Batch and Column Studies for the Removal of Lead from Aqueous Solutions Using Activated Carbons from Viticultural Industry Wastes

Adsorption studies (kinetic, batch and dynamic assays) were carried out for lead removal from aqueous solutions using wastes from the wine industry. The adsorbents used were obtained from grape stalk and pomace.These materials were carbonized, briquetted and activated with steam. Addition of a leaching step before activation lowered the high ash content of the materials.The products were characterized by elemental and proximate analysis, point of zero charge pH, specific surface area, pore-size distribution, Fourier transform infrared spectroscopy and surface acidic and basic groups. Considering the physicochemical and textural properties of the adsorbents, a comparative analysis of the results was made. These solids showed a marked basic character; therefore, the pH was a very important variable in adsorption tests, and thus it was necessary to maintain the pH in a favourable range. Batch equilibrium assays showed that the tested adsorbents had good adsorption capacities, better than the ones reported previously for similar materials. In dynamic tests, the removal of lead by both activated carbon briquettes was good and attributed to the coupling of adsorption and precipitation as a result of the increase in the pH values, which could not be controlled.Fil: Deiana, A. C.. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Gimenez Guerrero, Marianela Gema. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Rómoli, Santiago. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Sardella, Maria Fabiana. Universidad Nacional de San Juan. Facultad de Ingenieria. Instituto de Ingenieria Quimica; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; Argentin

Evaluation of the dioxin and furan formation thermodynamics in combustion processes of urban solid wastes

Specific combustion programs (Gaseq, Chemical equilibria in perfect gases, Chris Morley) are used to model dioxin and formation in the incineration processes of urban solid wastes. Thanks to these programs, it is possible to establish correlations with the formation mechanisms postulated in literature on the subject. It was found that minimum oxygen quantities are required to obtain a significant formation of these compounds and that more furans than dioxins are formed. Likewise, dioxin and furan formation is related to the presence of carbon monoxide, and dioxin and furan distribution among its different compounds depends on the chlorine and hydrogen relative composition. This is due to the fact that an increased chlorine availability leads to the formation of compounds bearing a higher chlorine concentration (penta-, hexa-, hepta-, and octachlorides), whereas an increased hydrogen availability leads to the formation of compounds bearing a lower chlorine number (mono, di-, tri-, and tetrachlorides).Fil: Moreno Piraján, Juan Carlos. Universidad de los Andes; ColombiaFil: García Ubaque, C. A.. Universidad de los Andes; ColombiaFil: Fajardo, R.. Universidad de los Andes; ColombiaFil: Giraldo, L.. Universidad Nacional de Colombia; ColombiaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; Argentin

Pure niobia as catalyst for the oxidation of organic contaminants: Mechanism study via ESI-MS and theoretical calculations

In this work, synthetic and natural niobium oxide (niobia), were used to promote the oxidation of methylene blue dye. The samples were characterized by XRD, XPS and FTIR measurements. The presence of reactive species on the surface of the samples strongly increases the oxidation rate of the methylene blue dye. The reaction mechanism was studied by ESI-MS analyses. Moreover, kinetic data and XPS spectroscopy suggest that the oxidation of the organic dye involves oxidizing species mainly generated after previous treatment with H2O2. The results also showed that the oxidation takes place by a homolytic mechanism via radical intermediates.Fil: Oliveira, Luiz C. A.. Universidad Federal de Lavras; BrasilFil: Ramalho, Teodorico C.. Universidad Federal de Lavras; BrasilFil: Gonçalves, Maraísa. Universidad Federal de Lavras; BrasilFil: Cereda, Flávia. Universidad Federal de Lavras; BrasilFil: Carvalho, Kele T.. Universidad Federal de Lavras; BrasilFil: Nazzarro, Marcelo Sandro. Universidad Nacional de San Luis. Facultad de Ciencias Fisico Matematicas y Naturales. Departamento de Fisica. Laboratorio de Ciencias de Superficies y Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; ArgentinaFil: Sapag, Manuel Karim. Universidad Nacional de San Luis. Facultad de Ciencias Fisico Matematicas y Naturales. Departamento de Fisica. Laboratorio de Ciencias de Superficies y Medios Porosos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentin

Catalizadores de Ni-Co/Al2O3 obtenidos por Combustión de Matriz de Urea espontánea y controlada para producir H2 por APR de Glicerol

The aim is to improve the interaction and dispersion of Ni/Co in catalysts supported on γ-Al2O3 by controlling the temperature in the preparation by the urea matrix combustion method (CCMU). The resulting samples are used to obtain H2 by aqueous phase reforming (APR) of glycerol. Ni and Co nitrates are co-impregnated with urea, dried and fixed by heating with different temperature ramps (R1, R5 and R10) to obtain 1.5% Ni and 4.5% Co. The physicochemical properties are characterized by N2 sortometry and CO chemisorption. Its behavior is analyzed in APR of glycerol with 0.5 g of catalyst reduced at 500 ºC. Production and selectivity to H2, reaction stability and deactivation by coke are analyzed by temperature programmed oxidation (TPO). The CCMU-R10 catalyst shows improved H2 performance and greater metallic dispersion compared to the same catalyst prepared by spontaneous combustion, without temperature control, CMU. Controlling the combustion of urea improves the Ni/Co interaction, increasing the yield to H2 by 74%, with equal selectivity to H2 and CH4 and reducing the coke accumulated in the same period in APR of glycerol in the selected reaction conditions by 21%.Se busca mejorar la interacción y dispersión de Ni/Co en catalizadores soportados en γ-Al2O3 controlando la temperatura en la preparación por el método de combustión de matriz de urea (CCMU). Las muestras resultantes se utilizan para obtener H2 por reformado en fase acuosa (APR) de glicerol. Nitratos de Ni y Co son co-impregnados con urea, secados y fijados por calentamiento a diferentes rampas de temperatura (R1, R5 y R10) para obtener 1,5% Ni y 4,5% Co. Las propiedades fisicoquímicas son caracterizadas por sortometría de N2 y quimisorción de CO. Su comportamiento se analiza en APR de glicerol con 0,5 g de catalizador reducido a 500 ºC. Se analiza producción y selectividad a H2, estabilidad en reacción y desactivación por coque, mediante oxidación a temperatura programada (TPO). El catalizador CCMU-R10 muestra un rendimiento a H2 mejorado y mayor dispersión metálica respecto al mismo catalizador preparado por combustión espontánea, sin control de temperatura, CMU. Controlando la combustión de la urea se mejora la interacción Ni/Co incrementándose un 74% el rendimiento a H2, con igual selectividad a H2 y CH4 y reduciendo un 21% el coque acumulado en igual período en APR de glicerol en las condiciones de reacción seleccionadas

Fe/SBA-15: Characterization and its application to a heterogeneous solar photo-Fenton process in order to decolorize and mineralize an azo dye

Fe/SBA-15 catalyst with different iron (Fe) loads (6% and 10% wt.) was synthesized via incipient wetness impregnation. The potential photocatalytic properties were tested using solar radiation, as a novel catalyst in heterogeneous Fenton approach to degrade Methyl Orange azo dye. A partial pore blocking of the substrate by Fe nanoparticles was detected and the main form of Fe present was Fe2O3. When the Fe(10%)/SBA-15 catalyst was used for heterogeneous solar photo-Fenton reaction, total discoloration of the effluent was achieved in 90 min, and 89% of COD was removed in 240 min. Short-chain linear carboxylic acids were followed over time, as well as inorganic ions.Fil: Arroyo Gómez, José Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Toncón Leal, Cristian Fabian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: dos Santos, A.J.. Universidade Federal do Rio Grande do Norte; BrasilFil: Moreno, Mario S.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Martínez Huitle, C. A.. Universidade Federal do Rio Grande do Norte; Brasi

The endoxylanases from family 11: Computer analysis of protein sequences reveals important structural and phylogenetic relationships

Indexación: Scopus.Eighty-two amino acid sequences of the catalytic domains of mature endoxylanases belonging to family 11 have been aligned using the programs MATCHBOX and CLUSTAL. The sequences range in length from 175 to 233 residues. The two glutamates acting as catalytic residues are conserved in all sequences. A very good correlation is found between the presence (at position 100) of an asparagine in the so-called 'alkaline' xylanases, or an aspartic acid in those with a more acidic pH optimum. Four boxes defining segments of highest similarity were detected; they correspond to regions of defined secondary structure: B5, B6, B8 and the carboxyl end of the alpha helix, respectively. Cysteine residues are not common in these sequences (0.7% of all residues), and disulfide bridges are not important in explaining the stability of several thermophilic xylanases. The alignment allows the classification of the enzymes in groups according to sequence similarity. Fungal and bacterial enzymes were found to form mostly separate clusters of higher similarity.https://www.sciencedirect.com/science/article/pii/S0168165602000020?via%3Dihu

Adsorption of CO2 on Amine-Grafted Activated Carbon

Adsorption on amine-grafted materials may be a potentially attractive alternative to capturing CO2 from power plants. Activated Carbon (AC) has been proposed as a potential adsorbent due to its natural affinity for CO2 and to the possibility of tailoring textural properties and surface chemistry to enhance capacity and selectivity. An AC commercial sample was functionalized with monoethanolamine (MEA) in order to obtain nitrogen-enriched AC with two different loadings (ACN10 and ACN20). Samples characterization was carried out by nitrogen adsorption/desorption isotherms at 77 K, XPS, FTIR and adsorption microcalorimetry. CO2 equilibrium adsorption experiments were accomplished in a volumetric system in the pressure range of vacuum up to 10 bar, at 298 and 348 K. Impregnated activated carbon presented different chemical and textural characteristics with a significant reduction in the surface area, depending on the amine loading. A high adsorption capacity at room temperature and high pressure was observed for the pristine AC as compared to the modified samples. The reduction in surface area affected the adsorption capacity of CO2 at 298 and 348 K, except for adsorption on ACN10 at 348 K, which suggests the occurrence of chemisorption.Fil: Bezerra, Diôgo P.. Universidade Federal do Ceara. Department of Chemical Engineering. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Da Silva, Francisco W. M.. Universidade Federal do Ceara. Department of Chemical Engineering. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: de Moura, Pedro A. S.. Universidade Federal do Ceara. Department of Chemical Engineering. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; ArgentinaFil: Vieira, Rodrigo S.. Universidade Federal do Ceara. Department of Chemical Engineering. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Rodriguez Castellon, Enrique. Universidad de Malaga. Facultad de Ciencias; EspañaFil: de Azevedo, Diana C. S.. Universidade Federal do Ceara. Department of Chemical Engineering. Grupo de Pesquisa em Separações por Adsorção; Brasi

Kaolinite-based zeolites synthesis and their application in CO2 capture processes

In light of the urgent need of reducing the atmospheric CO2 emissions, the use of low-cost adsorbents, that exhibit a high affinity and CO2 adsorption capacity, is a promising method from the economic and environmental point of view to separate CO2 from the flue gas emitted from large sources of emissions like power-fueled plants. Clay minerals are low-cost raw materials with high availability all over planet and great versatility in the fields of adsorption and catalysis processes. The present study pretends to elucidate the link between the reaction conditions during the synthesis of the zeolite from kaolinite and its CO2 adsorption capacity. For that purpose, the type A zeolite was synthesized via hydrothermal process in alkaline solution using metakaolinite as a starting material. The metakaolinite was obtained by calcination of kaolinite at 600 degrees C and some parameters such as temperature and synthesis time were modified to optimize the synthesis aiming for a high CO2 adsorption capacity adsorbent. Synthesized materials were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), N-2 adsorption-desorption at -196 degrees C and CO2 adsorption at 0 degrees C (up to 10 bars) isotherms and Nuclear Magnetic Resonance of solids (NMR). In addition, the adsorption capacity of CO2 was evaluated by means of CO2 adsorption-desorption isotherms at 25 degrees C up to atmospheric pressure. The obtained results indicated that synthesized zeolite 4A can be successfully prepared from natural kaolinite (via metakaolinization) at 100 degrees C for 48 h under alkaline conditions, showing chemical and physical properties similar to that of the commercial 4A zeolite

Improvement in the Adsorption of Anionic and Cationic Dyes From Aqueous Solutions: A Comparative Study Using Aluminium Pillared Clays and Activated Carbon

The aim of this work was to evaluate the adsorption properties of anionic dye Reactive Black 5 (RB5) and cationic dye Methylene Blue (MB) from salted aqueous solution using natural clay, aluminum pillared clay (Al-PILC), and activated carbon. The textural properties of the materials were obtained by N2 adsorption at 77 K and the structural properties of natural and pillared clays were determined by X-ray diffraction. The effect of pH, contact time, initial concentration of dye, and influence of the addition of NaCl were evaluated by batch adsorption. Adsorption isotherms of Al-PILC, in different salt concentration were compared with natural clay and activated carbon. The adsorption isotherms were well fitted by the Langmuir and Langmuir-Freundlich models. The process of pillaring only improved the adsorption of the anionic dye RB5. Depending on the system adsorbent/adsorbate analyzed, the salt concentration can either help or hinder dye adsorption. We found that a special morphology formed during the process of pillaring greatly increased adsorption of the MB cationic dye in the range of high salt concentrations. This unexpected result may help in developing new pillarization strategies to treat effluents with high salt content.Fil: Aguiar, J. E.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Bezerra, B. T. C.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Siqueira, A. C. A.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Barrera Diaz, Deicy Amparo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Física Aplicada; ArgentinaFil: Azevedo, D. C. S.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Lucena, S. M. P.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; BrasilFil: Silva Jr., I. J.. Universidade Federal do Ceará. Centro de Tecnologia. Departamento de Engenharia Química. Grupo de Pesquisa em Separações por Adsorção; Brasi

Influencia de las Propiedades Texturales en la Adsorción de Hidrógeno en Materiales Nanoestructurados Mesoporosos Tipo MCM-41

El hidrógeno es un importante vector energético capaz de sustituir el uso de combustibles fósiles en la actualidad. Uno de los principales inconvenientes para la implementación de sistemas que emplean hidrógeno es su almacenamiento. Actualmente, existen investigaciones en curso con el fin de desarrollar materiales para ser empleados en sistemas de almacenamiento, como por ejemplo materiales formadores de hidruros y materiales porosos que almacenan hidrógeno por adsorción. En este trabajo se sintetizaron materiales MCM-41 por síntesis hidrotérmica con relación Si/Ni = 20 y 60 y tiempos de síntesis de 0 a 7 días. Se estudió la influencia del tiempo de síntesis en las propiedades estructurales y texturales de los materiales, y se evaluó la adsorción de hidrógeno y el efecto de incorporar níquel en su estructura para mejorar el almacenamiento. Los materiales fueron caracterizados mediante adsorción-desorción de N2 a 77 K, difracción de rayos X, microscopía electrónica de transmisión y espectroscopia ultravioleta visible con reflectancia difusa