Examinando por Autor "Builes S."
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Ítem Adsorption of Cadmium Using Biochars Produced from Agro-Residues(American Chemical Society, 2020-01-01) López J.E.; Builes S.; Heredia Salgado M.A.; Tarelho L.A.C.; Arroyave C.; Aristizábal A.; Chavez E.; Universidad EAFIT. Departamento de Ingeniería Mecánica; Bioingeniería GIB (CES – EAFIT)Biochars have been shown as promising materials for cadmium remediation. However, the different precursors and the pyrolysis process operating conditions can yield very different surface functional groups, and as a result, different cadmium sorption mechanisms can be observed in biochars. Herein we present the results of cadmium sorption on biochars produced from the pyrolysis of different agro-residues, namely, coffee husk, quinoa straw, and oil palm kernel shell. The adsorption isotherms were used to determine the influence of the biochar's physicochemical characteristics to their sorption behavior. The biochars prepared from quinoa residues showed much higher cadmium uptakes than the other biochars. The concentration of base cations was found to be a critical factor for cadmium sorption. Although the quinoa biochars presented large uptakes, it was found that base cations were supported on the biochars and could be removed by leaching. Results from this study suggest that concentration of base cations on biochars could be used as predictors of the biochar capabilities for the removal of cadmium in aqueous solution. Copyright © 2020 American Chemical Society.Ítem Adsorption of Cadmium Using Biochars Produced from Agro-Residues(American Chemical Society, 2020-01-01) López J.E.; Builes S.; Heredia Salgado M.A.; Tarelho L.A.C.; Arroyave C.; Aristizábal A.; Chavez E.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosBiochars have been shown as promising materials for cadmium remediation. However, the different precursors and the pyrolysis process operating conditions can yield very different surface functional groups, and as a result, different cadmium sorption mechanisms can be observed in biochars. Herein we present the results of cadmium sorption on biochars produced from the pyrolysis of different agro-residues, namely, coffee husk, quinoa straw, and oil palm kernel shell. The adsorption isotherms were used to determine the influence of the biochar's physicochemical characteristics to their sorption behavior. The biochars prepared from quinoa residues showed much higher cadmium uptakes than the other biochars. The concentration of base cations was found to be a critical factor for cadmium sorption. Although the quinoa biochars presented large uptakes, it was found that base cations were supported on the biochars and could be removed by leaching. Results from this study suggest that concentration of base cations on biochars could be used as predictors of the biochar capabilities for the removal of cadmium in aqueous solution. Copyright © 2020 American Chemical Society.Ítem Analysis of CO2 adsorption in amine-functionalized porous silicas by molecular simulations(American Chemical Society, 2015-06-01) Builes S.; López-Aranguren, P.; Fraile, J.; Vega, L.F.; Domingo, C.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosWe present the results of a combined experimental-molecular simulations approach concerning the capacity for CO2 adsorption of aminosilica hybrid products synthesized using supercritical fluids. Two porous supports were examined for amine functionalization, an ordered mesoporous silica (MCM-41) and a disordered silica gel (SG40). The textural properties of the studied materials were analyzed by low-temperature N2 adsorption-desorption isotherms and compared to those of molecular simulations using the grand canonical Monte Carlo simulation method. The CO2 adsorption capacity of these materials was evaluated by recording CO2 adsorption isotherms up to 100 kPa. Molecular simulations of the CO2 adsorption behavior of selected samples were performed to gain a fundamental understanding of the effect of functionalization. This study shows that in the functionalized materials, the distance between nitrogen atoms of the grafted amines is a critical factor for the occurrence of CO2 chemisorption, providing some insight into key parameters for designing adsorbent materials for CO2 capture and separation. The relationship between the adsorption results with N2 and CO2 allow us to compare the potential applications of the materials in CO2 adsorption and separation processes. A correlation of the N2 adsorption at a given pressure with the CO2 adsorption at a different pressure allowed the prediction of which materials will perform well for these processes. The hybrid products with high amine density have desirable features required for industrial sorbents, such as an enhanced CO2 adsorption capacity and selectivity. © 2015 American Chemical Society.Ítem A Comparative Assessment of Emerging Solvents and Adsorbents for Mitigating CO2 Emissions From the Industrial Sector by Using Molecular Modeling Tools(Frontiers Media S.A., 2020-01-01) Bahamon D.; Alkhatib I.I.I.; Alkhatib N.; Builes S.; Sinnokrot M.; Vega L.F.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosThe possibilities offered by molecular modeling tools to obtain relevant data at process conditions, while also gaining molecular insights on the techniques used for CO2 capture and separation, are presented here using selected case studies. Two different technologies, absorption with amine-based systems and adsorption on porous materials, were explored, using the molecular-based equation of state, soft-Statistical Associating Fluid Theory (SAFT), and Grand Canonical Monte Carlo simulations, respectively. The aqueous monoethanolamine (MEA) system was set as the benchmark for absorption and compared to the performance of 8 alternative amine-based systems, while 16 adsorbents belonging to different families (zeolites, metal–organic frameworks, amorphous silicas, and activated carbons), bare or functionalized with alkylamines, were investigated for the separation of CO2 by adsorption. In addition to obtaining molecular information on the CO2 capture process, the models were further used to examine the CO2 capture performance in terms of cyclic working capacity and energy index as key performance indicators, allowing the identification of promising systems that can improve the current ones to be further evaluated for separation in non-power industries. Results show that for the same total amine mass concentration, non-aqueous amine solvents have a 5–10% reduction in cyclic working capacity, and a 10–30% decrease in the energy index compared to their aqueous counterparts due to their lower heat of vaporization and specific heat capacity. In addition, M-MOF-74, NaX, and NaY structures present the best results for adsorption in temperature swing adsorption (TSA) processes. Similar values of energy requirements to those of amine-based systems (2–2.5 MJ kg CO2–1) were obtained for some of the adsorbent; however, the disadvantage of the TSA process versus absorption should be considered. These results confirm the reliability of molecular modeling as an attractive and valuable screening tool for CO2 capture and separation processes. © Copyright © 2020 Bahamon, Alkhatib, Alkhatib, Builes, Sinnokrot and Vega.Ítem Hybrid aminopolymer-silica materials for efficient CO2 adsorption(ROYAL SOC CHEMISTRY, 2015-01-01) López-Aranguren, P.; Builes S.; Fraile, J.; López-Periago, A.; Vega, L.F.; Domingo, C.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosThe present work focuses on the development of a new eco-efficient chemical method for the polymerization of aziridine to hyperbranched polyethyleneimine (PEI) into mesoporous silica by using compressed CO2 as a solvent, reaction medium and catalyst. PEI was in situ grafted into MCM-41 and silica gel substrates, with pore diameters of 3.8 and 9.0 nm, respectively. The optimal polymerization conditions were found by varying the reaction pressure (1.0-10 MPa), temperature (25-45°C) and time (20-400 min). The thermal stability analysis indicated that aminopolymer chains were covalently attached on the amorphous silica surface. The described compressed CO2 route for the synthesis of high amine content hybrid products (6-8 mmolN g-1) is a very fast method, with processing times in the order of few minutes even at very low working pressures (1.0 MPa), being a step forward in the design of efficient hybrid aminopolymer nanocomposites for CO2 capture. The adsorptive behavior of the prepared hybrid materials was experimentally established by recording the N2 (-196°C) and CO2 (25, 50 and 75°C) adsorption isotherms. Results were compared to molecular simulation studies performed using Grand Canonical Monte Carlo for either N2 or CO2 adsorbed on amino modified MCM-41, thus helping to elucidate the predominant PEI configuration present in the functionalized materials. © The Royal Society of Chemistry 2015.Ítem Predictions of fluidities of amines by molecular simulations: TraPPE-EH vs. OPLS-AA(Elsevier B.V., 2018-05-25) Rendón-Calle A.; Orozco G.A.; Builes S.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosAmines have several important industrial properties and commercial applications, such as gas sweetening and carbon capture; and the synthesis of: tranquilizers, decongestants, and azo dyes. For the design of many engineering applications, it is important to calculate the density and viscosity of the substances in order to determine how the fluids should be handled, stored, and discarded. In this work, the accuracy of two common force fields for amines, TraPPE-EH and OPLS-AA, was evaluated with respect to their predictions of liquid densities and fluidities for a large set of amine molecules including primary, secondary and tertiary. We propose the use of the reciprocal of viscosity, the fluidity, as a more accurate assessment of the predictions of viscosity at different temperatures. The fluidity was calculated using molecular dynamics in the isothermal-isobaric ensemble (NPT) along with the Green Kubo formalism. The simulation results were compared to available experimental information in order to provide a quantitative study of the force fields accuracy as well as their transferability to amines and thermodynamic conditions different to the ones used in their original parametrization. Overall, liquid densities and fluidities are well reproduced by the TraPPE-EH force field with absolute average deviations of 1.5% and 12%, respectively. However, important deviations were found for the OPLS-AA force field corresponding to 3.6% and 28% for density and fluidity respectively. In order to obtain better estimations of the fluidity, a temperature correction that accounts for the error in the liquid density predictions was proposed. Once the temperature correction was included the average deviation of the fluidity decreased to 10% for TraPPE-EH and to 18% for OPLS-AA. © 2018 Elsevier B.V.Ítem Substantial improvement of electrocatalytic predictions by systematic assessment of solvent effects on adsorption energies(Elsevier B.V., 2020-01-01) Rendón-Calle A.; Builes S.; Calle-Vallejo F.; Universidad EAFIT. Departamento de Ingeniería de Procesos; Desarrollo y Diseño de ProcesosElectrocatalytic activities are largely determined by the interplay of adsorbates with substrates and solvents. Although capturing the interactions of those three components is usually arduous, here we provide a simple micro-solvation method to evaluate them in aqueous media. The method helps determine: (a) the number of water molecules making hydrogen bonds with the adsorbates, and (b) the energetic stabilization of the adsorbates by those hydrogen bonds. To evaluate the usefulness of the method, we consider CO2 reduction to CO, CH4, and CH3OH on Cu, Ag, Au, and Zn. Applying the calculated solvation corrections, we find good agreement with experiments in the predicted pathways and onset potentials, with an average error of only 0.07 V. Conversely, models with ad hoc or implicit solvation corrections predict unlikely pathways and onset potentials with considerably larger errors. These results indicate that accurate methods to assess solvent-adsorbate interactions contribute to improve computational electrocatalysis models. © 2020 Elsevier B.V.