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
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
Enhancing adsorptive performance of Cu-Al layered double hydroxides from aluminum saline slags: Insights from response surface methodology and molecular dynamic simulation
(Elsevier, 2024-12-01) Boulahbal, Aziza Imene; Santamaría Arana, Leticia; Bourzami, Riahd; Bendrihem, Aymene Salah; Boutahala, Mokhtar; Korili, Sophia A.; Gil Bravo, Antonio; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
This study aims to optimize the adsorption process of gallic acid (GA) on Cu-Al layered double hydroxides (LDHs) synthesized via a co-precipitation method at various pH levels. The procedure is based on the adsorption of organic pollutants from aqueous solutions, with evaluations carried out based on operational parameters such as pH, initial concentration, and adsorbent quantity. Two series of LDHs were compared: one using aluminum extracted from saline slags and the other using a commercial aluminum salt as source of aluminum. Saline slags, a by-product of aluminum recycling, are particularly hazardous due to their high toxicity and potential for environmental contamination. Extracting aluminum from these slags and using it in the synthesis of LDHs not only helps in eliminating a dangerous waste but also creates materials with beneficial environmental applications. The adsorption process was optimized using response surface methodology (RSM) coupled with Box- Behnken design (BBD) to assess the effects of key operational parameters. Besides gallic acid, other organic pollutants such as diclofenac and salicylic acid were also evaluated for removal from aqueous solution. The LDH /LDO were characterized by X-ray diffraction (XRD), ATR infrared spectroscopy (ATR-IR), scanning and transmission electron microscopy (SEM/TEM), thermogravimetric analysis (TGA), and nitrogen adsorption at -196ºC. The merit data indicate that the material synthesized at pH = 9 with extracted aluminum exhibits superior adsorption capacity for gallic acid, demonstrating the highest removal rate, nearly reaching 100 %, and achieving equilibrium more quickly than other samples. This superior adsorption performance is also notable for salicylic acid and diclofenac. After four regeneration cycles, the adsorption rate of the adsorbent remains stable, indicating that CCA9 maintains a consistent and efficient adsorption performance. This highlights the robustness of the material and its high reusability in prolonged adsorption applications. Molecular dynamics simulations (MDS) revealed that the adsorption process occurs spontaneously, driven by weak interactions: van der Waals, intermolecular, hydrogen bonding, π-interactions and short contacts.

Korili, Sophia A.

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