Página 1 dos resultados de 74 itens digitais encontrados em 0.009 segundos

Remoção de Pb2+ e Cr3+ em solução por zeólitas naturais associadas a rochas eruptivas da formação serra geral, bacia sedimentar do Paraná; Removal of Pb2+ and Cr3+ from aqueous solution by natural zeolites associated with eruptive rocks from the serra geral formation, Paraná sedimentary basin

SHINZATO, Mirian Chieko; MONTANHEIRO, Tarcísio José; Janasi, Valdecir de Assis; Andrade, Sandra; Yamamoto, Jorge Kazuo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
66.51%
The capacity of natural zeolites and its host rock (dacite) to remove Pb2+ and Cr3+ from aqueous solutions has been investigated. Results showed that both samples prefer to remove Pb2+ instead of Cr3+. Almost 100% of Pb2+ was removed from solutions with concentration until 50 mg L-1 and 100 mg L-1 of this metal, respectively by dacite and zeolite. The equilibrium of metals adsorption process was reached during the first 30 min by both materials. Na+ can be used to recover Pb2+, but not to remove Cr3+ from the treated samples. The Sips model showed a good fit for experimental data of this study.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Removal of Pb2+ from aqueous solutions using two Brazilian rocks containing zeolites

Shinzato, M. C.; Montanheiro, T. J.; Janasi, Valdecir de Assis; Andrade, S.; Yamamoto, Jorge Kazuo
Fonte: SPRINGER; NEW YORK Publicador: SPRINGER; NEW YORK
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.49%
The removal of Pb2+ from aqueous solution by two Brazilian rocks that contain zeolites-amygdaloidal dacite (ZD) and sandstone (ZS)-was examined by batch experiments. ZD contains mordenite and ZS, stilbite. The effects of contact time, concentration of metal in solution and capacity of Na+ to recover the adsorbed metals were evaluated at room temperature (20A degrees C). The sorption equilibrium was reached in the 30 min of agitation time. Both materials removed 100% of Pb2+ from solutions at concentrations up to 50 mg/L, and at concentrations larger than 100 mg/L of Pb2+, the adsorption capacity of sandstone was more efficient than that of amygdaloidal dacite due to the larger quantities and the type of zeolites (stilbite) in the cement of this rock. All adsorbed Pb2+ was easily replaced by Na+ in both samples. The analysis of the adsorption models using nonlinear regression revealed that the Sips and the Freundlich isotherms provided the best fit for the ZS and ZD experimental data, respectively, indicating the heterogeneous adsorption surfaces of these zeolites.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [03/06259-4]

Adsorção-remoção de íons sulfato e isopropilxantato em zeólita natural funcionalizada

Rodrigues, Cristiane Oliveira
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
36.81%
O presente trabalho descreve estudos relativos à remoção de íons de soluções aquosas via adsorção em zeólitas, apresentando e validando técnicas utilizando zeólitas ativadas, funcionalizadas, saturadas (após acúmulo de poluentes ou contaminantes) e na forma de flocos (ou partículas floculadas), com polímeros floculantes. A modificação de zeólitas naturais pulverizadas foi realizada pela ativação via reação das zeólitas com sais contendo os cátions Na+ seguida de funcionalização com íons Ba+2 e/ou Cu2+, respectivamente. Foram realizados estudos, em escala de bancada, de adsorção de íons sulfato e isopropilxantato (reagente residual da mineração) em materiais ativados e funcionalizados, nas formas floculada e pulverizada. As amostras de zeólita natural (aproximadamente 48 % clinoptilolita e 30 % mordenita) foram preparadas e caracterizadas quanto à distribuição granulométrica (dmédio: 25,4 μm), umidade (2,5 %), porosidade (0,89), área superficial (80 m2.g-1), massa específica (2,2 g.cm-3), potencial zeta, capacidade de troca catiônica (1,08 meq NH4 +.g-1), microestrutura e composição mineralógica. Os resultados obtidos nos estudos de adsorção mostraram que a zeólita natural não apresenta qualquer capacidade de adsorção de íons sulfato e isopropilxantato...

Adsorption of ions onto treated natural zeolite

Rodrigues, Cristiane Oliveira; Rubio, Jorge
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Artigo de Revista Científica Formato: application/pdf
ENG
Relevância na Pesquisa
46.37%
This work presents studies of modification of a natural zeolite by activation with Na+ cations and functionalisation with Ba+2 and/or Cu2+ ions (FZ). The zeolite was characterized, modified and applied in adsorption studies of sulphate and isopropilxanthate ions as flocculated and powdered forms. The reuse of SO4Ba-FZ was investigated by adsorption-removal of either Ba2+ or sulphate ions in stages. Equilibrium data showed that the FZ, flocculated or as powder, provide considerable removal of sulphate ions (qmLangmuir: 1.15 and 1.35 meq.g–1, respectively) and isopropilxanthate (qmLangmuir: 0.35 and 0.93 meq.g-1, respectively). The reuse of the SO4-FZ, either powdered or flocculated also uptake significant amount of Ba2+ or sulphate ions (qmLangmuir: 1.15 meq.g–1), providing a new alternative for the exhausted adsorbent. Thus the activated and functionalised zeolites create new options on the materials engineering area with applications in environmental applied adsorption processes.

Purificação de acido clavulanico utilizando zeolitas.; Purification of clavulanic acid using zeolites.

Marcus Bruno Soares Forte
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/04/2008 PT
Relevância na Pesquisa
36.65%
O presente trabalho teve como objetivo principal a separação e purificação de acido clavulanico a partir de caldo fermentado utilizando zeolitas. Foram utilizadas zeolita natural (ZN) e sintetica faujasita (13X), ambas modificadas por troca ionica com diferentes cations de compensação (Na+1, K+1, Ca+2, Ba+2, Mg+2, Sr+2). Atraves de estudos cineticos de adsorcao de AC, usando as diferentes zeolitas nas respectivas formas cationicas, selecionou-se a zeolita 13X-Na como a mais promissora na adsorcao do referido composto. No equilibrio, houve retencao de 17,4% do AC inicial (CAC*/CAC0 = 0,826) e a quantidade de AC adsorvida, em relacao a quantidade de zeolita (q*) foi 0,4927 mg/g. O diametro médio da molecula de AC (DAC) foi estimado em 9,6 A. A zeolita 13X-Na foi caracterizada em termos de composicao (Si/Al = 1,5), densidade (dz = 2,248 g/cm3), área superficial (SBET = 444,860 m2/g), volume total de poros (Vporos = 0,308 cm3/g), volume de microporos (Vmicro = 0,203 cm3/g) e diâmetro médio de poros (Dporos = 28 A). Através desses resultados, a porosidade da particula calculada foi ?p = 0,69. O leito de particulas de 13X-Na apresentou porosidade ?b = 0,85. Soluções de AC puro foram obtidas através de HPLC em escala semi-preparativa. Isotermas de adsorção nas temperaturas 10...

Comparative study between natural and artificial zeolites as supports for biosorption systems

Tavares, M. T.; Quintelas, C.; Figueiredo, Hugo; Neves, Isabel C.
Fonte: Trans Tech Publications Inc. Publicador: Trans Tech Publications Inc.
Tipo: Artigo de Revista Científica
Publicado em //2006 ENG
Relevância na Pesquisa
56.65%
This study aims the definition of a new material that may act as a robust and yet cost effective biosorbent for treatment of wastewater with low concentration of heavy metals. A comparative study was made between two biosorption systems composed of an Arthrobacter viscosus biofilm supported on Cuban natural zeolites and on prepared NaY and NaX, in terms of their ability to retain ionic chromium. The bacterium is able to reduce Cr(VI) to Cr(III) and, only then, this smaller and positive ion may be entrapped in the zeolite cages by ion exchange. The first support was tested in a continuous flow semipacked bed column. The highest removal ratio, 42%, was achieved for initial chromium concentration of 10 mg/L, but the best up-take, 5.5 mg/gzeolite, was obtained for initial concentration of 70 mg/L. Biosorbents prepared with the same biofilm supported in NaY and NaX zeolites were also considered in batch studies, with a typical kinetics of biosorption processes, reaching 20% of initial chromium removal within an initial range of Cr(VI) concentration between 50 and 250 mg/L. These last structures were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). All these techniques indicated that the biosorption process does not modify the morphology and structure of the FAU-zeolites.; Departamento de Ciências da Terra da Universidade do Minho; La Habana University; Fundação para a Ciência e Tecnologia...

Bacterial biofilm supported on granular activated carbon and on natural zeolites- an application to wastewater treatment

Lameiras, Sandra Raquel de Vasconcelos; Quintelas, C.; Tavares, M. T.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em 22/08/2004 ENG
Relevância na Pesquisa
46.37%
The removal of many heavy metals from industrial wastewater is one of the most important environmental problems to be solved today. The retention of this contaminants by a biofilm supported on granular activated carbon or on natural zeolites is one of the promising technologies for the reduction of this problem, because it is cheap and it removes a broad range of substances, heavy metals and organic compounds. This study aims the development of a system of two mini-columns in series for the removal of chromium (VI) using a biofilm of Arthrobacter viscosus supported on two different materials: granular activated carbon and natural zeolite. The effect of the regeneration of granular activated carbon was also studied.; Ministério da Ciência e Tecnologia. Fundação para a Ciência e Tecnologia (FCT) - POCTI/EQU/12017/2000 , SFRH/BD/8646/2002.

Comparative study between natural and artificial zeolites as supports for biosorption systems

Tavares, M. T.; Quintelas, C.; Figueiredo, Hugo; Neves, Isabel C.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
Publicado em //2005 ENG
Relevância na Pesquisa
56.65%
This study aims the definition of a new material that may act as a robust and yet cost effective biosorbent for treatment of wastewater with low concentration of heavy metals. A comparative study was made between two biosorption systems composed of an Arthrobacter viscosus biofilm supported on Cuban natural zeolites and on prepared NaY and NaX, in terms of their ability to retain ionic chromium. The bacterium is able to reduce Cr(VI) to Cr(III) and, only then, this smaller and positive ion may be entrapped in the zeolite cages by ion exchange. The first support was tested in a continuous flow semi-packed bed column. The highest removal ratio, 42%, was achieved for initial chromium concentration of 10 mg/L, but the best up-take, 5.5 mg/gzeolite, was obtained for initial concentration of 70 mg/L. Biosorbents prepared with the same biofilm supported in NaY and NaX zeolites were also considered in batch studies, with a typical kinetics of biosorption processes, reaching 20% of initial chromium removal within an initial range of Cr(VI) concentration between 50 and 250 mg/L. These last structures were characterized by spectroscopic methods (FTIR and ICP-AES), surface analysis (DRX) and thermal analysis (TGA). All these techniques indicated that the biosorption process does not modify the morphology and structure of the FAU-zeolites.; Fundação para a Ciência e a Tecnologia (FCT) - POCTI/EQU/12017/2001...

Remoção de Pb2+ e Cr3+ em solução por zeólitas naturais associadas a rochas eruptivas da formação serra geral, bacia sedimentar do Paraná

Shinzato,Mirian Chieko; Montanheiro,Tarcísio José; Janasi,Valdecir de Assis; Andrade,Sandra; Yamamoto,Jorge Kazuo
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 PT
Relevância na Pesquisa
46.32%
The capacity of natural zeolites and its host rock (dacite) to remove Pb2+ and Cr3+ from aqueous solutions has been investigated. Results showed that both samples prefer to remove Pb2+ instead of Cr3+. Almost 100% of Pb2+ was removed from solutions with concentration until 50 mg L-1 and 100 mg L-1 of this metal, respectively by dacite and zeolite. The equilibrium of metals adsorption process was reached during the first 30 min by both materials. Na+ can be used to recover Pb2+, but not to remove Cr3+ from the treated samples. The Sips model showed a good fit for experimental data of this study.

Adsorption of ions onto treated natural zeolite

Oliveira,Cristiane da Rosa; Rubio,Jorge
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 EN
Relevância na Pesquisa
46.37%
This work presents studies of modification of a natural zeolite by activation with Na+ cations and functionalisation with Ba+2 and/or Cu2+ ions (FZ). The zeolite was characterized, modified and applied in adsorption studies of sulphate and isopropilxanthate ions as flocculated and powdered forms. The reuse of SO4Ba-FZ was investigated by adsorption-removal of either Ba2+ or sulphate ions in stages. Equilibrium data showed that the FZ, flocculated or as powder, provide considerable removal of sulphate ions (q mLangmuir: 1.15 and 1.35 meq.g-1, respectively) and isopropilxanthate (q mLangmuir: 0.35 and 0.93 meq.g-1, respectively). The reuse of the SO4-FZ, either powdered or flocculated also uptake significant amount of Ba2+ or sulphate ions (q mLangmuir: 1.15 meq.g-1), providing a new alternative for the exhausted adsorbent. Thus the activated and functionalised zeolites create new options on the materials engineering area with applications in environmental applied adsorption processes.

La roca magica: Uses of natural zeolites in agriculture and industry

Mumpton, Frederick A.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 30/03/1999 EN
Relevância na Pesquisa
46.54%
For nearly 200 years since their discovery in 1756, geologists considered the zeolite minerals to occur as fairly large crystals in the vugs and cavities of basalts and other traprock formations. Here, they were prized by mineral collectors, but their small abundance and polymineralic nature defied commercial exploitation. As the synthetic zeolite (molecular sieve) business began to take hold in the late 1950s, huge beds of zeolite-rich sediments, formed by the alteration of volcanic ash (glass) in lake and marine waters, were discovered in the western United States and elsewhere in the world. These beds were found to contain as much as 95% of a single zeolite; they were generally flat-lying and easily mined by surface methods. The properties of these low-cost natural materials mimicked those of many of their synthetic counterparts, and considerable effort has made since that time to develop applications for them based on their unique adsorption, cation-exchange, dehydration–rehydration, and catalytic properties. Natural zeolites (i.e., those found in volcanogenic sedimentary rocks) have been and are being used as building stone, as lightweight aggregate and pozzolans in cements and concretes, as filler in paper...

Natural zeolites chabazite/phillipsite/analcime increase blood levels of antioxidant enzymes

Dogliotti, Giada; Malavazos, Alexis E.; Giacometti, Sonia; Solimene, Umberto; Fanelli, Mauro; Corsi, Massimiliano M.; Dozio, Elena
Fonte: the Society for Free Radical Research Japan Publicador: the Society for Free Radical Research Japan
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.46%
Imbalance between reactive oxygen species generation and antioxidant capacity induces a condition known as oxidative stress which is implicated in numerous pathological processes. In this study we evaluated whether natural zeolites chabazite/phillipsite/analcime may affect the levels of different antioxidant enzymes (gluthatione peroxidase, superoxide dismutase, gluthatione reductase), total antioxidant status and oxidative stress in 25 clinically healthy men, both non-smokers and smokers. Measurements were performed on whole blood or on plasma samples before (T0) and after 4-weeks zeolites intake (T1). At T1, gluthatione peroxidase, superoxide dismutase and gluthatione reductase increased compared to T0 levels, both considering all subjects as joint and after subdivision in non-smokers and smokers. Differently, a reduction in total antioxidant status was observed at T1. Anyway, total antioxidant status resulted higher than the reference values in both groups at each time point. A decrease in lipid peroxidation, a major indicator of oxidative stress assessed by monitoring thiobarbituric acid reactive substances, was also observed in all subjects at T1. Our results suggested that chabazite/phillipsite/analcime may help to counteract oxidative stress in apparently healthy subjects exposed to different oxidative stress risk factors...

Characterization of three natural zeolites.

SOARES, F. S. C.; BERNARDI, A. C. de C.; NOGUEIRA, A. R. de A.
Fonte: In: INTERNATIONAL CONFERENCE ON FOOD AND AGRICULTURE APPLICATIONS OF NANOTECHNOLOGIES, 2010, São pedro, São Pedro: Aptor Software, 2010. Publicador: In: INTERNATIONAL CONFERENCE ON FOOD AND AGRICULTURE APPLICATIONS OF NANOTECHNOLOGIES, 2010, São pedro, São Pedro: Aptor Software, 2010.
Tipo: Resumo em anais de congresso (ALICE) Formato: p. 179
PT_BR
Relevância na Pesquisa
56.88%
In recent years, great attention has been paid to the application of nano structure materials. Since zeolites have primary particles with at least one dimension in the nanometer scale, they may be regarded as nanomaterials of geological and pedological origins. Zeolites are hydrated aluminosilicates, crystalline, with a wide variety of technological applications. Its structure consists of a skeleton with three-dimensional tetrahedral of AlO4 and SiO4, linked via oxygen atoms, and having channels and cavities in which it is possible to settle ions, water molecules or other adsorbates and salts. The Si and Al are at the center of the tetrahedron, the structural frame includes cavities occupied by relatively large sizes cations (Na+, K+, Ca2+, Mg2+) and water molecules, both having considerable freedom of movement, allowing ion exchange and reversible dehydration. High degree of hydration, low density, stability of the crystal structure, cation exchange properties, electrical conductivity, adsorption of gases and catalytic properties are the main properties of zeolites. About forty species of natural zeolites have been identified and over one hundred and fifty species have been synthesized. The synthetic zeolites have a high degree of purity and are widely used as catalysts for the petrochemical industry. In contrast...

Selective catalytic reduction of NO over copper ion-exchanged zeolites / by Kylie Headon.

Headon, Kylie
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 333677 bytes; application/pdf
Publicado em //1999 EN
Relevância na Pesquisa
46.54%
Copper loaded Australian natural zeolites and ZSM-5 zeolites were investigated for the selective catalytic reduction of nitrogen oxides using CH4 and C3h6 with the specific aims of investigating natural zeolite as an alternative support to ZSM-5, determining a rate law for the selective catalytic reduction of nitrogen oxides using C3h6 over Cu-ZSM-5; and, investigating the molecular scale interactions of the reaction gases with Cu-ZSM-5.; Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999; Bibliography: leaves 244-259.; xxii, 259 leaves : ill. ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.

Application of natural zeolites in anaerobic digestion processes: A review

Guerrero, Lorna; Cortés, Isel; de la la Rubia, M. Angeles; Milán, Zhenia; Borja, Rafael; Sánchez, Enrique; Montalvo, Silvio
Fonte: Universidade do Chile Publicador: Universidade do Chile
Tipo: Artículo de revista
EN_US
Relevância na Pesquisa
66.59%
Artículo de publicación ISI; This paper reviews the most relevant uses and applications of zeolites in anaerobic digestion processes. The feasibility of using natural zeolites as support media for the immobilization of microorganisms in different high-rate reactor configurations (fixed bed, fluidized bed, etc.) is also reviewed. Zeolite, with its favorable characteristics for microorganism adhesion, has also been widely used as an ion exchanger for the removal of ammonium in anaerobic digestion due to the presence of Na+, Ca2+ and Mg2+ cations in its crystalline structure. This property is also useful for improving the anaerobic process performances in the treatment of wastewaters with high concentrations of nitrogen compounds, such as cattle, pig and chicken wastes, as it prevents process inhibition. The influence of zeolite particle size and doses in batch mesophilic and thermophilic processes when referring to synthetic or different wastewaters is also reviewed. Finally, the role of zeolite in granulation processes, in anaerobic oxidation processes (Anammox) for promoting the retention of the biomass involved (given its low growth rate), and in hybrid and sequencing reactors such as the moving bed biofilm reactors (MBBR) are also discussed.

The Synthetic Zeolites As Geoinspired Materials

Camblor, Miguel Ángel
Fonte: Sociedad Española de Mineralogía Publicador: Sociedad Española de Mineralogía
Tipo: Artículo Formato: 273443 bytes; application/pdf
ENG
Relevância na Pesquisa
36.49%
Paper based on a Plenary Conference, XXVI Anual Meeting, Sociedad Española de Mineralogía, Oviedo (Asturias), September 2006.; The term geoinspiration was coined by Ruiz-Hitzky to simply denote the wealth of motivation that materials scientists can borrow from the mineral world. Any plausible synthetic strategy affording the preparation of new synthetic materials which, by its own characteristics or by the chemical pathway involved in its synthesis, resemble but do not match materials found in nature, would fit into that concept. The idea parallels that of bioinspiration, and intends to highlight the richness of materials and preparation routes that the synthetic scientist can get by studying, copying and modifying natural materials and processes. My purpose here is to show that over the last half a century zeolite scientists have successfully used a geoinspired approach, avant la lettre, to produce a vast range of new materials with a high impact in the industry and in every day life. While the importance of zeolites as industrial catalysts, adsorbents, active phases for industrial gas separation and purification and detergent builders is easily recognized, other applications closer to the man in the street may pass unnoticed. Two examples are the use of zeolites in double-glazing panels to keep windows clear and transparent and...

High-silica, heulandite-type zeolites prepared by direct synthesis and topotactic condensation

Schmidt, Joel E.; Xie, Dan; Davis, Mark E.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 28/06/2015
Relevância na Pesquisa
36.64%
There are both natural minerals and synthetic zeolites that possess the HEU framework topology. These materials have a limited compositional range (Si/Al < 6), and the natural zeolites often contain a large amount of impurities such as Fe^(3+). The preparation of impurity-free HEU-type zeolites with higher Si/Al ratio could open many areas of application, particularly in catalysis. Here, we report the first high-silica HEU-type zeolite that can be prepared via two different procedures. In the first method high-silica HEU (denoted CIT-8) is prepared using a topotactic condensation mechanism (layered precursor denoted CIT-8P); CIT-8P is obtained from a low-water synthesis in fluoride media. CIT-8 prepared in this manner has a product Si/Al ratio of 9.8 ± 0.7 and a micropore volume of 0.10 cm^3 g^(−1) (measured by nitrogen adsorption). The variable temperature powder X-ray diffraction shows that CIT-8 forms via topotactic condensation from CIT-8P along the b axis. Additionally, high-silica heulandite can be synthesized directly from a hydroxide-mediated reaction mixture (denoted CIT-8H), and has a Si/Al ratio of 6.4 ± 0.3 and a micropore volume of 0.10 cm^3 g^(−1). Both synthesis methods produce zeolites that expand the compositional range of HEU-type zeolites. These synthetic methods allow for the addition of other heteroatoms...

A New Method for Characterization of Natural Zeolites and Organic Nanostructure using Atomic Force Microscopy

Domenico P. R. O. F. Fuoco
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
Relevância na Pesquisa
46.71%
In order to study and develop an economic solution to environmental pollution in water, a wide variety of materials were investigated. Natural zeolites emerge from that research as the best in class of this category. Zeolites are natural materials relatively abundant and non biodegradable, economic and good to perform processes of environmental remediation. This paper contains a full description of a new method to characterize superficial properties of natural zeolites of exotic provenience (Caribbean Islets) with atomic force microscopy (AFM). AFM works with the optical microscope simplicity and the high resolution typical of a transmission electron microscope (TEM). Structural information of mesoporous material is obtained using scanning and transmission electron microscopy (SEM and TEM), only if the sample is conductive, otherwise the sample has to be processed through the grafitation technique, but this procedure induces errors of topography. Therefore, the existing AFM method, to observe zeolite powders, is made in a liquid cell-head scanner, but this work puts in evidence and confirms that it is possible to use an ambient air-head scanner to obtain a new kind of microtopography. Once optimized, this new method allows investigating of organic micelles...

AN INTEGRATED REMEDIATION SYSTEM USING SYNTHETIC AND NATURAL ZEOLITES FOR TREATMENT OF WASTEWATER AND CONTAMINATED SEDIMENTS

RIOS REYES,CARLOS; APPASAMY,DANEN; ROBERTS,CLIVE
Fonte: DYNA Publicador: DYNA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 EN
Relevância na Pesquisa
56.64%
The major sources of water pollution can be classified as municipal, industrial, and agricultural. Different types of polluted aqueous effluents and sediments may be produced, which contain relatively high levels of heavy metals. During the 1990s, the large-scale development of constructed wetlands around the world drew much attention from public and environmental groups. The present study looks at the use of an integrated remediation system using zeolites for the treatment of wastewater and sediments. Zeolites have been widely studied in the past 10 years due to their attractive properties such as molecular-sieving, high cation exchange capacities, and their affinity for heavy metals. Coal industry by-products-based zeolites (faujasite type) have been tested as an effective and low-cost novel alternative for wastewater treatment, particularly their removing of heavy metals. On the other hand, a preliminary laboratory-scale experiment was conducted on the use of natural zeolites (clinoptilolite type) for the retention of heavy metals from canal sediments. Experimental work revealed promising results, which could be replicated on a bigger scale. Although this has been developed for canal sediments, the remediation strategy can be adapted to different waterways such as rivers. The development of the proposed remediation system in a specific experimental site as the major part of an innovation park can provide great benefits to a population living near contaminated effluents. It provides not only opportunities for the mitigation of environmental impact...

Isosteric Heats of Adsorption of N2O and NO on Natural Zeolites

Domínguez,Gerardo; Hernández-Huesca,Rosario; Aguilar-Armenta,Gelacio
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2010 EN
Relevância na Pesquisa
66.51%
We studied the capacities of three natural zeolites to adsorb N2O or NO using a glass high-vacuum volumetric system that permitted characterization of the energetics of the adsorption process. Adsorption equilibrium data were analyzed using the classical Freundlich equation and the Dual-Langmuir model. We employed the Clausius-Clapeyron relationship to calculate the isosteric heats of adsorption using the equilibrium data of the isotherms measured at 273.15 K and 293.15 K. The isosteric heats of reversible adsorption of both gases were smaller than the heats of total adsorption. The interaction energy of N2O with mordenite was larger than the interaction energies of N2O with either erionite or clinoptilolite. The interaction energy of NO was found to be largest with erionite.