Ordered mesoporous organosilica adsorbents for inorganic pollutants removal from water

Este manuscrito hace un repaso de las contribuciones más importantes sobre el uso de las sílices mesoporosas ordenadas (SMO) modificadas aplicadas a la remoción de contaminantes inorgánicos de matrices acuosas. En primer lugar, se discute brevemente sobre los diferentes caminos para sintetizar este tipo de materiales mesoporosos nanoestrucurados, mencionando también las características estructurales y químicas principales que se obtienen al utilizar cada uno de ellos. Se hace énfasis en los reportes sobre la aplicación de las SMO como adsorbentes para la remediación ambiental, aunque también se mencionan brevemente otros campos donde se utilizan este tipo de sistemas sólidos nanoestructurados. Finalmente se discute en profundidad sobre la síntesis y aplicación de la SMO denominada MCM-41, su modificación con diferentes grupos orgánicos y su desempeño en la remoción de cromo hexavalente de soluciones acuosas de variada composición química. De esta SMO en particular se discute cómo afectan sobre su desempeño como adsorbente el tamaño de partícula y la cantidad y distribución de grupos orgánicos anclados dentro de la red de mesoporos. Finalmente se mencionan algunas estrategias actualmente en estudio que buscan aumentar la estabilidad de la MCM-41 de manera de conseguir un adsorbente efectivo y de larga vida útil.This article reviews the most important contributions on the use of organically modified ordered mesoporous silicas (OMS) for removal of inorganic pollutants from aqueous matrices. First, we briefly discuss the different preparation methods to synthesize this type of nanostructured mesoporous hybrid materials, mentioning the main structural and chemical features than can be obtained. Emphasis is placed on the application of OMS as adsorbents for environmental remediation purposes, although other fields where this type of nanostructured solid systems are used are also briefly mentioned. Finally, a depth discussion on the synthesis and application of the OMS called MCM-41, its modification with different organic groups, and its performance in the removal of hexavalent chromium from aqueous solutions of varied chemical composition is presented. The MCM-41 mesophase is taken as an example to discuss how the particle size and the amount and distribution of organic groups anchored within the mesoporous network affect the performance of these kind of materials as adsorbents. Finally, some possible strategies that seek to improve the stability of the MCM-41 based sorbents for its use in a wide range of operational conditions are mentioned.Fil: Martin, Pedro Pablo. Universidad Nacional de Río Negro; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigaciones y Transferencia de Rio Negro. Sede Choele Choel del Centro de Investigaciones y Transferencia de Rio Negro | Universidad Nacional de Rio Negro. Centro de Investigaciones y Transferencia de Rio Negro. Sede Choele Choel del Centro de Investigaciones y Transferencia de Rio Negro.; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Fellenz, Nicolás Antonio. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigaciones y Transferencia de Rio Negro. Sede Choele Choel del Centro de Investigaciones y Transferencia de Rio Negro | Universidad Nacional de Rio Negro. Centro de Investigaciones y Transferencia de Rio Negro. Sede Choele Choel del Centro de Investigaciones y Transferencia de Rio Negro.; Argentin

Environmental Reactions of Air-Quality Protection on Eco-Friendly Iron-Based Catalysts

A series of iron functionalized hydroxyapatite (Fe/HAP) samples with different metal loading (2 < wt.% Fe < 13) was prepared by a flash ionic exchange procedure from iron(III) nitrate as precursor and tested in some environmental air-quality protection reactions such as the catalytic reduction of NOx by NH3 (NH3-SCR), catalytic oxidation of NH3 (NH3-SCO) and catalytic N2O decomposition. The catalytic performances of the Fe/HAP catalysts were determined under flow conditions as a function of temperature and using reactant concentrations typical of polluting gaseous emissions from industrial vents. Physico-chemical characterization with various techniques of study (UV-DR and Mössbauer spectroscopies, NH3 titration, N2-physisorption, and XRPD analyses) provided valuable information on Fe-speciation, acidity, morphology, and structure of the samples. In general, highly dispersed Fe3+ centers were the predominant species, irrespective of Fe-loading, while just low percentage (≤15%) of FexOy nanoclusters (2 < size/nm < 4) was detected on the samples. As expected, the differences in iron concentration produced a diversified effect of both catalyst properties and catalytic activity, comprising the conversion and selectivity profiles, different for each reaction considered. The obtained results indicate a good potentiality for the eco-friendly Fe-catalysts for some environmental reactions of air protection.Fil: Greta Galloni, Melissa. Università degli Studi di Milano; ItaliaFil: Campisi, Sebastiano. Università degli Studi di Milano; ItaliaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Gervasini, Antonella. Università degli Studi di Milano; Itali

SBA‐15 modified by incorporation of alkali metals: Effect of Its structural changes on the catalytic properties of Fe/SBA‐15 system in the Fischer–tropsch synthesis

A mesoporous SBA‐15 solid is doped with Li, K, or Cs. These systems are used as support of iron nanoparticles, and each composite is utilized as a catalyst in the Fischer-Tropsch synthesis. After the activation treatment, the same Fe species are detected in all solids: Fe3O4, α‐Fe, and Fe2+ inside SBA‐15 walls. However, the species percentages and their distribution are different according to the dopant present. In all "working" catalysts, a mixture of carbides ε´‐Fe2.2C and χ‐Fe2C5, Fe3O4, and ions Fe+2 inside the SBA‐15 walls are found. Alkali cations produce different amounts and strengths of basic sites. At 1 atm and T  = 703 K, the catalytic activity order is: Li > K > no doped > Cs, and the alkali metals favor the production of olefins. At 20 atm, the activity is considerably higher, even at a temperature as low as 543 K, which is attributed to structural properties of the support and to diffusional effects. All catalysts show a promising hydrocarbon production in the gasoline range. The influence of alkali metals is discussed in terms of electrostatic effects, and the limited hydrocarbon chain growth is attributed to the control over size of active iron species.Fil: Cano, Leonardo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Cagnoli, María V.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Bengoa, José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Modifier Adaptation as a Feedback Control Scheme

As a real-time optimization technique, modifier adaptation (MA) has gained much significance in recent years. This is mainly due to the fact that MA can deal explicitly with structural plant-model mismatch and unknown disturbances. MA is an iterative technique that is ideally suited to real-life applications. Its two main features are the way measurements are used to correct the model and the role played by the model in actually computing the next inputs. This paper analyzes these two features and shows that, although MA computes the next inputs via numerical optimization, it can be viewed as a feedback control scheme, that is, optimization implements tracking of the plant Karush-Kuhn-Tucker (KKT) conditions. As a result, the role of the model is downplayed to the point that model accuracy is not an important issue. The key issues are gradient estimation and model adequacy, the latter requiring that the model possesses the correct curvature of the cost function at the plant optimum. The main role of optimization is to identify the proper set of controlled variables (the active constraints and reduced gradients) as these might change with the operating point and disturbances. Thanks to this reduced requirement on model accuracy, MA is ideally suited to drive real-life processes to optimality. This is illustrated through two experimental systems with very different optimization features, namely, a commercial fuel-cell system and an experimental kite setup for harnessing wind energy.Fil: Marchetti, Alejandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas. Universidad Nacional de Rosario. Centro Internacional Franco Argentino de Ciencias de la Información y de Sistemas; ArgentinaFil: de Avila Ferreira, T.. Ecole Polytechnique Federale de Lausanne; FranciaFil: Costello, Sergio Gustavo. Ecole Polytechnique Federale de Lausanne; FranciaFil: Bonvin, Dominique. Ecole Polytechnique Federale de Lausanne; Franci

Effect of iron content on the catalytic properties of activated carbon-supported magnetite derived from biomass

In recent times, the intense human activity has led to an increase of the agriculture wastes in the environment. “In order to find new applications for these materials, the effect of iron content (2.5, 5, 10 and 15%) on the catalytic properties of activated carbon-supported iron oxide, prepared from coconut shells, was studied. The iron amount affected the textural and reducing properties of the solids and particle sizes. Hematite was found for the most iron-poor sample, while particles of magnetite with a core of hematite were found for the others. These catalysts were effective in the methylene blue removal from aqueous solutions by adsorption and Fenton reaction. The solid with 15% of iron was the most active one probably due to the highest iron amount on the surface. These catalysts are environmentally friendly, contributing to the decrease of the solid wastes in the environment as well as to purify textile effluents, preserving water resources.Nos últimos tempos, a intensa atividade humana levou a um aumento de resíduos agrícolas no meio ambiente. Visando a encontrar novas aplicações para estes materiais estudou-se, neste trabalho, o efeito do teor de ferro (2.5, 5, 10 e 15%) sobre as propriedades catalíticas de óxido de ferro suportado em carvão ativado, preparado a partir de cascas de coco. O teor de ferro afetou as propriedades texturais e redutoras dos sólidos. Detectou-se hematita na amostra mais pobre em ferro e magnetita com um núcleo de hematita nas demais. Estes catalisadores foram eficazes na remoção do azul de metileno em soluções aquosas por adsorção e pela reação de Fenton. O sólido com 15% de ferro foi o mais ativo, provavelmente devido à maior quantidade de sítios ativos na superfície. Estes catalisadores são ambientalmente amigáveis, contribuindo para a redução de resíduos sólidos no meio ambiente e purificação de efluentes têxteis, preservando os recursos hídricos.Fil: Lima, Sirlene B.. Universidade Federal da Bahia, Instituto de Química; Brasil. Universidade Estadual de Campinas; BrasilFil: Borges, Sarah Maria. Universidade Estadual de Campinas; Brasil. Instituto de Ciência e Tecnologia de Materiais Complexos Funcionais. Instituto de Química; BrasilFil: Rangel. Maria do Carmo. Universidade Estadual de Campinas; Brasil. Universidade Federal Da Bahia; BrasilFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - la Plata. Centro de Investigación y Desarrollo En Ciencias Aplicadas "dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Cs.exactas. Centro de Investigación y Desarrollo En Ciencias Aplicadas ; Argentin

Phosphorus as a promoter of a nickel catalyst to obtain 1-phenylethanol from chemoselective hydrogenation of acetophenone

Two catalysts were prepared using monodisperse pre-synthetized nanoparticles of metallic nickel and nickel phosphides with the same average diameter. Both nanoparticles species were deposited on the same support: mesoporous silica nano-spheres of MCM-41. This support is suitable to inhibit agglomeration and sintering processes during preparation steps. Therefore, two supported and activated catalysts with the same average nanoparticles diameter were obtained. They differ only in the nature of the active species: metallic nickel and nickel phosphides. The effect of the presence of a second element (phosphorus), more electronegative than nickel, on the activity and selectivity in the chemoselective hydrogenation of acetophenone was studied. The reaction conditions were: H2 pressure of 1 MPa, 80 °C using n-heptane as solvent. With the aim to understand the catalytic results, nanoparticles, support and catalysts were carefully characterized by X-ray diffraction, diffuse light scattering, transmission electron microcopy, high resolution transmission electron microcopy, selected area electron diffraction, scanning electron microcopy, Fourier transformer infrared spectroscopy, N2 adsorption at -196 °C, atomic absorption, H2 and CO chemisorption and volumetric oxidation. Considering these results and geometric and electronic characteristics of the surface of both active species, a change in the adsorption intermediate state of acetophenone in presence of phosphorus is proposed to explain the hydrogenation chemoselectivity of nickel phospides.Fil: Costa, Dolly Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Soldati, Analía Leticia. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología; ArgentinaFil: Bengoa, Jose Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Marchetti, Sergio Gustavo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Vetere, Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; Argentin

Effect of iron content on the catalytic properties of activated carbon-supported magnetite derived from biomass

In recent times, the intense human activity has led to an increase of the agriculture wastes in the environment. "In order to find new applications for these materials, the effect of iron content (2.5, 5, 10 and 15%) on the catalytic properties of activated carbon-supported iron oxide, prepared from coconut shells, was studied. The iron amount affected the textural and reducing properties of the solids and particle sizes. Hematite was found for the most iron-poor sample, while particles of magnetite with a core of hematite were found for the others. These catalysts were effective in the methylene blue removal from aqueous solutions by adsorption and Fenton reaction. The solid with 15% of iron was the most active one probably due to the highest iron amount on the surface. These catalysts are environmentally friendly, contributing to the decrease of the solid wastes in the environment as well as to purify textile effluents, preserving water resources.Nos últimos tempos, a intensa atividade humana levou a um aumento de resíduos agrícolas no meio ambiente. Visando a encontrar novas aplicações para estes materiais estudou-se, neste trabalho, o efeito do teor de ferro (2.5, 5, 10 e 15%) sobre as propriedades catalíticas de óxido de ferro suportado em carvão ativado, preparado a partir de cascas de coco. O teor de ferro afetou as propriedades texturais e redutoras dos sólidos. Detectou-se hematita na amostra mais pobre em ferro e magnetita com um núcleo de hematita nas demais. Estes catalisadores foram eficazes na remoção do azul de metileno em soluções aquosas por adsorção e pela reação de Fenton. O sólido com 15% de ferro foi o mais ativo, provavelmente devido à maior quantidade de sítios ativos na superfície. Estes catalisadores são ambientalmente amigáveis, contribuindo para a redução de resíduos sólidos no meio ambiente e purificação de efluentes têxteis, preservando os recursos hídricos.Facultad de Ciencias ExactasCentro de Investigación y Desarrollo en Ciencias Aplicada

The effect of the starting material on the thermal decomposition of iron oxyhydroxides

The effect of the iron precursor on the thermal decomposition of iron oxyhydroxides was studied by DSC, DTA and TG in this work. Samples were prepared from iron nitrate, iron sulfate and iron chloride and the thermal curves obtained were analyzed by specific area measurements, X-ray diffraction and Mössbauer spectroscopy. It was found that the iron oxyhydroxide precursors affect the temperatures of the hematite formation as well as the textural properties of the final hematite producing particles with different diameters as following: iron sulfate (3.3 nm)&lt;&lt;iron nitrate (15 nm)&lt;iron chloride (24 nm).Centro de Investigación y Desarrollo en Ciencias Aplicada

Síntesis de nanoparticulas de Ni2P : Su aplicación como fase activa en reacciones de hidrogenación

En los últimos años se han comenzado a estudiar las propiedades catalíticas de los fosfuros de metales de transición, principalmente en reacciones de hidrodesulfurización e hidrodeoxigenación. Sin embargo, los estudios de reacciones de hidrogenación selectiva empleando estas fases son prácticamente inexistentes. El objetivo del presente trabajo es investigar las propiedades del fosfuro de níquel (Ni2P) como fase activa para la hidrogenación quimioselectiva de acetofenona. Debido a que muchos estudios han demostrado que la morfología de las partículas de Ni2P afecta la performance catalítica, nos hemos propuesto utilizar nanopartículas (NPs) de Ni2P presintetizadas con una estrecha distribución de tamaño de partícula.Facultad de Ciencias Exacta

Síntesis de nanoparticulas de Ni2P : Su aplicación como fase activa en reacciones de hidrogenación

En los últimos años se han comenzado a estudiar las propiedades catalíticas de los fosfuros de metales de transición, principalmente en reacciones de hidrodesulfurización e hidrodeoxigenación. Sin embargo, los estudios de reacciones de hidrogenación selectiva empleando estas fases son prácticamente inexistentes. El objetivo del presente trabajo es investigar las propiedades del fosfuro de níquel (Ni2P) como fase activa para la hidrogenación quimioselectiva de acetofenona. Debido a que muchos estudios han demostrado que la morfología de las partículas de Ni2P afecta la performance catalítica, nos hemos propuesto utilizar nanopartículas (NPs) de Ni2P presintetizadas con una estrecha distribución de tamaño de partícula.Facultad de Ciencias Exacta