Open Access
Structure and activity of nickel supported on hibonite-type La-hexaaluminates synthesized from aluminum saline slags for the dry reforming of methane
(Elsevier, 2021) Torrez Herrera, Jonathan Josué; Korili, Sophia A.; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Zientziak; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This work describes the procedures followed to obtain four hibonite-type La-hexaaluminates (La-HA) using aluminum saline slag waste as the aluminum source. Briefly, an acid-extracted aluminum solution (8.9 gAl/L) was used to synthesize the hexaaluminate by mixing with a stoichiometric amount of lanthanum nitrate and 2-propanol/polyethylene glycol/methanol/1-hexanol/glucose depending on the hydrothermal conditions of the synthesis. The results showed the formation of pure-phase hexaaluminate at 1473 K in all cases, with differences in the textural properties between the materials. The solids obtained were used as supports for nickel catalysts (10 wt.%) for the dry reforming of methane (DRM) at 973 K. The supports and catalysts were characterized by X-ray diffraction (XRD), N2 adsorption at 77 K, X-ray fluorescence (XRF), temperature-programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). An effect of the textural properties, dispersión of the metallic phase and nickel-support interaction on the performance of the catalyst was found. Our results also show a new application of a catalyst synthesized from an industrial waste such as aluminum saline slags.
Open Access
Bimetallic (Pt-Ni) La-hexaaluminate catalysts obtained from aluminum saline slags for the dry reforming of methane
(Elsevier, 2021) Torrez Herrera, Jonathan Josué; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This work describes the synthesis of platinum-nickel/lanthanum hexaaluminates (PtNi/LHA) and their performance in terms of stability and catalytic activity in the dry reforming of methane (DRM) at 973 K. An Al solution (9.40 g/L) obtained from an Al saline slag waste by acid extraction was used to synthesize the hexaaluminate by mixing with a stoichiometric amount of lanthanum nitrate and methanol/Peg400/PegMn400 under hydrothermal conditions at 493 K for 16 h. After calcination at 1473 K for 2 h, the presence of LHA was confirmed. Wet impregnation of the synthesized support was used to obtain an initial Ni/LHA catalyst (10 wt% NiO) and the modified PtNi/LHA catalysts (0.2–1 wt% Pt). The support and catalysts were characterized by X-ray diffraction (XRD), N2 adsorption at 77 K, temperature- programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR- TEM). The analysis of the TPR patterns for the catalysts allowed the type of metal support interaction and NiO species to be determined, with a weak interaction with the support being observed in all cases. The presence of Pt promoted NiO reducibility. The PtNi/LHA catalysts synthesized were found to be active and very stable in the DRM reaction after reaction for 50 h. The catalytic behavior was evaluated from the CO2 and CH4 conversions, as well as the H2/CO selectivity, with values of between 89% and 92% in almost all the time range evaluated. The presence of Pt improved the stability and catalytic performance of Ni/LHA thus improving resistance to coke formation.
Embargo
Improvement of the adsorption properties of an activated carbon coated by titanium dioxide for the removal of emerging contaminants
(Elsevier, 2019) Taoufik, Nawal; Elmchaouri, Abdellah; Anouar, Fatna; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Three activated carbon coated titanium dioxide composites are evaluated as adsorbents for the removal of three pharmaceutical compounds: clofibric, gallic and salicylic acids from aqueous solutions. These composite materials are characterized by several techniques as SEM, FT-IR, TGA and point of zero charge determination. The adsorption mechanism of acids was investigated and compared to the adsorption on the virgin carbon. The analysis of adsorption isotherms and kinetic properties reveals that the addition of TiO2 increased the adsorption capacities of the initial material. The adsorption kinetics has been studied in terms of pseudo-first and pseudo-second order kinetic models, and the Freundlich, Langmuir, Temkin, Tôth and Sips isotherms models have also been applied to the equilibrium adsorption data. The analysis of results indicated that the adsorption of acids on the activated carbon-titanium dioxide composites is well described by the pseudo-first order kinetic model and the Sips isotherm equation fitted the sorption experimental results better than other models.
Open Access
Effect of the surface properties of Me2+/Al layered double hydroxides synthesized from aluminum saline slag wastes on the adsorption removal of drugs
(Elsevier, 2020) Santamaría Arana, Leticia; Devred, F.; Gaigneaux, E. M.; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua, PI017-PI039 CORRAL
This work presents the synthesis of Me2+ (Co, Mg, Ni and Zn)/Al layered double hydroxides (LDH) with a 3:1 M ratio by the co-precipitation method. Structural characterization and comparison of the series has been achieved using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at 77 K, thermogravimetry measurements (TGA), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), ammonia temperature-programmed desorption (NH3-TPD) and point of zero charge (pHpzc). Batch experiments were performed to analyze the adsorption capacity of the different LDH on diclofenac and salicylic acid, as example of emergent pollutants. The pH, mass of adsorbent, contact time and concentration of pollutant were the parameters used to compare the adsorption performance of the synthesized materials. Samples showed different behavior and the equilibrium was reached at different times, Mg6Al2 and Zn6Al2 showed lower equilibrium times but had higher adsorption capacity. Various adsorption and isotherm equation models were employed to study both the kinetic and equilibrium results and, in general, the removal of diclofenac was greater than that of salicylic acid. 1-Butanol conversion was also used as a means of acidity and basicity characterization and the results were compared with the adsorption performance of the samples in order to explain the results found. A relationship between the amount of pollutants adsorbed and the butenes formed in the dehydrogenation reaction of 1-butanol was found.
Open Access
Progress and perspectives in the catalytic hydrotreatment of bio-oils: effect of the nature of the metal catalyst
(American Chemical Society, 2024) Gil Bravo, Antonio; Sancho Sanz, Iris; Korili, Sophia A.; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
In recent years, there has been a surge of interest in transforming biomass into fuel, driven by its potential as the only realistic renewable carbon resource. Several conversion methods have been explored to achieve this, including gasification for producing synthesis gas, fast pyrolysis or hydrothermal liquefaction for obtaining bio-oils, and hydrolysis for generating aqueous sugars. Bio-oils offer environmental benefits due to their lower CO2 emissions, but their direct use as fuels is hindered by limitations such as thermal instability, high viscosity and acidity, and low calorific value. Consequently, advancements in treatment methods are necessary before bio-oils can be used as direct fuels. This review focuses on the catalytic hydrotreatment of bio-oils, which has been shown to be an effective approach for the removal of heteroatoms at moderate temperatures (between 300 and 450 °C) but at high pressures (up to 20 MPa). Oxygenated compounds are transformed into H2O, and N and S are transformed into NH3 and H2S, respectively. The analysis examines how process temperature, residence time, hydrogen pressure, solvent selection, and type of catalyst influence the properties of the improved bio-oil. Mo/W sulfide-supported catalysts have been traditionally used as active phases in hydrotreatment processes, as the presence of S limits catalyst deactivation, while the presence of Ni or Co as promoters enhances hydrogenation reactions. New research trends are exploring alternative catalyst formulations, such as metal phosphides, carbides, nitrides, and mesoporous materials as supports with controlled acid-basic properties.
Open Access
Application of industrial wastes from chemically treated aluminum saline slags as adsorbents
(American Chemical Society, 2018) Gil Bravo, Antonio; Arrieta Chango, Ekhine; Vicente, Miguel Ángel; Korili, Sophia A.; Institute for Advanced Materials and Mathematics - INAMAT2
In this study, industrial wastes, which remain after aluminum extraction from saline slags, were used as adsorbents. The aluminum saline slags were treated under reflux with 2 mol/dm3 aqueous solutions of NaOH, H2SO4, and HCl for 2 h. After separation by filtration, aqueous solutions containing the extracted aluminum and residual wastes were obtained. The wastes were characterized by nitrogen adsorption at -196 °C, X-ray diffraction, scanning electron microscopy, and ammonia pulse chemisorption. The chemical treatment reduced the specific surface area, from 84 to 23 m2/g, and the pore volume, from 0.136 to 0.052 cm3/g, of the saline slag and increased the ammonia-adsorption capacity from 2.84 to 5.22 cm3/g, in the case of acid-treated solids. The materials were applied for the removal of Acid Orange 7 and Acid Blue 80 from aqueous solutions, considering both single and binary systems. The results showed interesting differences in the adsorption capacity between the samples. The saline slag treated with HCl rapidly adsorbed all of the dyes present in solution, whereas the other materials retained between 50 and 70% of the molecules present in solution. The amount of Acid Orange 7 removed by the nontreated material and by the material treated with NaOH increased in the presence of Acid Blue 80, which can be considered as a synergistic behavior. The CO2 adsorption of the solids at several temperatures up to 200 °C was also evaluated under dry conditions. The aluminum saline slag presented an adsorption capacity higher than the rest of treated samples, a behavior that can be explained by the specific sites of adsorption and the textural properties of the solids. The isosteric heats of CO2 adsorption, determined from the Clausius-Clapeyron equation, varied between 1.7 and 26.8 kJ/mol. The wastes should be used as adsorbents for the selective removal of organic contaminants in wastewater treatment.
Open Access
Understanding the formation of Al13 and Al30 polycations to the development of microporous materials based on Al13-and Al30-PILC montmorillonites: a review
(Elsevier, 2021) Cardona Rodríguez, Yaneth; Gil Bravo, Antonio; Korili, Sophia A.; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Hydrolysis of aluminum cations (Al3+), the third most abundant metal in the Earth’s crust, is considered relevant in many academic fields, including materials science and chemical engineering. AlIII -polycations and their different uses have also been widely studied, as reflected in the extensive literature in that field. This review summarizes some of those studies, from Al3+ hydrolysis to form Al13 ([Al13O4(OH)24(H2O)12]7+) and Al30 ([(Al30O8(OH)56(H2O)24)]18+) polycations and their specific use as pillaring agents for montmorillonite, which is the most commonly used clay mineral in Aluminum Pillared Interlayered Clays (Al-PILC) synthesis. The experimental conditions published over the years regarding the synthesis of both these AlIII-polycations, as well as the conditions employed to synthesize Al-PILC montmorillonite using Al13 and Al30 polycation solutions, are also summarized. This review highlights some of the findings that have made it possible to explain the formation of Al13- and Al30-PILC montmorillonites, and allow us to clearly understand their differences. Finally, the new tendencies in the development of these materials based on Al-PILC and the applications are also highlighted.
Open Access
Saline slag waste as an aluminum source for the synthesis of Zn–Al–Fe–Ti layered double-hydroxides as catalysts for the photodegradation of emerging contaminants
(Elsevier, 2020) Santamaría Arana, Leticia; Vicente, Miguel Ángel; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua, PI017-PI039 CORRAL
In this work, aluminum extracted from saline slag waste is valorized to create a layered double-hydroxide series containing zinc and various proportions of aluminum/titanium. Materials were synthesized by the co-precipitation method with an Me2+/Me3+ molar ratio of 3:1 and tested for the removal of diclofenac and salicylic acid from water under UV radiation. The incorporation of 5 wt% iron by wet impregnation is evaluated. In addition, another series of zinc, aluminum/iron materials with and without 5 wt% impregnated titanium are tested as catalysts for comparison. Structural characterization and comparison of the two series was performed by powder X-ray diffraction (PXRD), nitrogen adsorption at 77 K, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. The uncalcinated samples had a typical hydrotalcite structure with a high crystallinity; the presence of ZnO, ZnFe2O4 or Fe3O4 was found after calcination. The specific surface areas of the dried samples ranged from 78 to 199 m2/g, being highest for Zn6Al0.5Ti1.5. Overall, the results showed that the ZnAlTi series were more effective catalysts than ZnAlFe for photodegradation of the emerging contaminants diclofenac and salicylic acid, under UV light at 298 K, considering two concentrations of the organic molecules (5 and 50 μmol/dm3).
Open Access
White and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites as catalysts for toluene photodegradation from aqueous solutions
(MDPI, 2019) Mora, Lucas D.; Trujillano, Raquel; Rives, Vicente; Pérez Bernal, María Elena; Korili, Sophia A.; Gil Bravo, Antonio; Faria, Emerson H. de; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The presence of volatile organic compounds in groundwater is a major concern when it is used as a drinking water source because many of these compounds can adversely affect human health. This work reports on the preparation and characterization of white and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites and their use as catalysts in the photochemical degradation of toluene, a significant volatile organic compound. The nanocomposites were prepared by a sol-gel procedure, using titanium bis(triethanolaminate)diisopropoxide as a precursor. Thermal treatments of the nanocomposites led to different polymorphic titania phases, while the clay changed from kaolinite to metakaolinite. This structural evolution strongly affected the photocatalytic degradation behavior-all the solids efficiently degraded toluene and the solid calcined at 400 degrees C, formed by kaolinite and anatase, showed the best behavior (90% degradation). On extending the photochemical treatment up to 48 h, high mineralization levels were reached. The advantage of photodegradation using the nanocomposites was confirmed by comparing the results from isolated components (titanium dioxide and kaolinite) to observe that the nanocomposites displayed fundamental importance to the photodegradation pathways of toluene.
Open Access
Hydrothermal liquefaction of biomass as one of the most promising alternatives for the synthesis of advanced liquid biofuels: a review
(MDPI, 2021) Grande López, Lucía; Pedroarena Apezteguía, Iván; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua
The use of biofuels offers advantages over existing fuels because they come from renewable sources, they are biodegradable, their storage and transport are safer, and their emissions into the atmosphere are lower. Biomass is one of the most promising sustainable energy sources with a wide variety of organic materials as raw material. Chemical, biochemical, and thermochemical methods have been proposed to obtain biofuels from raw materials from biomass. In recent years, a thermochemical method that has generated great interest is hydrothermal liquefaction. In this paper, a brief review of the main sources for liquid biofuels and the synthesis processes is presented, with special emphasis on the production of biofuels using hydrothermal liquefaction by using waste generated by human activity as raw material.