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
A comparative study of the catalytic performance of nickel supported on a hibonite-type La-hexaaluminate synthesized from aluminum saline slags in the dry reforming of methane
(Elsevier, 2022) 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
In this work, a hibonite-type Ni/La-hexaaluminate (Ni/LHA) synthesized from an industrial waste is used and compared as catalyst in the dry reforming of methane (DRM) at 973 K. The structure, catalytic behavior, and stability during a run time of at least 50 h of three Nicatalysts obtained from two commercial supports and two preparation methods were used for comparison. An aluminum solution (9.40 g/L) obtained from an aluminum 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. The Ni/LHA catalyst (10 wt% NiO) was obtained by impregnation of the synthesized support, calcined previously at 1473 K for 2 h. The resulting solids were characterized by several techniques as: X-ray diffraction (XRD), N2 adsorption at 77 K, temperature-programmed reduction (TPR), scanning electron microscopy (SEM) and transmission electron microscopy (HR-TEM). In order to compare the catalytic behavior and properties of the Ni/LHA catalyst, three Ni catalysts obtained from two commercial supports (g-Al2O3 and SiO2) and two preparation methods (wet impregnation (I) and precipitation-deposition (PD)) were synthesized. 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 Ni/LHA and NieI/ SiO2. The NiO species observed, with crystallite sizes between 9.7 and 40.4 nm, confirm the X-ray structural analyses. The Ni/LHA catalyst was found to be active and very stable in the DRM reaction after 50 h. The catalytic behavior was evaluated from the CO2 and CH4 conversions, as well as the H2/CO selectivity, with values of 99% over almost all the time range evaluated. The behavior of this catalyst is comparable to that of NieI/Al2O3 and NiPD/SiO2. The results found indicating that the strong interaction of nickel with the support favors the stability of the catalysts in the DRM reaction.
Open Access
Synthesis strategies of alumina from aluminum saline slags
(Elsevier, 2023) Grande López, Lucía; Vicente, Miguel Ángel; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Aluminum saline slags is a waste of the metallurgical industry that presents serious environmental problems since it needs very extensive areas for its disposal, the toxicity it causes in the atmosphere and groundwater, in addition to high transportation costs. The valorization of this residue by the synthesis of alumina, a compound widely used in the chemical industry, generates a high impact and great interest. In this work, the strategies for synthesizing alumina from aluminum saline slags are reviewed in a context of growing demand for this metal and environmental crisis. The first sections present the aluminum production processes, both from natural bauxite (primary process) and from the recycling of materials with a high aluminum content (secondary process); paying attention to the waste generated and what environmental problems they produce. The main investigations that have allowed to address the recovery of the waste generated are described below, focusing on the processes of recovery/extraction of the aluminum present in its composition. The aluminum in these residues can be found as a metal or forming other compounds such as simple or mixed oxides. Chemical processes are the most relevant, especially those that deal with the acid and alkaline extraction of the metal. The most important section of the work reports on the methods of synthesis of Al2O3, highlighting the methods of precipitation, sol-gel, hydrothermal synthesis, and combustion, among others. The work ends with a summary and conclusions section.
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
Layered double hydroxides for CO2 adsorption at moderate temperatures: synthesis and amelioration strategies
(Elsevier, 2023) Santamaría Arana, Leticia; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Curving the CO2 atmospheric levels is one of the challenges of this century, given its direct impact on climate change. Of the several strategies of CO2 capture and storage, sorption-enhanced water–gas shift (SEWGS) process, a combination of CO2 adsorption and the water–gas shift reaction, has been appointed as one of the most promising techniques due to is low energy consumption and high efficiency. SEWGS operating settings at both moderate temperature (200–450 ◦C) and high pressure (more than 10 bar) bring the need to find an adsorbent capable of working at these conditions. Calcined layered double hydroxides (LDH) have been proven to give the best results in this range of pressure/temperatures even though its performance can be greatly improved. Herein, a state-of-art of the research accomplished up until now is presented. Several strategies can be followed to improve the adsorbents performance: the synthesis method, LDH composition, modifications employed to promote their adsorption capacity or how the adsorption conditions can affect their efficiency
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.
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
Metal-Al layered double hydroxides synthesized from aluminum slags as efficient CO2 adsorbents at pre- and post-combustion temperature
(Elsevier, 2023) Santamaría Arana, Leticia; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Layered double hydroxides (LDH) have been proposed as the materials that offer the best performance in the moderate-temperature range, between 200 and 450 °C, for CO2 adsorption, so the effect of some synthesis parameters and surface modification on their adsorption capacities is herein investigated. This work reports the use of M2+ (Co, Mg, Ni and Zn)/Al layered double hydroxides synthesized with a 3:1 molar ratio by the co-precipitation method and using aluminum extracted from saline slags as source of this metal as CO2 adsorbents. The synthesis and use of Zn/TiAl is also reported considering several proportions of Al-Ti. Structural characterization and comparison of the series has been achieved using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at single bond196 °C and thermogravimetry measurements (TGA). The performance of calcined LDH as CO2 adsorbents was evaluated in the 50 – 400 °C temperature range and 80 kPa and results show that Ni6Al2 and Mg6Al2 samples present a significant adsorption capacity at low temperature (0.382 and 0.292 mmolCO2/g, respectively). At 400 °C only Mg6Al2 maintains its high adsorption capacity (0.275 mmolCO2/g) compared to the other calcined LDH. Its adsorption capacity at moderate-temperature range was proven to be better than that of a commercial Mg6Al2 sample. In all materials the CO2 adsorption capacity at 200–450 °C increased by incorporating potassium (K2CO3 and KOH as sources) up to 0.58 mmolCO2/g for Mg6Al2 +K2CO3. The addition of the amine TEPA in the low-temperature range worked for Co6Al2 and Mg6Al2 (increment > 40 %). In the case of Zn6Al2, the partial substitution of Al by Ti also increased the CO2 adsorption capacity from 0.177 to 0.244 mmolCO2/g, finding isosteric heats between 17.07 and 23.30 kJ/mol using the Clausius-Clapeyron equation.
Open Access
Titania-triethanolamine-kaolinite nanocomposites as adsorbents and photocatalysts of herbicides
(Elsevier, 2021) Ferreira, Ana Vera de Toledo Piza Figueiredo; Barbosa, Lorrana Vietro; Souza, Suelen Delfino de; Ciuffi, Katia J.; Vicente, Miguel Ángel; Trujillano, Raquel; Korili, Sophia A.; Gil Bravo, Antonio; Faria, Emerson H. de; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Kaolinite-titania adsorbents/photocatalysts were prepared by functionalizing a kaolinite with titanium(IV) triethanolaminate isopropoxide by the sol–gel route. These materials were characterized by various techniques and applied in adsorption studies (kinetic and equilibrium) of the herbicides diuron, hexazinone, and tebuthiuron. Photodegradation studies were also conducted with the materials submitted to heat-treatment at 400, 700, or 1000 °C. The basal spacing increased from 0.71 to 1.08 nm when pure kaolinite was functionalized with titanium triethanolaminate units. The materials displayed FTIR bands of –CH, –NH2, and Ti–OH groups, thereby confirming that titanium alkoxide was present in the kaolinite interlayer space. The pseudo second-order model was the best for describing the kinetic adsorption process. In the equilibrium study, the Langmuir model best described the adsorption mechanism. The photodegradation studies showed that the kaolinite-titania nanocomposites heat-treated at 400 and 700 degraded diuron, hexazinone, and tebuthiuron efficiently due to the presence of metakaolin and formation of the anatase phase. © 2021 Elsevier B.V.