Quintero K.,Central University of Venezuela |
Martinez M.,Central University of Venezuela |
Hackley P.,U.S. Geological Survey |
Marquez G.,University of Huelva |
And 3 more authors.
Energy Sources, Part A: Recovery, Utilization and Environmental Effects | Year: 2011
The aim of this work was to carry out a geochemical study of channel samples collected from six coal beds in the Marcelina Formation (Zulia State, western Venezuela) and to determine experimentally the gas content of the coals from the Paso Diablo mine. Organic geochemical analyses by gas chromatography-mass spectrometry and isotopic analyses on-line in coalbed gas samples were performed. The results suggest that the Guasare coals were deposited in a continental environment under highly dysoxic and low salinity conditions. The non-detection of 18α(H)-oleanane does not preclude that the organic facies that gave rise to the coals were dominated by angiosperms. In addition, the presence of the sesquiterpenoid cadalene may indicate the subordinate contribution of gymnosperms (conifers) in the Paleocene Guasare mire. The average coalbed gas content obtained was 0.6 cm 3/g. δ 13C and D values indicate that thermogenic gas is prevalent in the studied coals. Copyright © Taylor & Francis Group, LLC.
Briceno S.,Venezuelan Institute for Scientific Research |
Bramer-Escamilla W.,Venezuelan Institute for Scientific Research |
Silva P.,Venezuelan Institute for Scientific Research |
Garcia J.,University of Los Andes, Venezuela |
And 6 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2014
Nickel ferrite (NiFe2O4) was supported on activated carbon (AC) from petroleum coke (petcoke). Potassium hydroxide (KOH) was employed with petcoke to produce activated carbon. NiFe2O4 were synthesized using PEG-Oleic acid assisted hydrothermal method. The structural and magnetic properties were determined using thermogravimetric and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), Fourier Transform Infrared (IR-FT), surface area (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). XRD analysis revealed the cubic spinel structure and ferrite phase with high crystallinity. IR-FT studies showed that chemical modification promoted the formation of surface oxygen functionalities. Morphological investigation by SEM showed conglomerates of spherical nanoparticles with an average particle size of 72 nm and TEM showed the formation of NiFe2O4/carbon nanofibers. Chemical modification and activation temperature of 800 C prior to activation dramatically increased the BET surface area of the resulting activated carbon to 842.4 m2/g while the sulfur content was reduced from 6 to 1%. Magnetic properties of nanoparticles show strong dependence on the particle size. © 2014 Elsevier B.V.
Removal of H2S using a natural clay modified with a surfactant and incorporating Cu, Fe and Zn into the structure [Remoción de H2S utilizando una arcilla natural modificada con un surfactante e incorporando Cu, Fe y Zn en la estructura]
Semprun L.,University of Zulia |
Solano R.,University of Zulia |
Sanchez J.,University of Zulia |
Carruyo G.,University of Zulia |
And 6 more authors.
Revista Tecnica de la Facultad de Ingenieria Universidad del Zulia | Year: 2011
Mesoporous solids were used for hydrogen sulfide removal from stream H 2S-Air. These solids were synthesized from a natural montmorillonite clay (STx-1) using the template method with a non-ionic surfactant and exchanged with Fe3+, Cu2+ and Fe3+-Cu2+; additionally, MgO/surfactant-clay solids impregnated with different contents of Zn, Fe-Zn and Cu-Zn were also prepared. The solids were characterized by using XRF, XRD, surface area, TPR and TGA-DTG. An increase in the surface area, pore volume and mesoporosity of STx-1 modified with surfactant was observed. The natural clay modified with surfactant and exchanged with copper cation enhanced the H2S breakthrough capacity. The STx-1 clay impregnated with zinc improved H2S removal, which increased with increasing the zinc content.
Fernandez-Delgado M.,Venezuelan Institute for Scientific Research |
Rojas H.,Central University of Venezuela |
Duque Z.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Suarez P.,Simon Bolivar University of Venezuela |
And 3 more authors.
Revista do Instituto de Medicina Tropical de Sao Paulo | Year: 2016
Vibrio cholerae represents a significant threat to human health in developing countries. This pathogen forms biofilms which favors its attachment to surfaces and its survival and transmission by water or food. This work evaluated the in vitro biofilm formation of V. cholerae isolated from clinical and environmental sources on stainless steel of the type used in food processing by using the environmental scanning electron microscopy (ESEM). Results showed no cell adhesion at 4 h and scarce surface colonization at 24 h. Biofilms from the environmental strain were observed at 48 h with high cellular aggregations embedded in Vibrio exopolysaccharide (VPS), while less confluence and VPS production with microcolonies of elongated cells were observed in biofilms produced by the clinical strain. At 96 h the biofilms of the environmental strain were released from the surface leaving coccoid cells and residual structures, whereas biofilms of the clinical strain formed highly organized structures such as channels, mushroom-like and pillars. This is the first study that has shown the in vitro ability of V. cholerae to colonize and form biofilms on stainless steel used in food processing. © 2016, Instituto de Medicina Tropical de Sao Paulo. All rights reserved.
Montes D.,University of Zulia |
Tocuyo E.,University of Zulia |
Gonzalez E.,University of Zulia |
Rodriguez D.,University of Zulia |
And 4 more authors.
Microporous and Mesoporous Materials | Year: 2013
Natural gas, a valuable energy carrier, can be used as a fuel or as a raw material for the production of synthesis gas and hydrogen. However, significant quantities of undesirable contaminants, especially hydrogen sulfide (H 2S), generate harmful environmental emissions. The objective of this work was to develop a scavenger system for the H2S removal at room temperature. The potential of mesoporous silica molecular sieve (MSU-1) supported ZnO or CuO adsorbents has been studied at room temperature for H 2S removal to develop a more effective adsorbent for this important application. Zn2+ or Cu2+ loadings of 10, 20 and 30 wt.% were incorporated by the incipient wetness method. The obtained solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature programmed reduction (TPR), scanning electron microscopy (SEM) and N2 adsorption/desorption, using the BET method, to investigate their various characteristics. The MSU-1 support did not show activity for H2S removal, however the addition of copper or zinc increased the removal performance. The most active solids for H2S were 10Zn/MSU-1 (42.3 mg g-1) and 20Cu/MSU-1 (19.2 mg g-1). A decrease in H 2S removal was observed at a zinc loading higher than 10 wt.% (14.8 and 11.5 mg g-1 for 20 and 30Zn/MSU-1), while 10Cu/MSU-1 presented a low adsorption capacity (10.9 mg g-1) and 30Cu/MSU-1 has a similar performance than that of 20Cu/MSU-1. The adsorption capacity of the obtained materials strongly depends on the pore system as well as the well-proportioned distribution of the active phase inside the porous material and the size of metal oxide nanoparticles. © 2012 Elsevier Inc. All rights reserved.
Purification of mwcnt and its characterization by scanning electron microscopy and thermogravimetric analysis [Purificación de nanotubos multicapa y su caracterización por microscopia electrónica de barrido y análisis termogravimétrico]
Hernandez V.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Arevalo J.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Plaza E.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Diaz L.,Venezuelan Institute for Scientific Research |
And 4 more authors.
Acta Microscopica | Year: 2013
Carbon nanotubes (CNTs) have been in recent years under studies due to its importance in the application for the preparation of new materials. One of the challenges after chemical vapor deposition (CVD) syntheses is the metallic and support removal. In this work we pressent the CNTs purification in acidic medium at various concentrations of hydrochloric acid, in order to evaluate the effects of acid on the morphology of the nanotubes and the reduction of residual metallic and support species. This study was performed using scanning electron microscopy (SEM), energy dispersive of X-ray (EDX) and thermogravimetric (TGA) techniques.
Plaza E.,Venezuelan Institute for Scientific Research |
Briceno-Fuenmayor H.,Venezuelan Institute for Scientific Research |
Arevalo J.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Atencio R.,Venezuelan Institute for Scientific Research |
Corredor L.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit
Journal of Nanoparticle Research | Year: 2015
The growth of carbon nanotubes (CNTs) under a controlled electric field in a chemical vapor deposition system is investigated. We evaluate the influence of this external field on the morphological and structural characteristics of CNTs. Scanning electron microscopy results display a large presence of carbonaceous material in the positive plate, which appear to be a consequence of the attraction of electric forces over the electronically unbalanced cracked carbon molecules in the heating zone. We also observe a growth behavior for CNTs, in which catalyst particles are localized either at the bottom or the upper part of the nanotube, depending on the intensity and direction of the electric field. A Raman analysis from all obtained carbon materials shows the presence of two peaks, corresponding to the D ~ 1340 cm−1 and G ~ 1590 cm−1 bands attributed to multiwall CNTs. The average diameter of the CNTs is in the range between 90 and 40 nm. These results provide experimental evidence for the dependence of the catalyst and subtract interaction on the growing mechanism, in which weak chemical or electronic interactions could stimulate a top-growing as the strongest base-growing process. © 2015, Springer Science+Business Media Dordrecht.
Naranjo-Briceno L.,Institute Estudios Avanzados IDEA |
Pernia B.,Institute Estudios Avanzados IDEA |
Guerra M.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Demey J.R.,Institute Estudios Avanzados IDEA |
And 6 more authors.
Microbial Biotechnology | Year: 2013
Large amount of drilling waste associated with the expansion of the Orinoco Oil Belt (OOB), the biggest proven reserve of extra-heavy crude oil (EHCO) worldwide, is usually impregnated with EHCO and highly salinized water-based drilling fluids. Oxidative exoenzymes (OE) of the lignin-degrading enzyme system (LDS) of fungi catalyse the oxidation of a wide range of toxic pollutants. However, very little evidences on fungal degradation or biotransformation of EHCO have been reported, which contain high amounts of asphaltenes and its biodegradation rate is very limited. The aims of this work were to study the ability of Pestalotiopsis palmarumBM-04 to synthesize OE, its potential to biotransform EHCO and to survive in extreme environmental conditions. Enzymatic studies of the LDS showed the ability of this fungus to overproduce high amounts of laccase (LACp) in presence of wheat bran or lignin peroxidase (LIPp) with EHCO as sole carbon and energy source (1300 U mgP-1 in both cases). FT-IR spectroscopy with Attenuated Total Reflectance (ATR) analysis showed the enzymatic oxidation of carbon and sulfur atoms in both maltenes and asphaltenes fractions of biotreated EHCO catalysed by cell-free laccase-enriched OE using wheat bran as inducer. UV-visible spectrophotometry analysis revealed the oxidation of the petroporphyrins in the asphaltenes fraction of biotreated EHCO. Tolerance assays showed the ability of this fungus to grow up to 50000 p.p.m. of EHCO and 2000mM of NaCl. These results suggest that P.palmarumBM-04 is a hopeful alternative to be used in remediation processes in extreme environmental conditions of salinity and EHCO contamination, such as the drilling waste from the OOB. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.
Characterization by scanning electron microscopy of micro and nano spheres obtained by naphtalene using chemical vapor deposition [Caracterización por microscopía electrónica de barrido de micro y nanoesferas de carbono obtenidas a partir de naftaleno empleando la técnica de deposición química en fase de vapor]
Diaz-Chacon L.C.,Venezuelan Institute for Scientific Research |
Arevalo-Fester J.E.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Plaza-Pirela E.V.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
Atencio-Fuenmayor R.,Venezuelan Institute for Scientific Research |
Atencio-Fuenmayor R.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit
Acta Microscopica | Year: 2011
Carbon micro-/ nanospheres synthesized by CVD using naphthalene as a precursor were characterized by image analysis obtained by scanning electron microscopy (size and shape descriptors). The analysis allowed to observe the influence of reaction temperature on particle size. This behavior is probably due to the higher temperature, higher is the deposition rate, which leads to a structural rearrangement and therefore a more crystalline material. This analysis technique showed to be a versatile and effective pathway in order to study carbon micro-/nano structures morphology.
Toro R.,University of Los Andes, Venezuela |
Bruno-Colmenarez J.,Instituto Zuliano Of Investigaciones Tecnologicas Inzit |
De Delgado G.D.,University of Los Andes, Venezuela |
Delgado J.M.,University of Los Andes, Venezuela
Powder Diffraction | Year: 2013
Clenbuterol hydrochloride is an active pharmaceutical ingredient usually prescribed for treatment of respiratory diseases due to its activity as a decongestant and bronchodilator. It has also been used as a performance- enhancing drug. In the PDF-4/Organics 2012 database there are six entries related to this compound: three for its hydrochloride phase calculated using single-crystal data, two for a MeOH and a DMSO solvate of two Cu-clenbuterol complexes, and one experimental unindexed pattern. In this contribution the powder diffraction pattern and the crystal structure, determined using single crystal X-ray diffraction techniques of clenbuterol hemihydrate, C12H18Cl2N2O·0.5H2O, an unreported phase, are presented. Copyright © International Centre for Diffraction Data 2013.