periodate oxidation. The periodate-mediated covalent immobilisation of the HRP on hydrazido EupergitC was found to be the most effective method for the preparation of biocatalysts. In this case, a maximum value of the immobilised enzyme activity of 127 U/g(support) was found using an enzyme loading on the support of 35.2mg/g(support). The free and the immobilised HRP were used to study the elimination of phenol in two batch reactors. As expected, the activity of the immobilised enzyme was lower than the activity of the free enzyme. Around 85% of enzyme activity is lost during the immobilisation. However, the reaction using immobilised enzyme showed that it was possible to reach high degrees of phenol removal (around 50%) using about one hundredth of the enzyme used in the soluble form.


Assuntos
Enzimas Imobilizadas/química , Peroxidase do Rábano Silvestre/metabolismo , Fenol/metabolismo , Polímeros/química , Reagentes de Ligações Cruzadas/química , Enzimas Imobilizadas/metabolismo , Métodos , Ácido Periódico/química , Ligação Proteica
7.
Water Sci Technol ; 55(12): 221-7, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17674852

RESUMO

Nowadays, there are increasingly stringent regulations requiring more and more treatment of industrial effluents to generate product waters which could be easily reused or disposed of to the environment without any harmful effects. Therefore, different advanced oxidation processes were investigated as suitable precursors for the biological treatment of industrial effluents containing phenol. Wet air oxidation and Fenton process were tested batch wise, while catalytic wet air oxidation and H2O2-promoted catalytic wet air oxidation processes were studied in a trickle bed reactor, the last two using over activated carbon as catalyst. Effluent characterisation was made by means of substrate conversion (using high liquid performance chromatography), chemical oxygen demand and total organic carbon. Biodegradation parameters (i.e. maximum oxygen uptake rate and oxygen consumption) were obtained from respirometric tests using activated sludge from an urban biological wastewater treatment plant (WWTP). The main goal was to find the proper conditions in terms of biodegradability enhancement, so that these phenolic effluents could be successfully treated in an urban biological WWTP. Results show promising research ways for the development of efficient coupled processes for the treatment of wastewater containing toxic or biologically non-degradable compounds.


Assuntos
Fenóis/química , Fenóis/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo , Purificação da Água/métodos , Peróxido de Hidrogênio/química , Ferro/química , Oxirredução , Temperatura
8.
Insect Biochem Mol Biol ; 32(11): 1525-32, 2002 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12530220

RESUMO

The male Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins (Coleoptera: Scolytidae), produces the bicyclic ketal frontalin as part of a complex semiochemical blend. A key regulated enzyme in the mevalonate pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-R), showed high transcript levels in the anterior midgut of male Jeffrey pine beetles by in situ hybridization. HMG-R expression in this area of the alimentary canal was related to male emergence, where emerged males demonstrated significant up-regulation of HMG-R transcript and pre-emerged males showed only basal levels. Pre-emerged males were induced to express high levels of HMG-R transcript by treatment with juvenile hormone (JH) III. Additionally, isolated anterior midgut tissue from JH III-treated males converted radiolabeled acetate to frontalin, as assayed by radio-HPLC, providing strong evidence that this is the site of frontalin production in male beetles.


Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/metabolismo , Besouros/fisiologia , Fenômenos Fisiológicos do Sistema Digestório , Feromônios/biossíntese , Pinus/parasitologia , Acetatos/metabolismo , Animais , Besouros/anatomia & histologia , Besouros/genética , Especificidade de Órgãos
9.
Insect Biochem Mol Biol ; 30(12): 1203-11, 2000 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11044666

RESUMO

We have isolated a full length 3-hydroxy-3-methylglutaryl coenzyme A synthase (HMG-S) cDNA from the male Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, and studied the effects of topical applications of juvenile hormone III (JH III) on its expression. The predicted translation product of this apparently single copy gene has 63% and 58% identity with HMG-S1 and HMG-S2 from Blattella germanica (L.), and 61% identity with Drosophila melanogaster Hmgs. HMG-S transcript levels remain uniformly low in JH III-treated and control D. jeffreyi females, but are induced approximately 2.5- to 5-fold in JH III-treated males. JH III causes a dose- and time-dependent increase in HMG-S transcripts in the male metathoracic-abdominal region. Since monoterpenoid pheromone precursor synthesis and HMG-CoA reductase expression are under the control of JH III in the metathorax of Ips bark beetles, the observed HMG-S expression pattern suggests that the isoprenoid pathway is similarly important for semiochemical production in D. jeffreyi.


Assuntos
Besouros/enzimologia , Regulação Enzimológica da Expressão Gênica , Hidroximetilglutaril-CoA Sintase/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Besouros/genética , DNA Complementar , Sistema Endócrino/metabolismo , Dosagem de Genes , Humanos , Hidroximetilglutaril-CoA Sintase/isolamento & purificação , Hidroximetilglutaril-CoA Sintase/metabolismo , Masculino , Dados de Sequência Molecular , Homologia de Sequência de Aminoácidos , Distribuição Tecidual , Árvores
10.
J Hazard Mater ; 64(2): 181-93, 1999 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-10337397

RESUMO

Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combinations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma-alumina by pore filling, calcined and later tested. The oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 degrees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducted for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until the end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to the dissolution of the metal oxides from the catalyst surface due to the acidic reaction conditions. Generally, the performance of the catalysts was better when the pH of the feed solution was increased.


Assuntos
Substâncias Perigosas/análise , Metais/química , Óxidos/química , Fenóis/química , Poluentes Químicos da Água/análise , Óxido de Alumínio , Catálise , Cobalto/química , Cobre/química , Compostos Férricos/química , Temperatura Alta , Humanos , Concentração de Íons de Hidrogênio , Compostos de Manganês/química , Oxidantes/química , Oxirredução , Oxigênio/química , Pressão Parcial , Solubilidade , Fatores de Tempo , Óxido de Zinco/química
11.
Acta Cytol ; 19(6): 557-63, 1975.
Artigo em Inglês | MEDLINE | ID: mdl-1061473

RESUMO

A new technique for obtaining endometrial material using the Medhosa Cannula is described. This method is also useful to obtain samples from the endocervix. The Medhosa Cannula is made of flexible plastic. It is 30 cm long and has thin fins on its distal end which, guided by an introduction cone, permit endometrial and endocervical brushing. Six hundred cases are reported. Concomitant histopathological studies were performed in 40 per cent of the patients. There were two false negative cytologic reports (0.88%) and one false positive (6.66%). This is a simple, rapid, innocuous and economical technique, thus fulfilling the prerequisites for routine cytodiagnostic methods. Adequate material was always obtained.


Assuntos
Cateterismo/instrumentação , Colo do Útero/citologia , Endométrio/citologia , Adenocarcinoma/diagnóstico , Adenocarcinoma/patologia , Cateterismo/métodos , Endométrio/patologia , Estudos de Avaliação como Assunto , Feminino , Humanos , Neoplasias do Colo do Útero/diagnóstico , Neoplasias do Colo do Útero/patologia , Neoplasias Uterinas/diagnóstico , Neoplasias Uterinas/patologia , Vagina/citologia , Esfregaço Vaginal/métodos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA