Open Access
Progress and perspectives on pillared clays applied in energetic and environmental remediation processes
(Elsevier, 2020) Gil Bravo, Antonio; Vicente, Miguel Ángel; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
Pillared interlayered clays (PILCs) are materials that show a two-dimensional layered porous structure with properties that could be interesting alternatives to zeolites and other microporous solids. Some of the properties that make these materials interesting are specific surface area, high exchange capacity, low permeability, swelling ability, relatively good heat resistance stability, high acidic properties, and relatively low price. PILCs have attracted intense research among several years in relation to the possible control of these properties and environmental applications. The current short work is devoted to the tendencies and new insights in to the last five years of PILCs as adsorbents and heterogeneous catalysts. The work finishes considering the future application prospects.
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
Hydrocalumite-TiO2 hybrid systems synthesized from aluminum salt cake for photodegradation of ibuprofen
(Elsevier, 2024) Rebollo, Beatriz; Jiménez, Alejandro; Trujillano, Raquel; Rives, Vicente; Gil Bravo, Antonio; Vicente, Miguel Ángel; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Synthesis of hydrocalumite–TiO2 hybrid systems and their use in photodegradation of ibuprofen is reported for the first time. Hydrocalumite was prepared with Al3+ recovered from an aluminum slag (circular economy), TiO2 was deposited on hydrocalumite by hydrolysis of titanium(IV) isopropoxide, and the solids thus obtained were calcined at 400 and 750 ºC. The solid calcined at 400 ºC was essentially amorphous, showing the presence of calcite due to the fixation of atmospheric CO2, while the solid calcined at 750 ºC was composed of mayenite, perovskite and rutile. The calcined solids were used for catalytic degradation of ibuprofen (50 ppm in aqueous solutions) under UV irradiation, obtaining better results than when using commercial TiO2–P25 from Degussa. Under the specific conditions used, the degradation took place in the initial steps of the process, mainly giving rise to species with higher molecular mass than initial ibuprofen.
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.
Open Access
Microwave-assisted pillaring of a montmorillonite with al-polycations in concentrated media
(MDPI, 2017) González, Beatriz; Pérez, Alba Helena; Trujillano, Raquel; Gil Bravo, Antonio; Vicente, Miguel Ángel; Química Aplicada; Kimika Aplikatua
A montmorillonite has been intercalated with Al3+ polycations, using concentrated solutions and clay mineral dispersions. The reaction has been assisted by microwave radiation, yielding new intercalated solids and leading to Al-pillared solids after their calcination at 500 °C. The solids were characterized by elemental chemical analysis, X-ray diffraction, FTIR spectroscopy, thermal analyses, and nitrogen adsorption. The evolution of the properties of the materials was discussed as a function of the preparation conditions. Microwave treatment for 2.5 min provided correctly pillared solids.
Open Access
Optimization of hydrocalumite preparation under microwave irradiation for recovering aluminium from a saline slag
(Elsevier, 2021) Jiménez, Alejandro; Misol, Alexander; Morato, Álvaro; Rives, Vicente; Vicente, Miguel Ángel; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2
Aluminium was successfully extracted by treating an aluminium slag with aqueous NaOH under reflux conditions. This solution was purified by precipitation of silicon species by addition of HCl up to pH = 1, and used for preparing hydrocalumite (Ca2Al(OH)6Cl·2H2O) by the coprecipitation method. The effect of temperature on the properties of hydrocalumite prepared under microwave (MW) irradiation was studied. Characterization of the obtained solid was carried out by powder X-ray diffraction (PXRD), thermal analysis, FT–IR spectroscopy, chemical analysis, electron microscopy and N2 adsorption–desorption at −196 °C. The results showed that the use of the extracted aluminium solution allowed to obtain hydrocalumite by the coprecipitation method and that the temperature of the MW ageing treatment had a large effect on the formation of side phases, in addition to hydrocalumite. The results here reported demonstrate that formation of hydrocalumite is an effective method for the recovering of aluminium from its waste.
Open Access
M(II)-Al-Fe layered double hydroxides synthesized from aluminum saline slag wastes and catalytic performance on cyclooctene oxidation
(Elsevier, 2022) Santamaría Arana, Leticia; Oliveira-Garcia, L.; Faria, Emerson H. de; Ciuffi, Katia J.; Vicente, Miguel Ángel; Korili, Sophia A.; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Aluminum was extracted from saline slags via an alkaline method and employed in the synthesis of Layered Double Hydroxides (LDH) with various M2+ cations (Co, Mg, Ni and Zn), while Al and Fe were the M3+ cations, using the co-precipitation method and a M2+/M3+ 2:1 ratio. The structural characterization of the samples was performed with powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), nitrogen physisorption at 77 K, thermogravimetric analysis (TGA), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). Their catalytic performance was tested for the oxidation of olefins (cyclooctene) and their biomimetic potential was analyzed. Results show a great selectivity towards epoxides with no other products obtained. Reaction yields followed the descending order Co4AlFe, Zn4AlFe, Ni4AlFe, and Mg4AlFe, the sample with cobalt as M2+ converting up to 85% of cyclooctene.
Open Access
Progress in the removal of pharmaceutical compounds from aqueous solution using layered double hydroxides as adsorbents: a review
(Elsevier, 2020) Santamaría Aquilué, Rafael; 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
Emerging contaminants and, among them, pharmaceutical compounds, have a significant impact on water ecosystems. Layered Double Hydroxides (LDH), being easy to synthesize and cheap materials, have recently gained attention as adsorbents in aqueous solutions. This work describes the latest research performed in the adsorption capacity of LDH towards both antibiotics and Non-Steroidal Anti-Inflammatory Drugs (NSAID) describing and analyzing the synthesis conditions (Me2+:Me3+ molar ratio, calcination temperature, choice of metals for the memory effect), kinetics and isotherm models used, use of support (more practical in a 3D over a 2D form), temperature effect and several techniques for the recovery of the adsorbents. LDH exhibited great performance and potential as clean adsorbents for these emerging contaminants.
Open Access
Removal of heavy metals from aqueous solutions by adsorption on zeolites synthesized from aluminum saline slags
(Elsevier, 2024-10-31) Jiménez, Alejandro; Trujillano, Raquel; Rives, Vicente; Vicente, Miguel Ángel; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Three heavy metals (Cu2+, Cd2+ and Pb2+) were removed from aqueous solutions using zeolites prepared from saline slags, a very important waste generated during aluminum recycling. Zeolites were characterized by powder X-ray diffraction, thermal analysis, Fourier transform infrared spectroscopy, X-ray microfluorescence, element chemical analysis, nitrogen adsorption at -196 °C and electron microscopy. The textural and structural properties of X-type faujasite zeolite convert it in a promising adsorbent in aqueous streams. Removal of the heavy metals was evaluated in batch mode, studying the adsorbent dose, the initial concentration of the heavy metal, the selectivity of the solid in case of mixtures with various metal cations and the recyclability of the solid. The kinetic and equilibrium results were evaluated using both pseudo-first- and pseudo-second-order kinetics, and Langmuir, Freundlich and Toth equation isotherms for the equilibrium. The time needed to reach equilibrium was between 10 and 20 min. Faujasite was highly effective in removing Cu2+, Cd2+ and Pb2+ from aqueous solutions, much higher than analcime and pollucite, other two zeolites recently synthesized by us from aluminum slags, and used in this work for comparison purposes. The maximum adsorption capacity was 591 mg/g for Pb2+, 304 mg/g for Cu2+ and 279 mg/g for Cd2+.
Open Access
Synthesis of MOF@aluminum saline slag-based composites for CO2 capture at moderate temperatures
(Elsevier, 2025-09-01) Muñoz Alvear, Helir Joseph; 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; Gobierno de Navarra / Nafarroako Gobernua
Combining metal–organic framework (MOF) materials and aluminum-containing saline slag residues opens a promising research avenue. This approach reduces the environmental impact of aluminum production by integrating industrial waste in the development of advanced materials that adhere to circular economy principles. It also addresses some inherent stability issues observed in pure MOFs. This study is the first to propose the use of this industrial by-product as a cost-effective and environmentally friendly modulator for controlling the phase transition between MIL-96(Al) and MIL-110(Al). For the first time, novel MOFs composites (MOF@RW1*-n; n = 25, 50, 75% waste) and saline slag waste (RW1*)—a by-product of initial aluminum extraction in an acidic medium—were synthesized in situ by preparing the MOF on RW1* via hydrothermal treatment and subsequently tested as CO2 adsorbents at up to 225 ◦C and 80 kPa. The optimized RW1* content in the composite proved critical in determining the formation of specific crystalline structures (MIL-96(Al) or MIL-110(Al)), ultimately yielding hybrid materials with enhanced textural properties and thermal stability.