Artículos y presentaciones en Congresos

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  • Documento de conferencia
    Acceso Abierto
    Aplicación tecnológica de arcillas (acopios) de la sucesión superior de la formación Cerro Largo, Buenos Aires, Argentina
    (1996) Garrido, Liliana B.; Zalba, Patricia Eugenia; Pereira, Enrique
    Based on mineralogical, physicochemical and technological characterization, the brownish and red clays of the upper pelitic succession of the Cerro Largo Formation, Sierras Bayas, Province of Buenos Aires, recently redefined as Olavarría Formation, composed of predominant illitic material, with impurities of quartz, calcite, siderite, hematite, goethite and pyrite, are suitable for red ceramic producís of low water absorption (15%). Preliminary controlled mixtures of the two varieties found (brownish and red), with different technological properties, constitute a better quality product than the ones obtained with the individual clays, wen with the addition of 3-5% bentonite.
  • Artículo
    Acceso Abierto
    La confección de pigmentos en la producción de cerámica arqueológica (La Aguada, Catamarca, Argentina)
    (Sociedad Argentina de Antropología, 2002) Zalba, Patricia Eugenia; Zagorodny, Nora; Balesta, Bárbara; Morosi, Martín Eduardo
    En este trabajo se analizan muestras minerales clasificadas como "pigmentos" (Wolters F. m.s.) halladas en contextos funerarios en el cementerio de La Aguada (Depto. de Belén, Prov. de Catamarca). Este materialforma parte de la Colección Benjamín Muniz Barreto del Museo de La Plata. Las tumbas excavadas totalizan doscientas. En doce unidades de entierro se registraron diecisiete muestras de "pigmentos" presentando algunos de ellos, evidencias de haber sido amasados en forma de panes. Se realizó un análisis contextual de las tumbas en donde fueron localizados los pigmentos. Los mismos fueron sometidos a análisis mineralógicos y químicos a fin de determinar su composición y posible procedencia. Este estudio apunta a dilucidar una etapa dentro de la secuencia operativa de la manufactura cerámica, como también a recuperar la significación de la presencia de los materiales analizados en este tipo de contexto.
  • Documento de conferencia
    Acceso Abierto
    Conservacion de objetos expuestos a la luz y la influencia del medio ambiente en la conservacion del patrimonio
    (Laboratorio de Entrenamiento Multidisciplinario para la Investigación Tecnológica (LEMIT), 2002) Prieto, Nelly H.
    Este trabajo se basa en una observación museológica hacia la forma en que ciertos objetos están expuestos a la luz natural o artificial, sobre todo en los Museos de carácter histórico- ambientales. En nuestra circunstancia socio-cultural actual, es imprescindible una reflexión profunda respecto a la conservación del patrimonio. Muchas veces les damos distintas escalas de valores al patrimonio y nos olvidamos de las pequeñas cosas, que también hacen a la trascendencia de un hombre y/o de una circunstancia cultural de una región en una determinada época. (C. Moreno, 2000). (Párrafo extraído del texto a modo de resumen)
  • Artículo
    Acceso Abierto
    Illite K–Ar dating and crystal growth processes in diagenetic environments: a critical review
    (2004) Meunier, Alain; Velde, Bruce; Zalba, Patricia Eugenia
    K–Ar dating of illitic minerals is commonly used in studies of diagenetic series applied to oil prospecting. In spite of a great number of specialized papers, some problems remain unresolved. These are mostly due to a misunderstanding of the argon accumulation process during illitization. Criteria for identifying detrital–authigenic mineral mixtures, crystal ripening, fast precipitation or continuous nucleation-growth processes are discussed using K–Ar data available in the literature. Using different parameters, such as Dage (age K–Ar ) age strati), D cryst (diagenetic ageK–Ar ) age strati) or D frac (age K–Arfraction ) age K–Ar finest), it is shown that the K–Ar age significance depends on the illite nucleation–growth processes. A ‘diagenetic age’ is obtained when these processes are rapid (the K2O accumulation period is shorter than 2r). If lower than this value, the K–Ar ratio depends on the proportions of new and old particles, respectively, which are controlled by the relative rates of nucleation, crystal growth and ripening.
  • Artículo
    Acceso Abierto
    Middle Permian Telodiagenetic Processes in Neoproterozoic Sequences, Tandilia System, Argentina
    (2007) Zalba, Patricia Eugenia; Manassero, Marcelo; Laverret, Emmanuel; Beaufort, Daniel; Meunier, Alain; Morosi, Martín Eduardo; Segovia, Laura
    In the Tandilia Basin, Buenos Aires Province, Argentina, we study the genesis of mud beds and pipes in the Loma Negra Formation (limestones), Sierras Bayas area, together with the emplacement of alunite and aluminum phosphate sulfate (APS) minerals in the Las Aguilas Formation, Barker area. All these features are related to basin inversion, uplift, erosion, and injection or expulsion, or infiltration of fluids and oxidation reactions in the exhumed rocks during a telodiagenetic stage. On the basis of K--Ar dating of alunite in the Las Aguilas Formation (claystones) giving an age of 254 ± 7 Ma (middle Permian), these processes are considered to be linked to a major geological event which affected these Neoproterozoic lithostratigraphic units: the folding of the Ventania System, located 150 km to the SW of the study area.
  • Artículo
    Acceso Abierto
    Preservation of Biogenerated Mixed Facies: A Case Study from the Neoproterozoic Villa Mónica Formation, Sierra La Juanita, Tandilia, Argentina
    (2010) Zalba, Patricia Eugenia; Manassero, Marcelo; Morosi, Martín Eduardo; Conconi, María Susana
    The aim of this contribution was to show through field work and mineralogical microtextural studies a complex history of weathering and diagenesis in the Villa Mónica Formation, the most ancient Neoproterozoic unit of the Tandilia System and to present a proposal of a paragenetic sequence. This unit also shows microbially induced structures described here for the first time. At the Estancia La Siempre Verde, La Placeres and Don Camilo quarries, Sierra La Juanita, near Barker locality, the Villa Mónica Formation is composed of carbonate facies, classically defined for more than 40 years as siliciclastic facies and of reinterpreted mixed facies: carbonate/siliciclastic and heterolithic respectively, both bearing biosignatures. The carbonates are represented by well-preserved columnar head stromatolite boundstones and by laminar microbial mat deposits. Both of them were the host rocks - identified here for the first time - of individual or random aggregates of pyramidal quartz megacrystals and they were later dolomitized, silicified, illitized and hematized. The siliciclastics are composed of quartz grains trapped within both the stromatolites and the microbial mats, of illitic siltstones and claystones and of quartzitic sandstones. Illuviation processes transported cutans to lower horizons. Syndiagenesis involved dolomitization and silicification while burial diagenesis produced pressure-solution effects by overburden and neoformation of minerals: diagenetic illite with rutile needles, among others. Compressive movements from the SW, responsible for basin inversion: telodiagenesis (uplift, fracturing, folding and introduction of meteoric fluids), affected the Villa Mónica Formation with neoformation/transformation of minerals: kaolinite, halloysite and smectite, development of slickensides (stress cutans) and ferriargillans, hydration, dedolomitization and calcification.
  • Artículo
    Acceso Abierto
    Microscale Diagnostic Diagenetic Features in Neoproterozoic and Ordovician Units, Tandilia Basin, Argentina: A Review
    (2010) Zalba, Patricia Eugenia; Morosi, Martín Eduardo; Manassero, Marcelo; Conconi, María Susana
    This review is the result of many years of research on stratigraphical correlation, sedimentology and mineralogy of one of the oldest sedimentary basins of Argentina that experimented numerous diagenetic changes along the evolution of its geological history: Tandilia. Previous and new data are presented and supported with photographs that illustrate different aspects of microscale diagnostic features of diagenesis recorded in weathered crystalline basement rocks and the overlying sedimentary succession represented by the Neoproterozoic Villa Mónica, Olavarría, Cerro Largo and Las Aguilas formations and the Late Ordovician Balcarce Formation. The study gathers optical and scanningelectron microscopydata supported byX-ray diffractionanalysis. The finding of Microbially Induced Sedimentary Structures (MISS) in siliciclastic and mixed facies helped to unveil hidden biosignatures, fundamental to understanding the origin of life on Earth.
  • Artículo
    Embargado
    Dawsonite in tuffs and litharenites of the Cerro Castaño member, Cerro Barcino Formation, Chubut Group (Cenomanian), Los Altares, Patagonia, Argentina
    (2011) Zalba, Patricia Eugenia; Conconi, María Susana; Morosi, Martín Eduardo; Manassero, Marcelo; Comerio, M.
    tractDawsonite, NaAlCO3(OH)2, occurs as a replacement, cement, and fracture filling in continental, zeolitized and silicified vitric tuffs and litharenites of the Cenomanian Cerro Castaño Member, Cerro Barcino Formation, Chubut Group, Patagonia, Argentina. Analcime is the only associated zeolite; it replaces the vitric masses and also fills fractures and cavities. Dawsonite and analcime display an inverse ratio. Textural relationships indicate that dawsonite is a pseudomorph after oligoclase, quartz, vitric shards, and vitric masses; it coexists with diagenetic quartz cement and postdates analcime, calcite, and hematite cements. Unaltered crystals of high sanidine postdate all other cements generated. Silicification of the tuffs is likely to have occurred in various stages during the diagenetic history of the sequence. Hypabyssal bodies of alkaline basic rocks of the El Buitre – El Canquel Formation, which intruded regionally the Cerro Castaño Member during Eocene time, are interpreted to be responsible for the introduction of CO2 gas at high partial pressures, together with sodium, which led to dawsonite formation. Diagenetic quartz, at a late stage of silicification, is related to the transformation of oligoclase and analcime to dawsonite, also releasing Na and Ca into the system. The d13C (PDB) values of dawsonite, in the range –1.2 to –2.4‰, attest to alkaline igneous activity in the Cerro Castaño Member during the Eocene and, in addition, set a limit on the age of the dawsonite.
  • Artículo
    Acceso Abierto
    Neoproterozoic peritidal facies of the Villa Mónica Formation, Sierra La Juanita, Tandilia, Argentina
    (Asociación Geológica Argentina, 2012) Manassero, Marcelo; Zalba, Patricia Eugenia; Morosi, Martín Eduardo
    From field observations and petrographic studies, a complex association of peritidal carbonate and siliciclastic facies have been recognized in the Villa Mónica Formation (Neoproterozoic), Sierra La Juanita, outcropping at the quarries of Estancia La Siempre Verde, Estancia La Placeres and Estancia Don Camilo, where carbonate facies have not been described ´in situ` since their discovery in 1967. Three different detailed stratigraphic sections are fully described. On the one hand, calcareous facies (well-preserved head stromatolites) have developed in a shallow subtidal to lower intertidal environment. Laminated microbial mats, with millimetric to centimetric scale siliciclastic intercalations, were deposited in low-energy intertidal conditions. Short-lived continental input of quartzose clastic sediments did not obliterate the microbial colonies, which grow following a pattern of thin cycles. On the other hand, heterolithic facies, developed in high-energy intertidal conditions towards the top of the succession illustrate progressive change in the paleoenvironmental conditions which evolved from a shallow prograding carbonate platform, with periodical sea level oscillations, to siliciclastic tidal influenced littoral conditions with minor development of microbial mat deposits. The recognition of ‛MISS’(microbially induced sedimentary structures) represented by microbial mats developed in siliciclastic facies was decisive for the evaluation of paleoenvironmental conditions and for the decision to assign heterolithic lithofacies described in this paper to the Villa Mónica Formation. These microscopical structures suggest and alternation of organic microbial activity with tractive and suspensive events. The coast line was probably oriented N-S with the deeper facies located to the west. A paleoenvironmental model is proposed for the area.
  • Documento de conferencia
    Acceso Abierto
    Reutilización del cromo(III) contenido en el líquido residual de curtido
    (2013) Tavani, Eduardo Luis; Lacour, Norman A.; Hintermeyer, Blanca H.
    En este trabajo se estudió la reutilización del cromo(III) disuelto en el líquido residual de curtido. El tratamiento se inició con la separación de grasas y proteínas desnaturalizadas por tamizado en combinación con ultrafiltración. La composición química lograda con esta metodología fue: 0,99 gL-1 de cromo(III); 12,51 gL-1 de sodio, 11,20 g L-1 de cloruro, 11,53 g L-1 de sulfato, 0,18 g L-1 de grasas, 0,26 g L-1 de proteínas desnaturalizadas y pH 3,63. A continuación se procedió a descontaminar el efluente parcialmente desprovisto de las referidas sustancias orgánicas aplicando tres procesos diferentes. Bajo las condiciones más propicias se obtuvieron: un sobrenadante con 1,8 mg L-1 de Cr3+ por medio de precipitación alcalina, un permeado con 1,6 mg L-1 de Cr3+ mediante ósmosis inversa y una solución de equilibrio con 4,5 mg L-1 de Cr3+ por adsorción. Las fases portadoras del catión removido con dichas tecnologías fueron analizadas a fin de determinar sus principales características fisicoquímicas. El contenido de Cr3+ para cada una de ellas fue: 24,99% p/p en el precipitado, 2,09 g L-1 en el concentrado y 32,8 mg por g de adsorbente. Finalmente, se evaluó la preparación de un licor apto para el curtido de piel vacuna que incluyera en su composición el cromo(III) recuperado por tecnología de membrana.
  • Documento de conferencia
    Acceso Abierto
    Purificación de sistemas equivalentes a efluentes coloreados de curtiembres utilizando minerales arcillosos
    (2013) Stábile, Franco M.; Volzone, Cristina; Gallegos, Norma G.; Stábile, Franco Matías
    En la actualidad existen numerosos problemas ambientales provocados por las actividades industriales, que conducen a efectos nocivos para el ser humano y su entorno. Es necesario poner énfasis en encontrar procedimientos adecuados para disminuir los efectos contaminantes de las diversas actividades industriales. Efluentes conteniendo colorantes pueden proceder de diferentes industrias, entre las cuales puede mencionarse la industria del curtido. Las concentraciones de los tintes en los mencionados efluentes deben ajustarse a las normativas vigentes antes de su disposición final. Uno de los colorantes mas utilizados para el teñido de los cueros es el llamado negro acido (acid black). Si bien, el colorante mencionado está presente en la mayoría de los efluentes de la industria del cuero, ha sido muy poco estudiada su eliminación. Actualmente, diferentes tipos de materiales son evaluados para ser utilizados como adsorbentes, con el objeto de reducir o eliminar la concentración contaminante. Los minerales arcillosos, se caracterizan por ser de bajo costo y amplia disponibilidad, y suelen ser utilizados como adsorbentes, por sus pequeños tamaños de partícula y capacidades de intercambio (Bailly y col., 2010; Volzone y col., 2012). Estos minerales suelen encontrarse en la naturaleza acompañados por impurezas, las cuales pueden ser removidas. El objetivo del presente trabajo consiste en analizar la posibilidad de utilizar sólidos arcillosos modificados, para ser considerados como potenciales adsorbentes de colorantes presentes en efluentes de la industria del curtido. En particular se analizará la capacidad de retención del colorante comercial Negro Acido 210, utilizando un mineral arcilloso nacional de la zona de San Juan y otro importado, ambos modificados con una sal cuaternaria.
  • Artículo
    Acceso Abierto
    Firing transformations of an argentinean calcareous commercial clay
    (Associacao Brasileira de Cerâmica, 2013) Serra, Maria Florencia; Conconi, María Susana; Suárez, Gustavo; Aglietti, Esteban Fausto; Rendtorff Birrer, Nicolás Maximiliano
    Mineralogical transformations caused by firing are usually studied by XRD methods only semi-quantitatively. In this work the original mineral disappearance and the neo-mineralization were evaluated quantitatively. Furthermore an indirect non crystalline phase quantification was performed under 1100 ºC was also carried out using the quartz content as internal standard. This study specifically discusses the behavior of an Argentinean white calcareous earthenware commercial when subjected to traditional ceramic firing, besides the technological importance of this particular material, it acts as a model for other clay based ceramic materials. Materials were subjected to thermal treatments between 700 ºC and 1100 ºC. A preliminary sintering characterization was carried out by contraction and porosity evolution. Simultaneous thermogravimetric and differential thermal analysis (TG-DTA) was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, a quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed to characterize the crystalline phases present in both the clay and in the materials obtained after different thermal treatments. The actual chemical reactions are proposed. The phases identified after firing at traditional working temperature (1040 ºC) are quartz, plagioclase, and the Spinel type alumino-silicate, accompanied by the non-diffracting un-reacted metakaolin and some amount of amorphous glassy phase. At intermediate temperatures (900 ºC) the presence of gehlenite was also detected. The carbonates (calcite and dolomite) presence and decomposition were also evaluated and demonstrated to determine the sintering characteristics of this material.
  • Documento de conferencia
    Acceso Abierto
    Uso de ligandos orgánicos en la fitoextracción de plomo por ricino (Ricinus communis L.)
    (2014) Miniño, Hugo; Rendina, Alicia; Barros, María J.; Bursztyn Fuentes, Amalia Lara; Ríos, Alejandra de los; Wassner, Diego; Iorio, Alicia F. de
    Especies vegetales con alta producción de biomasa pueden ser utilizadas para la remoción de metales mediante la cosecha de la biomasa aérea. Sin embargo, la baja disponibilidad de los metales en el suelo, frecuentemente limitan su absorción y translocación, reduciendo la eficiencia del proceso de fitoextracción. La adición de ligandos orgánicos al suelo constituye una estrategia para aumentar la disponibilidad de los metales. Un experimento en macetas fue llevado a cabo para evaluar la fitoextracción de Pb por Ricino (Ricinus communis L.) mediante la aplicación de EDTA (5.1 mmol.kg-1 de suelo), EDDS (5.1 mmol.kg-1), ácido cítrico (5.1 mmol.kg-1) y extracto de compost (66 mg C.kg-1) a un suelo contaminado con 600 mg.kg-1 de Pb. Dos formas de aplicación fueron ensayadas: a) una única aplicación de las dosis, 7 días antes de la cosecha y b) tres aplicaciones separadas de 1/3 de la dosis, realizadas a los 21, 14 y 7 días antes de la cosecha. Ninguno de los tratamientos disminuyó la biomasa de las plantas respecto del control. El EDTA y EDDS aumentaron significativamente la concentración de Pb en parte aérea y raíz de las plantas con respecto al control, en cambio el ácido cítrico y el extracto de compost no tuvieron efecto sobre la concentración de Pb en las plantas. El EDTA (5.1 mmol.kg-1) aplicado 7 días antes de la cosecha de las plantas fue el tratamiento más efectivo en solubilizar Pb asociado a óxidos de Fe y Mn, carbonatos y materia orgánica, lo cual favoreció la absorción del Pb por las raíces y su translocación a los tejidos aéreos de las plantas. El valor del factor de bioconcentración (1.03) y del factor de translocación (1.73) de Ricino mediante la incorporación de EDTA en una aplicación, muestran la aptitud potencial de esta especie vegetal para ser utilizada en la remediación de suelos contaminados con Pb, siendo aceptable el tiempo que insume el proceso de fitoextracción.
  • Documento de conferencia
    Acceso Abierto
    Does “black shales” suffice for lithological changes in transgressive facies? The case of the Agua de la Mula Member (Agrio Formation), Neuquen Basin, Argentina
    (2014) Comerio, Marcos; Pazos, Pablo José; Zalba, Patricia Eugenia
    “Black shales” ¿Es suficiente para denotar cambios litológicos en facies transgresivas? Caso del Miembro Agua de la Mula (Formación Agrio), Cuenca Neuquina, Argentina Se estudió, por medio de microscopía óptica y electrónica de barrido, así como por difracción de rayos X y contenido de carbono orgánico, la variabilidad de litofacies correspondiente a la etapa transgresiva basal del Miembro Agua de la Mula de la Formación Agrio, a escala de cuenca. Se pudieron diferenciar tres grupos de sedimentitas de grano fino: (i) un grupo dominados por componentes intracuencales derivados de la producción orgánica y carbonática, (ii) otro con altos porcentajes de componentes terrígenos y (iii) un tercer grupo con predominio de minerales autigénicos. Además de procesos de baja energía, como el de decantación a partir de material en suspensión, se documentaron corrientes tractivas, desarrollo de matas microbianas y bioturbación. Los procesos sedimentarios reconocidos sugieren que durante la depositación los escenarios fueron dinámicos y variables a distintas escalas, tanto en sentido lateral como vertical, y no relativamente estables como antes se presumía.
  • Documento de conferencia
    Acceso Abierto
    Adsorción de Tiabendazol en montmorillonita y ODTMAmontmorillonita: efecto del Cu²⁺
    (2015) Gamba, Martina; Yarza, Florencia; Cunci, I.; Torres Sánchez, Rosa María
    El Tiabendazol (TBZ) es un fungicida post-cosecha de amplia aplicación en Argentina, con capacidad de coordinarse a través de sus átomos de nitrógeno a iones metálicos como el Cu²⁺. En estudios previos se observó un aumento de adsorción de TBZ en montmorillonita (Mt) y organo-montmorillonita (OMt, sintetizadas por intercambio catiónico con octadeciltrimetilamonio, ODTMA) intercambiadas con Cu²⁺ (MtCu y OMtCu, respectivamente) asignada a la formación de complejos estables del Cu²⁺ con el TBZ. Continuando este estudio, en el presente trabajo se evalúan los mecanismos de adsorción del TBZ y los adsorbentes a través de isotermas de adsorción en distintas relaciones adsorbente/solución y análisis de FTIR y pérdidas de masa (TG) de los productos de adsorción. El ajustaron los datos experimentales con el modelo General Langmuir-Freundlich el cual indicó un aumento de qmax en todas las muestras, con la disminución de la relación sólido/solución, evidenciando mayores qmax y Ks las muestras con Cu. En la muestra MtCu, de mayor contenido en TBZ, la adsorción del fungicida produjo corrimientos de las bandas asignadas a los estiramientos C=N del anillo tiazol e imidazol, estiramiento C=C y deformación C-H de la estructura aromática (1578, 1481, 1407 y 1306 cm-1, respectivamente) indicando la existencia de interacciones entre los átomos de N del TBZ y el Cu. La pérdida de masa de 3,4 y 2,2 % para las muestras MtCu-TBZ y Mt-TBZ respectivamente, correspondiente a la descomposición de los compuestos orgánicos, fue coherente con las isotermas. El análisis de los datos de ATD-TG para las muestras OMt y OMtCu, se vio dificultado por el solapamiento de la temperatura de descomposición del surfactante con la del fungicida.
  • Artículo
    Acceso Abierto
    Global diversity, population stratification, and selection of human copy number variation
    (2015) Sudmant, Peter H.; Mallick, Swapan; Nelson, Bradley J.; Hormozdiari, Fereydoun; Krumm, Niklas; Huddleston, John; Coe, Bradley P.; Baker, Carl; Nordenfelt, Susanne; Bamshad, Michael; Jorde, Lynn B.; Posukh, Olga L.; Sahakyan, Hovhannes; Watkins, Scott; Yepiskoposyan, Levon; Abdullah, M. Syafiq; Bravi, Claudio M.; Capelli, Cristian; Hervig, Tor; Wee, Joseph T. S.; Tyler-Smith, Chris; van Driem, George; Gallego Romero, Irene; Jha, Aashish R.; Karachanak-Yankova, Sena; Toncheva, Draga; Comas, David; Henn, Brenna; Kivisild, Toomas; Ruiz-Linares, Andres; Sajantila, Antti; Metspalu, Ene; Parik, Jüri; Villems, Richard; Starikovskaya, Elena B.; Ayodo, George; Beall, Cynthia M.; Di Rienzo, Anna; Hammer, Michael; Khusainova, Rita; Khusnutdinova, Elza; Klitz, William; Winkler, Cheryl; Labuda, Damian; Metspalu, Mait; Tishkoff, Sarah A.; Dryomov, Stanislav; Sukernik, Rem; Patterson, Nick; Reich, David; Eichler, Evan E.
    In order to explore the diversity and selective signatures of duplication and deletion human copy number variants (CNVs), we sequenced 236 individuals from 125 distinct human populations. We observed that duplications exhibit fundamentally different population genetic and selective signatures than deletions and are more likely to be stratified between human populations. Through reconstruction of the ancestral human genome, we identify megabases of DNA lost in different human lineages and pinpoint large duplications that introgressed from the extinct Denisova lineage now found at high frequency exclusively in Oceanic populations. We find that the proportion of CNV base pairs to single nucleotide variant base pairs is greater among non-Africans than it is among African populations, but we conclude that this difference is likely due to unique aspects of non-African population history as opposed to differences in CNV load.
  • Artículo
    Acceso Abierto
    Comparison of Imazalil Removal onto Montmorillonite and Nanomontmorillonite and Adsorption Surface Sites Involved: An Approach for Agricultural Wastewater Treatment
    (2015) Gamba, Martina; Flores, Federico Manuel; Madejová, Jana; Torres Sánchez, Rosa María
    To remove fungicide Imazalil (IMZ) (commercial formulation) from agricultural wastewater, adsorption was performed and compared among montmorillonite (Mt) and four organo-Mts (OMts), with different octadecyltrimethylammonium (ODTMA) loadings. The agglomerates size increase of OMts with respect to Mt found encourages the use of the former in agricultural wastewater treatment. Characterization of the OMts adsorbents by powder X-ray diffraction, infrared spectroscopy, and thermogravimetric analyses, indicated that ODTMA was present in the interlayer with different molecular arrangements, a diminution of the thermal stability of the OMts and an increase of ODTMA loading being observed at the same time. Zeta potential measurements showed electric surface charge reversion from negative to positive when the surfactant loading exceeded 100% of the clay cation exchange capacity (CEC). The IMZ adsorption on the raw Mt showed high pH dependence and affinity toward the fungicide, while OMts showed best IMZ adsorption capacity at high IMZ concentrations inversely related with the ODTMA loading. The characterization of IMZ−adsorbed samples indicated that for IMZ−Mt the interaction between IMZH+ and the siloxane surface was electrostatic. For IMZ−OMt samples the presence of new XRD and FTIR peaks suggested different IMZ interlayer arrangements and direct interaction with the surface, respectively. Analysis of zeta potential measurements indicated synergetic effects between the ODTMA and IMZ molecules at the external surface.
  • Artículo
    Acceso Abierto
    The ichnogenus Dictyodora from Late Silurian deposits of central-western Argentina: Ichnotaxonomy, ethology and ichnostratigrapical perspectives from Gondwana
    (2015) Pazos, Pablo José; Heredia, Arturo; Fernández, Diana E.; Gutiérrez, Carolina; Comerio, Marcos
    The association of trace fossils from the Late Silurian Río Seco de los Castaños Formation in central-western Argentina (San Rafael Block) is mainly composed of Dictyodora, including D. scotica, D. tenuis and a new ichnospecies named D. atuelica. The latter shows a tendency to migrate to a deeper level – analogous to D. liebeana’s – which reflects more sophisticated behavioural patterns. The Dictyodora ichnospecies (one of the most diverse assemblages in Gondwana) coexists with Nereites. SEM observations and EDS analyses suggest that the wall structure of Dictyodora could be the result of an activity other than the traditional suggestion of respiration, e.g., feeding. The succession, including some of the levels containing Dictyodora, presents microbially induced sedimentary structures (MISS) that would indicate a photic zone. This discovery favours previous deltaic interpretations instead of the deep-sea fan deposits traditionally suggested for the Siluro-Devonian greywackes of the Cuyania terrane, and particularly for this unit. The abundant Dictyodora, Nereites, Zoophycos and undermat miners ichnofossils, as well as the scarce arthropod trackways, resemble older records in Europe and North America. The studied section is very well ageconstrained, and the autochthonous Gondwana ichnofauna permits to cast doubt on previous interpretations, suggesting that after the Ordovician, microbial mats retreated to marginal marine environments and then spread later in the Carboniferous. More importantly, the occurrence of Dictyodora and Nereites in beds that bear abundant wrinkle structures or records of biofilms in some places is challenging with regard to deep-sea interpretations. Dictyodora is probably not a good stratigraphic indicator, and the provincialism suggested for this ichnogenus may be an artefact of the lack of more complete records in Gondwana.
  • Contribucion a revista
    Acceso Abierto
    Dense mullite–zirconia–zirconium titanateceramiccomposites by reactionsintering
    (2015) Rendtorff Birrer, Nicolás Maximiliano; Gómez, Sofía; Gauna, Matías; Conconi, María Susana; Suárez, Gustavo; Aglietti, Esteban
    Materials from the Al2O3–SiO2–ZrO2and the Al2O3–SiO2–ZrO2–TiO2systems have several high temperature applications because they present the good refractoriness, chemical inertness, adequate mechanical and thermo-mechanical behaviors with a relatively good cost: performance ratio. In this work stoichiometric (3:2:1) molar incompatible mixtures of alumina (Al2O3), zircon (ZrSiO4) and titania (TiO2) were slip casted and sintered in a 1300–1500°C temperature range in order to obtain mullite (3Al2O3·2SiO2), zirconia (ZrO2) and zirconium titanate (ZrTiO4) dense triple ceramic composite. Both sintering and reaction occurred after the thermal treatments. Reaction progress and densification evolutions were established. Dense Triplex composite materials were achieved after 1500°C treatments. The reaction-sintering was followed by XRD, TG–DTA, and dilatometry. Densification started at 1100°C and the chemical reactions only started above 1300°C. Aluminum titanate (Al2TiO5) was found to be an intermediate of the reaction after 1400°C treatments. Materials treated below 1300°C presented a partial densification of the unreacted starting powders. Resulting ceramic materials were characterized. The crystalline phases were evaluated, as well as the texture properties. The achieved microstructure consisted in interlocked multiphase ceramic with zirconia (monoclinic) grains. The achieved Hv andKICreached 9GPa and 4.3MPam1/2respectively. The dense and interlocked ceramic microstructure and relative high mechanical properties of the developed material encourages several high temperature applications. Finally it can be pointed out that after 1500°C treatments some detrimental grain growth was observed.
  • Artículo
    Acceso Abierto
    Monoclinic - tetragonal zirconia quantification of commercial nanopowder mixtures by XRD and DTA
    (University of Chemistry and Technology (Prague), 2015) Gauna, Matías; Conconi, María Susana; Gómez, Sofía; Suárez, Gustavo; Aglietti, Esteban; Rendtorff Birrer, Nicolás Maximiliano
    The phase quantification in ceramic nanopowders presents technological interest for studying and design purposes. Especially in zirconia ceramics where the mechanical and transport properties are strongly affected by the crystalline composition. In this work we present the comparison XRD based methods and differential thermal analysis methods for phase characterization and specially quantification. A complete series of commercial nanopowders mixtures (D50 ≈ 0.1 μm) of monoclinic zirconia (m) and partially stabilized zirconia (t: 3 % yttrium oxide) was studied. X ray diffraction (XRD) was performed and the relation m:t was quantified by the so called Garvie-Nicholson (G-N), Toraya and Rietveld method. A complete reversible DTA analysis was carried out to the same mixtures. Both m-t and t-m martensitic thermal transformations were observed and pondered for the m-ZrO2 containing samples. The graphical integration was performed and employed for the construction of a calibration curve in the studied composition range. The results were compared, the Toraya method presented equivalent results in comparison with the Rietveld method. The G-N method presented appreciable differences (≈ 10 %). To assume a direct proportion of the m-ZrO2 content with the peak area resulted in important errors but if a simple calibration curve is constructed, the DTA method presents accurate quantification with results comparable to the best XRD based quantification.