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
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
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
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+.
Embargo
Hydrocalumite and hydrocalumite-type compounds: a special type of layered double hydroxides
(Elsevier, 2025-04-01) Jiménez, Alejandro; Trujillano, Raquel; Gil Bravo, Antonio; Rives, Vicente; Vicente, Miguel Ángel; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
An exhaustive bibliographical review of one of the most peculiar Layered Double Hydroxides, LDH, namely hydrocalumite and hydrocalumite-type compounds, has been carried out. The main differences that make hydrocalumite a special and interesting LDH are described, as well as the main methods of synthesis. A comprehensive comparison is also made with respect to MgAl/carbonate hydrotalcite with a Mg/Al molar ratio of 2. Thermal behavior of hydrocalumite is also different than that of other LDH, leading to the formation of attractive Mixed Metallic Oxides, MMO. Thus, the applications of hydrocalumite, hydrocalumite-type compounds and the derived MMO in environmental remediation and heterogeneous catalysis and photocatalysis are presented. Hydrocalumite, contrary to hydrotalcite, is not currently commercialized on an industrial scale, probably because its preparation is more complicated. Considering the excellent properties of hydrocalumite and the price, abundance and biocompatibility of its components, the scaling of its production should be a key challenge to take advantage in its industrial application.
Open Access
White and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites as catalysts for toluene photodegradation from aqueous solutions
(MDPI, 2019) Mora, Lucas D.; Trujillano, Raquel; Rives, Vicente; Pérez Bernal, María Elena; Korili, Sophia A.; Gil Bravo, Antonio; Faria, Emerson H. de; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
The presence of volatile organic compounds in groundwater is a major concern when it is used as a drinking water source because many of these compounds can adversely affect human health. This work reports on the preparation and characterization of white and red Brazilian Sao Simao's kaolinite-TiO2 nanocomposites and their use as catalysts in the photochemical degradation of toluene, a significant volatile organic compound. The nanocomposites were prepared by a sol-gel procedure, using titanium bis(triethanolaminate)diisopropoxide as a precursor. Thermal treatments of the nanocomposites led to different polymorphic titania phases, while the clay changed from kaolinite to metakaolinite. This structural evolution strongly affected the photocatalytic degradation behavior-all the solids efficiently degraded toluene and the solid calcined at 400 degrees C, formed by kaolinite and anatase, showed the best behavior (90% degradation). On extending the photochemical treatment up to 48 h, high mineralization levels were reached. The advantage of photodegradation using the nanocomposites was confirmed by comparing the results from isolated components (titanium dioxide and kaolinite) to observe that the nanocomposites displayed fundamental importance to the photodegradation pathways of toluene.
Open Access
Preparation of Al/Fe-PILC clay catalysts from concentrated precursors: enhanced hydrolysis of pillaring metals and intercalation
(Royal Society of Chemistry, 2020) Vallejo, Carlos Andrés; Galeano, Luis Alejandro; Trujillano, Raquel; Vicente, Miguel Ángel; Gil Bravo, Antonio; Institute for Advanced Materials and Mathematics - INAMAT2
The modification of bentonite with Al-Fe species from different concentrated precursors at both stages: (i) the preparation of the (Al/Fe)-mixed pillaring solution and (ii) intercalation itself, was studied at lab scale. The final solids were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Cationic Exchange Capacity (CEC), textural analyses by nitrogen adsorption-desorption at 77 K, and hydrogen-temperature programmed reduction (H2-TPR). Finally, the modified clays were assessed as active materials in the Catalytic Wet Peroxide Oxidation (CWPO) of phenol under very mild conditions through 1.0 h of reaction: T = 25.0 °C ± 0.1 °C, pH = 3.7, ambient pressure (76 kPa), and 0.5 g catalyst per dm3. Metal hydrolysis by the dissolution of elemental aluminium (final Total Metal Concentration TMC = 4.62 mol dm-3) achieved the best results, decreasing the volume of solution per mass unit of clay required to successfully expand the layered starting mineral by a factor of close to 75, in comparison with the widespread conventional preparation using highly diluted Al-based pillaring solutions. Even in the absence of any solvent for the clay dispersion, the intercalating/pillaring method was shown to be favourable, as a novel strategy promoting the process intensification and subsequent preparation of Al/Fe- and other Al-based pillared clays at larger scales. The best catalyst prepared from concentrated precursors exhibited 79.1% phenol conversion, 19.3% TOC mineralization, and pretty low iron leaching (0.037 mg Fe dm-3; ∼0.12% w/w) in such a short catalytic assessment; all these results were quite comparable or even exceeded those exhibited by the catalyst prepared from dilute precursors. © 2020 The Royal Society of Chemistry.
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
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.
Open Access
Preparation of Ca2Al1–mFem(OH)6Cl 2H2O-doped hydrocalumites and application of their derived mixed oxides in the photodegradation of ibuprofen
(MDPI, 2022) Jiménez, Alejandro; Valverde, Marta; Misol, Alexander; Trujillano, Raquel; Gil Bravo, Antonio; Vicente, Miguel Ángel; Institute for Advanced Materials and Mathematics - INAMAT2
Aluminum from saline slags generated during the recycling of this metal, extracted under reflux conditions with aqueous NaOH, was used in the synthesis of hydrocalumite-type solids with the formula Ca2Al1–mFem(OH)6Cl 2H2O. The characterization of the obtained solids was carried out by powder X-ray diffraction, infrared spectroscopy, thermal analysis, element chemical analysis, N2 adsorption-desorption at -196ºC and electron microscopy. The results showed the formation of Layered Double Hydroxide-type compounds whose characteristics varied as the amount of incorporated Fe3+ increased. These solids were calcined at 400ºC and evaluated for the catalytic photodegradation of ibuprofen, showing promising results in the elimination of this drug by advanced oxidation processes. The CaAl photocatalyst (without Fe) showed the best performance under UV light for the photodegradation of ibuprofen.