Open Access
Development of ceramic-MOF filters from aluminum saline slags for capturing CO2
(Elsevier, 2023) Torrez Herrera, Jonathan Josué; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This study describes the procedures followed to synthesize ceramic-MOF filters using aluminum saline slag wastes. Briefly, the raw aluminum saline slags were washed at 80 ◦C to significantly reduce the saline content and eliminate gases. The pretreated material was mixed with glucose (G/S ratios between 0.2 and 1.6) and acetone by stirring for 4 h. After this time, the resulting solid was dried at 60 ◦C and then at 190 ◦C. During the glucose caramelization step, PegMn400 was also added and the temperature increased to 1200 ◦C. The obtained solid was impregnated with precursor solutions to achieve a supported ZIF-8 MOF. The ceramic-MOF filters were characterized by X-ray diffraction (XRD), N2 adsorption at 77 K, X-ray fluorescence (XRF), scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM), thereby confirming the presence of a structure that allows dispersion of the synthesized and supported ZIF-8. Finally, the performance of these ceramic-MOF filters as CO2 adsorbents was evaluated in the temperature range 50–300 ◦C, with isosteric heats of 19 kJ/mol being obtained using the Clausius-Clapeyron equation.
Open Access
Catalytic valorization of CO2 by hydrogenation: current status and future trends
(Taylor and Francis, 2021) Sancho Sanz, Iris; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Terrestrial environmental and biological systems are being threatened by the tremendous amount of human carbon dioxide emissions. Therefore, it is crucial to develop a sustainable energy system based on CO2 as chemical feedstock. In this review, an introduction to the CO2 activation and transformation has been made, together with a more comprehensive study of the catalytical reduction of CO2 to methane, methanol, and formic acid, which are currently contemplated as chemical feedstocks and/or promising energy carriers and alternative fuels.
Open Access
Effect of the synthesis method on the morphology, textural properties and catalytic performance of La-hexaaluminates in 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 nickel/lanthanum hexaaluminates (NiO/LHA), optimizing the LHA synthesis method, as well as their performance in terms of stability and catalytic activity in the dry reforming of methane (DRM). The synthesis methods studied include co-precipitation, nitrate decomposition and freeze drying, using a La/Al molar ratio of 1:11 in all methods. Drying methods, namely oven drying (4 h at 353 K), vacuum drying (8 h at 353 K) + oven drying (2 h at 423 K) and heat treatment (12 h at 473 K) + oven drying (2 h at 373 K), were also optimized during selection of the final catalyst support. After calcination at 1473 K for 2 h, the presence of lanthanum aluminate (LaAlO3) and traces of LHA were found in all cases. Specific surface areas of 50, 32 and 30 m(2)/g were obtained for the samples AD1 (nitrate decomposition), FD1 (freeze drying), CP1 (co-precipitation). The nitrate decomposition method was selected and optimized to obtain the LHA structure at low temperature in the presence of Ni(II), using a La/Al/Ni molar ratio of 1/15/0.2. The results showed the formation of pure-phase hexaaluminate at 1473 K. The solids obtained were used as supports for nickel catalysts (10 wt%) for DRM at 973 K. The supports and catalysts were characterized by X-ray diffraction (XRD), N-2 adsorption at 77 K, temperature-programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The simulation of the TPR patterns of the catalysts allowed determining the type of metal support interaction and the activation energy of the system as well as the rest of the kinetic parameters. A cumulative mean activation energy of 100.7 kJ/mol was determined for the catalysts. The metallic morphologies, dispersion and distribution of NiO on the surface of the LHA support were analyzed considering a theoretical simulation of the reduction profiles, obtaining an average growth factor of 1.4, which indicates that the metallic phase is growing in one and two dimensions. The NiO/LHA catalysts synthesized were found to be active and very stable in the DRM reaction after 20 h of reaction with an average selectivity H-2/CO upper than 0.90. The differences observed can be related to the textural properties developed during the optimized nitrate decomposition method. The characterization analysis by simulation, TPR, XRD, TEM, SEM allowed us to establish the effect of the textural properties, the metal interaction, the growth of the nickel grains and their distribution in the support on the catalytic performance in DRM. The better performance was obtained with the catalysts with higher porosity and greater support metal interaction, which allowed obtaining a better distribution of the metallic phase, thus generating less harmful carbonaceous species for the activity of the catalyst and therefore showing the best values of catalytic stability and conversion. Finally, three types of coke were identified from HR-TEM and EDS analysis: graphitic, filamentous and CNT, showing different effects on the catalytic behavior deactivation being the presence of graphitic more aggressive than the other two species.
Open Access
Optimizing the removal of nitrate by adsorption onto activated carbon using response surface methodology based on the central composite design
(Taylor & Francis, 2020) Taoufik, Nawal; Elmchaouri, Abdellah; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
This study sheds light on the adsorption process for the removal of nitrate ions from synthetic aqueous solutions. This contaminant pose a potential risk to the environment and can cause health effects including cancers and methemoglobinemia in infants. When the adsorption process is carried out, the effect by the several operating parameters such as initial nitrate concentration, pH, mass of activated carbon, and contact time becomes apparent. The essential process variables are optimized using response surface methodology (RSM) based on the central composite design (CCD) experiments. For this purpose 31 experimental results are required to determine the optimum conditions. The optimum conditions for the removal of nitrates is found to be: initial nitrate concentration = 15 mg/L; initial pH 4.0; mass of activated carbon = 25 mg, and contact time = 70 min. At these optimized conditions, the maximum removal of nitrates is found to be 96.59%.
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
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
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.
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
Photocatalytic degradation of trimethoprim on doped Ti-pillared montmorillonite
(Elsevier, 2019) González, Beatriz; Trujillano, Raquel; Vicente, Miguel Ángel; Rives, Vicente; Korili, Sophia A.; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2
Montmorillonite pillared with titanium and doped with Cr3+ or Fe3+ has been tested for the photo-degradation of the antibiotic trimethoprim (trimethoxybenzyl-2,4-pyrimidinediamine) under different conditions, namely, in the dark or in UV light, with or without catalyst, finding excellent catalytic performance under photocatalytic conditions. The degradation by-products were preliminary analysed by mass spectrometry. The results suggested that the molecule broke in two halves, corresponding to its two existing rings. The process continued with the breakage of new fragments from the trimethoxybenzene half, these fragments later reacted with the methoxy groups in this part of the molecule, giving species with m/z values higher than that for the starting molecule, and with the breakage of new fragments.