Open Access
Synthesis of Cu-Al layered double hydroxides from aluminum saline slags
(Elsevier, 2023) Boulahbal, Aziza Imene; Santamaría Arana, Leticia; Azizi, A.; Boutahala, Mokhtar; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The use of saline slag, a hazardous waste generated during the recycling of aluminum, as aluminum source for the synthesis CuAl layered double hydroxides (LDH) is for the first time reported in this study. Due to the JahnTeller effect, divalent copper–aluminum LDH come usually with impurities and a pure CuAl LDH is not easy to obtain. The effect of synthesis pH has been examined by comparing LDH synthesized at various pH, ranging from 6 to 12 via a co-precipitation method using aluminum obtained from an alkaline extraction of the slag. For comparison purposes, a sample was synthesized at pH = 9 using commercial aluminum Al(NO3)3⋅9H2O instead of extracted aluminum. The effects of the aging time and calcination temperature are also discussed. The LDH and their calcined metal mixed oxide (layered double oxide, LDO) have been analyzed with several characterization techniques: powder X-ray diffraction (PXRD), N2 adsorption at − 196 ◦C, thermogravimetric analysis (TGA), temperature programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy and energy-dispersive X-ray spectroscopy (TEM and EDS). Synthesis pH has been proved not only to have a significant effect on the nature of secondary phases but also on the structure and morphology of the samples.
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
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
Multifunctional heterogeneous catalysts: Tetrakis (pentafluorophenyl)porphinato]iron(III) immobilized on amine-functionalized Diatomaceous Earth for catalytic and adsorption applications
(Elsevier, 2023) Do Prado, Marcus Vinicius; González, Beatriz; Vicente, Miguel Ángel; Trujillano, Raquel; Nassar, Eduardo José; Gil Bravo, Antonio; Santamaría Arana, Leticia; Korili, Sophia A.; Marçal, Liziane; Faria, Emerson H. de; Ciuffi, Katia J.; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The use of Diatomaceous Earth (DE) as a promising support of a synthetic metalloporphyrin is reported, trying to heterogenize metalloporphyrin catalysts to mimicking enzyme site isolation and improving reaction selectivity. New multifunctional hybrid materials consisting of DE amino–functionalized with aminopropyltriethoxysilane (DE–APTES), followed by grafting with [meso–tetrakis(pentafluorophenyl)porphinato]iron(III) (DE–APTES–FeTFPP), were prepared and fully characterized. FeTFPP was grafted into DE–APTES via the amine groups (band at 1570 cm–1 ). The brown color of the materials indicated that FeTFPP was immobilized in the matrix; a Soret band characteristic of ironporphyrin located in a confined space, was found at 416 nm. Leaching studies confirmed that the ironporphyrin was entrapped and not just adsorbed on the silica surface. DE was composed of typical quartz and cristobalite crystalline phases and amorphous silica. The intensity of its characteristic reflection at 22◦ (2θ) decreased in the presence of FeTFPP, evidencing that the ironporphyrin influenced the organization of the material. Catalytic tests using DE–APTES–FeTFPP in cyclooctene epoxidation to cyclooctene oxide (56 % yield, with complete selectivity for the epoxide) and cyclohexane oxidation (4 % yield of oxidized products, with ketone/alcohol selectivity ~ 3:1), evidenced the versatility of the catalyst and the multifunctionality of the resulting hybrid materials and the ability of DE as a promising natural support for ironporphyrin catalysts. Finally, the capacity of the materials as CO2 adsorbents was evaluated in the temperature range 100–200 ◦C. DE–APTES showed a maximum adsorption capacity of 1.26 mmol/g at 100 ◦C, 18 times higher than the value found under the same conditions for the non–functionalized support.
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
Effect of gold nanoparticles on SiO2@g-C3N4 catalyst for the degradation of amoxicillin
(Elsevier, 2024-08-05) Santamaría Arana, Leticia; Korili, Sophia A.; Gil Bravo, Antonio; López de Luzuriaga Fernández, José Manuel; Monge Oroz, Miguel; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Gold nanoparticles in different proportions (0.5 and 1 %) have been grafted at the surface of a SiO2@g-C3N4 nanotube-based composite (SiO2 nanotubes obtained from halloysite clay) and also g-C3N4 (for comparison purposes) to test their degradation capacity over the antibiotic amoxicillin proving that the introduction of these nanoparticles on the catalyst modifies the degradation mechanism followed by the pollutant. Results obtained show that the introduction of the appropriate percentage of gold NPs in the composite improves amoxicillin degradation efficiency and establish a direct correlation between the presence of gold NPs and the production of ∙O2.
Open Access
Multifunctional nanocomposites based on kaolinite/titania/iron applied to hydrogen peroxide production and bisphenol-A removal
(Elsevier, 2024-11-06) Do Prado, Marcus Vinicius; Lima, Vinicius; Oliveira, Larissa; Nassar, Eduardo José; Marçal, Liziane; Faria, Emerson H. de; Vicente, Miguel Ángel; Trujillano, Raquel; Santamaría Arana, Leticia; Gil Bravo, Antonio; Korili, Sophia A.; Ciuffi, Katia J.; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The rising global demand for hydrogen peroxide, recognized for its eco-friendly properties, underscores the need for greener synthesis methods. Traditional production processes pose environmental risks, while direct synthesis faces challenges like water formation, explosion hazards, and stability issues, limiting industrial application. On the other hand, Bisphenol A (BPA), an endocrine disruptor widely used in plastics, presents significant environmental and health concerns due to its potential leaching into food and water. The present work introduces efficient and selective photocatalysts aimed at sustainable hydrogen peroxide synthesis and BPA degradation. Both processes were enhanced by the synergistic properties of Fe2O3–TiO2 nanoparticles dispersed within a kaolinite matrix. The Fe2O3-TiO2 photocatalysts, characterized by photoluminescence spectroscopy and X-ray diffraction, showed reduced emission upon iron incorporation and anatase presence on the kaolinite surface. The photocatalytic activity was evaluated through hydroxylation of terephthalic acid, revealing a 127 umol/L min hydroxylation rate for the KaFeTi400 sample. BPA degradation studies indicated optimal performance in acidic conditions, achieving 96 % removal in 2 h and 98 % in 4 h, with the addition of H2O2 enhancing efficiency. Further, the photocatalyst facilitated benzyl alcohol oxidation to benzaldehyde, demonstrating a H2O2 production rate of 120 umol. These findings highlight the multifunctional capabilities and environmental benefits of the photocatalyst, underscoring its potential for sustainable hydrogen peroxide synthesis and broader applications in environmental remediation. The catalysts address the pressing challenges associated with hydrogen peroxide synthesis and pollutant removal, particularly in the context of sustainability and environmental impact.
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
Synthesis of high-surface-area C3N4 deposited on halloysite-derived silica nanotubes: enhanced visible light degradation of norfloxacin
(Elsevier, 2024) Santamaría Arana, Leticia; Korili, Sophia A.; Gil Bravo, Antonio; López de Luzuriaga Fernández, José Manuel; Monge Oroz, Miguel; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
Silica nanotubes, obtained from halloysite clay nanotubes that were calcined and acid-activated, were used as support for graphitic carbon nitride (g-C3N4) via a simple deposition method. They were chosen in order to avoid any agglomeration issues, as there was an increase of the specific surface area with respect to pristine halloysite. The composite was tested for the degradation of a persistent emerging pollutant in water, namely, antibiotic norfloxacin. Experiments were performed in darkness (until adsorption-desorption equilibrium was attained) and, subsequently under visible light. Comparison of the performance between the photocatalysts shows that the composite was 49% faster than g-C3N4. The introduction of persulfate in the lumen of the nanotubes via vacuum negative-pressure suction and injection was also tested for the generation of .OH radicals that fasten the degradation rate, obtaining a further 47% increase in the degradation rate of norfloxacin thanks to the release of this anion during the photodegradation process. The degradation mechanism of SiO2/g-C3N4 sample was studied with trapping experiments by the use of scavengers that were introduced to quench the photodegradation: triethanolamine for photoexcited holes (h+), tert-butanol for hydroxyl radicals (.OH) and a N2 atmosphere for superoxide radicals (.O2.).
Open Access
Zn-Ti-Al layered double hydroxides synthesized from aluminum saline slag wastes as efficient drug adsorbents
(Elsevier, 2020) Santamaría Arana, Leticia; López Aizpún, María; García Padial, Marcos; Vicente, Miguel Ángel; Korili, Sophia A.; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Gobierno de Navarra / Nafarroako Gobernua, PI017-PI039 CORRAL; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
This work reports the synthesis of Zinc-Titanium-Aluminum (ZnTiAl) layered double hydroxides (LDH) with various proportions of Al[sbnd]Ti and a Zn/(Al[sbnd]Ti) molar ratio of 3:1 by the co-precipitation method. Two series, made with commercial aluminum (Al) and aluminum extracted from saline slags (Al*), have been considered. Structural characterization and comparison of the two series has been made using powder X-ray diffraction (PXRD), Nitrogen physisorption at 77 K, Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Thermogravimetry measurements. The adsorption capacity of diclofenac and salicylic acid, as examples of emergent pollutants, by the different LDH on batch and fixed-bed column experiments has been analyzed. The effect of various parameters, such as the pH, the initial concentration of pollutant, the mass of adsorbent and the contact time, on the sorption behavior were studied and compared. The contact time to attain equilibrium for maximum adsorption was found to be between 100 and 400 min. The kinetic and equilibrium results were correlated to several adsorption and isotherm equation models. The synthesized materials were more effective in removing diclofenac than salicylic acid, being Zn6Al*2 the hydrotalcite that showed the highest adsorption capacity. The results showed a new application of a material obtained from the valorization of an industrial waste such as aluminum saline slags.