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Search Results: 1 - 10 of 68041 matches for " José Gregorio Carriazo "
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Scientia Et Technica , 2005,
Abstract: Se caracterizaron dos arcillas naturales mediante fisiadsorción de nitrógeno a 77K, análisis químico e intercambio catiónico y se emplearon en la eliminación de iones contaminantes (Cu2+, Al3+ y Fe3+) en solución. Las eficiencias en la eliminación de estos contaminantes indican la potencialidad de dichos materiales en procesos de descontaminación de aguas residuales.
A study of low-cost adsorbent materials for removing Cr(VI) from aqueous waste effluent Estudio de materiales adsorbentes de bajo costo para remover Cr(VI) de efluentes acuosos
Vargas-Ni?o Claudia,Carriazo José Gregorio,Castillo Serna Elianna
Ingeniería e Investigación , 2011,
Abstract: The present paper shows very high potential for two types of solid (a commercial alumina and material obtained by composting, i.e. matured compost) on Cr(VI) adsorption/elimination in aqueous solution using a concentration range close to those previously detected in waste-water from Colombian industries. Both had important properties for eliminating Cr(VI), the compost being more important as it represents low-cost material. Optimal conditions for chromium adsorption on alumina and compost were established. Initial Cr(VI) alumina concentration was 10 mgL-1, with 100 mL/g volume of solution per adsorbent mass, pH=2.0, 1 hour equilibrium time and 150 rpm stirring. For compost, initial Cr(VI) concentration was = 3 mg L-1, 50 mL/g volume of solution per adsorbent mass, pH=2.5, 3 hour equilibrium time and 150 rpm stirring. The experiments showed that compost adsorption properties could be enhanced by adding small quantities of alumina. Compost could thus be chosen as a promising material for use in bioremediation chromium-containing waste water in a management programme for using solid waste in for minimising environmental impact. El presente estudio muestra el enorme potencial de dos tipos de sólidos diferentes, una alúmina comercial y un material producto del compostaje, en la adsorción/eliminación de Cr(VI) en medio acuoso, en concentraciones de metal equivalentes a las halladas en aguas residuales provenientes de industrias en Colombia. Ambos materiales mostraron propiedades importantes para la eliminación de Cr(VI), considerándose de mayor relevancia el compost por ser un material de bajo costo. Se establecieron las condiciones óptimas para la adsorción de cromo sobre alúmina y sobre compost. Para la alúmina: concentración inicial de Cr(VI) = 10 mgL-1, volumen de solución por masa de adsorbente = 100 mL/g, pH = 2,0, tiempo de equilibrio = 1 hora, y agitación = 150 rpm. Para el compost: concentración inicial de Cr(VI) = 3 mg L-1, volumen de solución por masa de adsorbente = 50 mL/g, pH = 2.5, tiempo de equilibrio = 3 horas, y agitació
Blended Learning Applied to an Introductory Course on Conceptual Physics
Plinio del Carmen Teherán Serme?o,José Gregorio Carriazo,Julio Cesar León Luque
International Journal of Online Engineering (iJOE) , 2010, DOI: 10.3991/ijoe.v6i3.1303
Abstract: In this paper, we show aspects of the commencement of a novel introductory Physics course with conceptual emphasis. An instructional flexible design in the format of blending learning is presented that combines master classes via teleconference with additional activities in a virtual environment of learning orchestrated by LMS Blackboard. In the forums, workshops and virtual laboratories the impact is evaluated as a grading system based on Continuous Personalized Evaluation
Laboratory projects using inquiry-based learning: an application to a practical inorganic course
Carriazo, José G.;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000600029
Abstract: this paper reports how laboratory projects (lp) coupled to inquiry-based learning (ibl) were implemented in a practical inorganic chemistry course. several coordination compounds have been successfully synthesised by students according to the proposed topics by the lp-ibl junction, and the chemistry of a number of metals has been studied. qualitative data were collected from written reports, oral presentations, lab-notebook reviews and personal discussions with the students through an experimental course with undergraduate second-year students at the universidad nacional de colombia during the last 5 years. positive skills production was observed by combining lp and ibl. conceptual, practical, interpretational, constructional (questions, explanations, hypotheses), communicational, environmental and application abilities were revealed by the students throughout the experimental course.
Thermal and structural study of guava (Psidium guajava L) powders obtained by two dehydration methods
Osorio, Coralia;Carriazo, José G.;Barbosa, Helber;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000400016
Abstract: two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. the powders were characterised by sensory and thermal analyses (tga-dsc), infrared spectroscopy (ir), x-ray diffraction (xrd) and scanning electron microscopy (sem). thermal, morphological and structural characterisations showed a similar behaviour for the two solids. tga-dsc and ir showed the presence of pectin as the main constituent of solids. a semi-crystalline profile was evidenced by xrd, and lamellar/spherical morphologies were observed by sem. sensory analyses revealed an aroma highly related to guava. these value-added food products are an alternative to process guava and avoid loss during postharvest handling.
Carriazo,José; Molina,Rafael; Moreno,Sonia;
Revista Colombiana de Química , 2007,
Abstract: in the present work a colombian bentonite (from valle del cauca) was characterized by x-ray diffraction, spectroscopic techniques (ir, nmr and epr) and textural analysis. the results indicate that dioctahedral (aluminian) smectite is the principal component in the natural material. in addition, both 29si nmr and 27al nmr analysis reveal the isomorphous substitution of al3+ by si4+ in the tetrahedral sheet. the epr study shows iron (iii) in octahedral sheet positions of the clay mineral besides ?nanoclusters? probably in oxides or oxyhydroxides form. the textural analysis indicates that the bentonite is predominantly a mesoporous material.
Carriazo,José; Barrera,Mario; Almanza,Ovidio;
Revista Colombiana de Química , 2007,
Abstract: the present paper shows the evaluation of texture, surface and structure changes on a zeolite y employed in the synthesis of solids based on supported platinum. the structure features were analyzed by x-ray diffraction (xrd) whereas the texture and morphologic properties were studied from nitrogen adsorption isotherms (77k) and scanning electron microscopy (sem). in addition, fractal dimension and adsorption potential distribution were determinedall solids. the results show that the synthesis process induces the microporosity formation, maintaining the zeolite structure and without important topographic or energetic alterations on the surface.
Carriazo,José; Molina,Rafael; Moreno,Sonia;
Revista Colombiana de Química , 2008,
Abstract: this work shows the characterization by ir spectroscopy, thermogravimetric analysis (tga), differential thermal analysis (dta) and nuclear magnetic resonance spectroscopy (29sinmrand 27al nmr) of a set of pillared clays synthesized with al, al-fe, al-ce or al-ce-fe polyhydroxocationic solutions. tgadta analyses indicate a favorable thermal effect (higher thermal stability) when ce, fe or ce-fe are added. ir and 29si nmr results reveal a probable formation of a bond between the alumina pillar and the clay (sio4)-tetrahedral sheet, whereas the 27al nmr does not evidence any isomorphous substitution of iron or cerium in the alumina pillars. moreover, by ir spectroscopy was not observed any structural difference between solids pillared with al and those pillared with al-ce, showing that cerium is possibly incorporated in an independent way to the alumina pillar.
Actitudes hacia la química de estudiantes de diferentes carreras universitarias en Colombia
Molina, Manuel F;Carriazo, José G;Farías, Diana M;
Química Nova , 2011, DOI: 10.1590/S0100-40422011000900032
Abstract: this work reports a study on the attitudes of colombian students towards chemistry in different undergraduate programs. the research was performed on 769 students belonging to several chemistry courses, by applying an adaptation of salta and tzougraki's test and using likert's scale. the results revealed that chemistry is being considered as difficult and little useful, but very interesting. thus, the difficulty to learn chemistry may be associated with its language and abstract conceptual nature. in addition, more attention should be given to the class contents and methodologies provided to the students, in order to engage them with those interest aspects and meaningful topics of each program
Impregnación de platino y dimensión fractal en dos tipos de sólidos microporosos
Carriazo,José G.; Barrera-Vargas,Mario; Molina,Manuel F.;
Revista Ingenierías Universidad de Medellín , 2010,
Abstract: this research shows the modification of a zeolite y and a pillared clay (saponite) by impregnation with different platinum quantities (synthesis of pt catalysts). the solids were characterized about the chemical composition and texture. the textural characterization reveals important changes in the solids, showing that in the zeolitic catalysts microporosity is formed, whereas in the pillared clay the microporous structures are partially blocked. fractal dimension (by avnir-jaroniec method) indicates that the topographic features of the pillared clay surface are significantly affected due to the modification with platinum, probably as a consequence of platinum clusters formation.
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