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
Adsorption recovery of Ag(I) and Au(III) from an electronics industry wastewater on a clay mineral composite
(University of Science and Technology Beijing, 2019) Rakhila, Youness; Elmchaouri, Abdellah; Mestari, Allal; Korili, Sophia A.; Abouri, Meriem; Gil Bravo, Antonio; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The aim of this work is to investigate the ability of an adsorbent of a clay mineral composite to remove and recover gold and silver ions from wastewater. The composite was prepared by mixing phosphogypsum (PG), obtained from an industrial waste, and a natural clay mineral. The materials were characterized before and after use in adsorption by several techniques. Batch adsorption experiments were carried out, and the effects of the contact time and the pH and temperature of solution on the removal processes were investigated. The optimum pH for the adsorption was found to be 4. The adsorption of these metal ions reached equilibrium after 2 h of contact. The pseudo-first- and the pseudo-second-order kinetic models, as well as the Freundlich and the Langmuir isotherm equations, were considered to describe the adsorption results. The maximum adsorbed amount of 85 mg·g−1 Ag(I) and 108.3 mg·g−1 Au(III) was found. The recovery of the adsorbed gold and silver ions from the adsorbent was also analyzed. Strong acids appeared to be the best desorption agents to recover gold and silver ions. The use of aqua regia gave regeneration rates close to 95.3% and 94.3% for Ag(I) and Au(III), respectively. Finally, the removal of gold and silver ions from an industrial wastewater was tested in batch experiments, and percentage recoveries of 76.5% and 79.9% for Ag(I) and Au(III), respectively, were obtained. To carry out the industrial application of the proposed methodology, an economic viability study is required.
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
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
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
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
Use of response surface methodology to optimize triclosan adsorption on alumina pillared clays in a fixed-bed column for applications in solid-phase extraction
(Elsevier, 2023-04-01) Cardona Rodríguez, Yaneth; Korili, Sophia A.; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Fixed-bed column studies are generally conducted to consider possible applications in water-purification processes. In this work, three synthetic alumina pillared interlayered clays (Al-PILC) were analyzed in fixed-bed column studies for use as sorbents for solid-phase extraction (SPE) for the first time. Adsorption processes were studied for triclosan (TCS), which is an emerging pollutant (EP) that has been shown to have several health effects. Breakthrough curves were investigated by varying process parameters such as bed height (0.25–0.75 cm), inlet TCS concentration (20–60 mg/cm3 ), and flow rate (0.5–3 cm3 /min). Bohart-Adams, Bed Depth Service Time (BDST), and Thomas models were satisfactory applied to the results obtained for fixed-bed columns. The adsorption of TCS was successfully optimized for use in SPE for the three adsorbents studied using response surface methodology with a Box–Behnken design (RSM-BBD). The models developed were adequate for the experimental data (95% significance level), with high regression parameters (98.9–99.1). The optimum values for TCS adsorption on the fixed-bed column were 378.04, 367.78, and 378.93 mg (amount of adsorbent packed into the column), 0.5 cm3 /min (flow rate), 4.24, 3.96, and 3.85 (pH), and 2.56, 1.93, and 1.13 mg/dm3 (inlet TCS concentration) for Al-PILCAE, Al-PILCBE, and Al-PILCCM, respectively. From these results synthetic Al-PILC are effective and promising sorbents that can be used for analytical purposes in SPE, and that RSM-BDD is an effective and reliable tool for evaluating and optimizing the adsorption conditions for emerging contaminants in a fixed-bed column system.
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.