Raquel Trujillano

Universidad de Salamanca, Helmantica, Castille and León, Spain

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Publications (86)226.7 Total impact

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    ABSTRACT: Montmorillonite has been treatedwith Ti-based solutions, alone or dopedwith Cu2+, Fe3+ or Cr3+ cations, yielding new intercalated solids, which have been calcined at various temperatures to test the stability of the soformed pillars. The solids calcined at 500 °C were fully characterized by chemical analysis, X-ray diffraction, FT-IR spectroscopy, thermal analyses, nitrogen adsorption and acidity evaluation. The evolution of the specific surface area, porosity and acidic properties is discussed, analysing the effect of pillaring and doping procedures on these properties.
    No preview · Article · Dec 2015 · Applied Clay Science
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    ABSTRACT: The use of hydrotalcites for the synthesis of two chiral building blocks in a simple way is described as a new and green methodology. The synthesis of these compounds implies a regioselective Baeyer-Villiger reaction in a very selective way with ulterior opening and lactonisation. This methodology should be considered green for the use of hydrogen peroxide as the only oxidant and hydrotalcites as the catalyst, and because no residues are produced apart from water. The procedure is very adequate for using in gram scale, in order to increase the value of the obtained compounds. The conditions are excellent and can be applied for nonstable compounds, as they are very mild. The synthesised compounds are magnific starting materials for the synthesis of biologically active or natural compounds. The use of a cheap, commercial and chiral compound as carvone disposable in both enantiomeric forms adds an extra value to this methodology.
    Full-text · Article · Oct 2015 · Natural product research
  • R. Trujillano · E. Rico · M.A. Vicente · V. Rives · I. Sobrados · J. Sanz
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    ABSTRACT: The synthesis using microwave radiation of saponites containing Co2+, Zn2+ or Cu2+ in octahedral positions has been explored (in the case of Cu2+, together with Mg2+ or Ni2+). Pure saponite phases were formed under some synthesis conditions, although in other cases some impurities were also formed. Microwave treatment at 180°C favored the formation of ordered solids, but induced the crystallization of other phases in some cases. Cu2+-containing saponites were formed only if Mg2+ or Ni2+ were used as octahedral sheet co-cations. The solids were characterized by different techniques, including MAS-NMR spectroscopy, which gave very precise information in the case of Zn-saponite, allowing us to estimate the content of tetrahedral Al, but much more undefined information for samples with paramagnetic cations. Nevertheless, the presence of tetrahedral Fe3+ and octahedral Fe2+ species was evidenced. Cu2+ slightly perturbed the NMR signals, while Co2+ strongly perturbed 27Al, 23Na and especially 29Si NMR spectral signals.
    No preview · Article · Oct 2015 · Applied Clay Science
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    Full-text · Dataset · Sep 2015

  • No preview · Article · Sep 2015 · Applied Clay Science
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    ABSTRACT: A set of TiO2-modified montmorillonite meso-microporous materials, as photocatalysts, was successfully prepared in different ways and evaluated by the photodegradation of 4-nitrophenol (4-NP) in water, since it is a recalcitrant organic pollutant. The effects of photocatalysts' preparation methods on their textural, structural and catalytic properties were tested. To understand the relationship between the photocatalysts structure and performance, these were characterized by X-Ray Diffraction (XRD), UV-spectroscopy, Scanning Electron Microscopy/Energy Dispersive X-ray spectroscopy (SEM/EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray fluorescence (XRF), specific surface area and porosity measurements. A high specific surface area (up to 231 m 2 /g), a meso-microporous structure and a high stability have been found for the TiCl4-M and TiCl3-M prepared photocatalysts. In addition, to improve the 4-NP degradation, various parameters' effect was studied such as the type of the photocatalyst, its amount loading, the pH of the 4-NP solution and the initial 4-NP concentration. Then, the 4-NP degradation rate has reached 99% only when Anatase Titanium dioxide was supported on montmorillonite, at pH=5, with 0.2 g/100 mL of photocatalyst (TiCl4-M or TiCl3-M) amount and a 4-NP concentration equal to 20 mg.L-1 .
    Full-text · Article · Sep 2015
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    Full-text · Dataset · Sep 2015
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    ABSTRACT: A purified natural kaolinite was functionalized with titanium(IV) isopropoxide via the hydrolytic sol-gel route and thermally treated at several temperatures, between 100 and 1000 °C, for 24 h. The resulting solids were used for photodegradation (λ=365 nm, 30 W) of Methylene Blue (MB) and Methyl Orange II (MOII) dyes. All the solids efficiently degraded the dyes and almost total bleaching of the aqueous solutions was observed after 1 h. The best results were found for the solid heated at 400 °C, which degraded 93% of MOII and 99% of MB. Comparative studies with titanium oxide P25 from Degussa were tested and the results reveal lower yields than our systems (45% MB and 15% MOII, 1 h). Kaolinite could promote the dispersion of TiO2 on the clay surface allowing a fast degradation of dyes. This effect was confirmed by comparison of the results from isolated components (titanium oxide and kaolinite) and titanium oxide-kaolinite nanocomposites.
    Full-text · Article · May 2015 · Catalysis Today
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    ABSTRACT: Nanosized copper ferrite-type materials (CuxFe3–xO4, 0 ≤ x ≤ 1) have been prepared by combination of co-precipitation and mechanochemical activation and/or thermal treatment. The crystalline structure and morphology of the obtained ferrite nanopowders have been characterized by different instrumental methods, such as Powder X-ray diffraction (PXRD), Mössbauer and FT-IR spectroscopies, specific surface area and porosity measurements, thermal analyses (Differential Thermal Analysis and Thermogravimetric Analysis) and Temperature-Programmed Reduction. The average crystallite size of copper ferrites ranged between 7.8 and 14.7 nm and show a superparamagnetic and collective magnetic excitations nature. The photocatalytic decolorization of Malachite green oxalate under different UV illumination intervals was examined using these copper ferrites as photocatalysts. The results indicate that the prepared nanostructured copper ferrites showed enhanced photocatalytic activity and amount adsorbed Malachite Green dye. The co-precipitated nanosized copper ferrite powder with a low content of copper metal ions in a magnetite host structure (Cu0.25Fe2.75O4) showed an apparent pseudo-first-order rate constant 15.4 × 10−3 min−1 and an amount adsorbed Malachite Green as model organic dye pollutant per 1 g catalyst of 33.4 ppm/g after the dark period. The results confirm that the copper ferrites can be suitable for photocatalytic treatment of wastewaters containing organic dyes. The new aspect of presented investigations is to study the influence of different degree of incorporation of copper ions into the magnetite host structure and preparation methods on the photocatalytic properties of nanosized copper ferrite materials and obtaining of potential photocatalyst (Cu0.25Fe2.75O4) with higher photocatalytic activity (15.4 × 10−3 min−1) than that of the standard referent Degussa P25 (12 × 10−3 min−1) for degradation of organic dye Malachite green under UV irradiation.
    No preview · Article · May 2015 · Materials Chemistry and Physics
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    ABSTRACT: This study aimed to assess the capacity of saponite modified with n-hexadecyltrimethylammonium bromide (CTAB) and/or 3-aminopropyltriethoxysilane (APTS) to adsorb and remove caffeine from aqueous solutions. Powder X-ray diffraction (PXRD) revealed increased basal spacing in the modified saponites. Small-angle X-ray scattering (SAXS) confirmed the PXRD results; it also showed how the different clay layers were stacked and provided information on the swelling of natural saponite and of the saponites functionalized with CTAB and/or APTS. Thermal analyses, infrared spectroscopy, scanning electron microscopy, element chemical analysis, and textural analyses confirmed functionalization of the natural saponite. The maximum adsorption capacity at equilibrium was 80.54 mg/g, indicating that the saponite modified with 3-aminopropyltriethoxysilane constitutes an efficient and suitable caffeine adsorbent.
    Full-text · Article · May 2015 · ACS Applied Materials & Interfaces
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    ABSTRACT: Rare earth (RE = Eu, Y and Tb) and zinc layered hydroxide salts intercalated with nitrate anions were synthesized, followed by exchange with 2-aminobenzoate. The obtained compounds were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and ultraviolet visible (UV–vis) spectroscopies, fluorescence measurements and thermal analysis (TGA/DTA). The results from FTIR spectroscopy suggest a direct coordination of 2-aminobenzoate to the metal cations of the inorganic layered structure. The organic derivative products from the intercalation reactions absorb a broader range of UV-light in relation to that shown by the parent material; the photoluminescence measurements present a strong violet, blue and green luminescence under UV-light excitation for layered compounds with, Zn, Y and Tb, respectively. Rare earth hydroxide salts (RE-LHS) are potential alternative matrices for the immobilization of organic species to produce luminescent materials
    Full-text · Article · Apr 2015 · Materials Research Bulletin
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    ABSTRACT: An Algerian montmorillonite was modified with two organic surfactants, methyltriphenyl phosphonium bromide and n-hexyltriphenyl phosphonium bromide. The solids obtained were used as adsorbents to remove Orange II, an anionic dye from aqueous solutions. Batch experiments were conducted to study the effects of temperature (20–60°C), initial concentration of adsorbate (50–150 mg L−1) and pH of solution 6.5 on dye adsorption. Due to their organophilic nature, exchanged montmorillonites were able to adsorb Orange II at a very high level. Adsorption of Orange II for B-NHTPB and B-MTPB at different pH show that the adsorption capacity clearly decreases with an increase in pH of the initial solution from 2 to 8, this decrease being dramatic for pH > 8. This may be due to hydrophobic interactions of the organic dye with both phosphonium molecules and the remaining non-covered portion of siloxane surface. The kinetics of the adsorption was discussed on the basis of three kinetic models, i.e., the pseudo-first-order, the pseudo-second-order, and the intraparticle diffusion models. Equilibrium is reached after 30 min and 60 min for B-MTPB and B-NHTPB, respectively; the pseudo-second-order kinetic model described very well the adsorption of Orange II on modified bentonites. The non-linear Langmuir model provided the best correlation of experimental data, maximum adsorption of Orange II is 53.78 mg g−1 for B-NHTPB and 33.79 mg g−1 for B-MTPB. The thermodynamic parameters, such as free energy of adsorption (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were also determined and evaluated. From thermodynamic studies, it was deduced that the adsorption was spontaneous and exothermic.
    No preview · Article · Apr 2015 · Chemical Engineering Communications
  • Raquel Trujillano · Vicente Rives · Mohamed Douma · El Hossain Chtoun
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    ABSTRACT: A fast and unexpensive method to synthesize stannate pyrochlores has been set up. This method pursues to save time and energy. It is based in the increase of the reaction rate by microwave radiation. Two solids, Y2Sn2O7 and Eu2Sn2O7, with the pyrochlore structure, have been synthetized. Here we present the synthesis procedure and the characterization results.
    No preview · Article · Mar 2015 · Ceramics International
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    ABSTRACT: In the work “Iron oxide-pillared clay catalyzed the synthesis of acetonides from epoxides”, published in Catalysis Communications, three Fe-pillared clays are used as catalysts in the synthesis of acetonides. Catalytic results are interesting, but the authors do not report enough experimental evidences about the formation of Fe-pillared clays and, in fact, the formation of such solids seems not possible under the reported experimental conditions. This may induce strong confusion and even false conclusions for the readers of Catalysis Communications unfamiliar with this type of solids. The use of the internationally accepted terminology is strongly recommended.
    No preview · Article · Feb 2015 · Catalysis Communications
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    ABSTRACT: The preparation, characterization, and application in oxidation reactions and antibacterial activity of new biomimetic heterogeneous materials are reported. Brazilian Sao Simao kaolinite has been functionalized with Fe(III)-[meso-tetrakis(tetracarboxyphenyl)porphinato], [FeTCPP]. Clay functionalization with FeTCPP was confirmed by the amide bands observed in the FTIR spectrum, while UVvis spectroscopy revealed a red-shift of the characteristic Soret band of the iron porphyrin compared to the parent iron porphyrin in solution, an evidence of Fe-III-porphyrin -> Fe-II-porphyrin reduction. Both catalysts reveal complete selectivity for the epoxide in the epoxidation of cis-cyclooctene, while in the BaeyerVilliger (BV) oxidation of cyclohexanone reached 50% conversion (100% selectivity to e-caprolactone). The catalysts were recovered and used as antibacterial agents against various bacteria, with activity comparable to that of commercial products such as streptomycin. These results demonstrated that smart multifunctional hybrid organicinorganic materials that satisfy the demands of Green Chemistry with maximum usability and environmental compatibility can be designed via functionalization of kaolinite.
    Full-text · Article · Oct 2014 · The Journal of Physical Chemistry C
  • S. Albeniz · M.A. Vicente · R. Trujillano · S.A. Korili · A. Gil
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    ABSTRACT: The aim of this work was to synthesize and characterize the structural properties of the materials resulting from the combination of a synthetic saponite with several organic molecules, namely, Arquad 2HT-75, octadecylamine, 3-aminopropyltriethoxysilane, trimethyloctadecylammonium bromide and tetraethoxysilane, or combinations of them, and with or without the addition of HCl during synthesis. The ratios organic molecule/saponite and HCl/organic molecule were considered as synthesis variables. Structural characterization was based on X-ray diffraction (XRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and infrared spectroscopy (FTIR). The chemical composition of the materials was determined through X-ray fluorescence (XRF) and atomic absorption spectroscopy (AAS), and their morphology was analyzed through scanning electron microscopy (SEM). The values obtained for the basal spacings were a function of the type and amount of the organic molecule. Otherwise, HCl did not significantly influence the basal spacing, but it had the capacity to significantly modify the morphology and the chemical composition of the samples. From the results found, the solids modified with tetraethoxysilane and 3-aminopropyltriethoxysilane were selected to incorporate various titanium precursors. These new organo-modified saponites were used in the formulation of PVC nanocomposites and their thermal behavior was evaluated at two temperatures (70 and 180 °C).
    No preview · Article · Sep 2014 · Applied Clay Science
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    ABSTRACT: New heterogeneous catalysts were prepared by immobilization of Me(II)-dipicolinate complexes (Me = Co, Mn or Ni) on kaolinite (Ka). The precursor material was kaolinite grafted with dipicolinic acid (dpa) obtained via melting of the acid. The catalysts were prepared by suspending the Ka-dpa precursors (lamellar or exfoliated) in Me2' solutions with a cation/ligand ratio of 1:3. The grafted complexes were characterized by thermal analyses, X-ray diffraction, UV/Vis and infrared spectroscopies, and transmission electron microscopy. The catalysts were tested in three reactions: (i) epoxidation of cis-cyclooctene to cis-cyclooctenoxide reaching 55% yield, with total selectivity to cyclooctenoxide; (ii) oxidation of cyclohexane, reaching 22% yield, with total selectivity towards cyclohexanone; and (iii) Fenton-like decolorization of the dyes metanil yellow, methylene blue and green light, reaching 70-100% decolorization, the maximum effectiveness being observed for methylene blue degradation. The high conversion in the oxidation reactions and the high levels of decolorization of dyes confirmed the versatility of these heterogeneous catalysts based on kaolinite.
    Full-text · Article · May 2014 · Catalysis Today
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    ABSTRACT: Hydrotalcites (HTC) and gallium-substituted hydrotalcites (HTC-10Ga) were prepared by co-precipitation and modified by impregnation with alkali (K and Cs) and alkaline-earth (Sr) metals. The materials were tested and screened for CO2 sorption at 573 K. The results indicate that the modification with potassium greatly enhanced the sorption capacity when compared with the original materials (both HTC and HTC-10Ga). An outstanding sorption capacity (2.01 mmol cm−3 at 1.08 bar) was obtained for the sample partially substituted with gallium and modified with potassium (HTC-10Ga–20K). Moreover, this material was also submitted to sorption–desorption cycles towards CO2 under low-pressure conditions (<0.0001–0.15 bar) to assess its use in cyclic operation. An average working capacity of 0.97 mmol cm−3 and 0.25 mmol cm−3 was obtained after repeated cycles at 573 K and 473 K, respectively. The sorption kinetics was assessed through uptake measurements, showing two parallel resistances, which were well described by the proposed model.
    No preview · Article · Apr 2014 · Separation and Purification Technology
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    ABSTRACT: Several naturally-occurring enzymes, like cytochromes P450, selectively oxidize different substrates under mild conditions, using molecular oxygen as oxidant. Such a feat is desirable for any industrial process. The synthesis of new catalysts that mimic the action of these enzymes has been targeted in the area of catalysis. Synthetic metalloporphyrins, particularly ironporphyrins, have been successfully used as biomimetic catalysts in numerous oxidation reactions in homogeneous media. However, their high cost and difficult recovery from the reaction medium make their large-scale utilization unviable. Catalyst heterogeneization is an alternative approach to overcome the typical problems of homogeneous catalysis, as heterogeneous catalysts can be reused, reducing costs. Furthermore, enzyme site isolation can be mimicked, improving the reaction selectivity. In this context, new matrices must be designed for immobilization of metalloporphyrins, to satisfy current demands such as the use of clean oxidants like hydrogen peroxide. Despite the many literature studies on heterogeneized metalloporphyrin catalysts, few works have reported on their efficiency and selectivity in the presence of this oxidant. In recent years, an increasing interest has been observed in the synthesis of multifunctional organic-inorganic hybrid materials that meet the requirements of Green Chemistry, i.e., materials that combine maximum usability with environmental compatibility, and that open a new way for the preparation of heterogeneous catalysts. In this context, we describe in this chapter the catalytic activity of ironporphyrins supported on functionalized clays in the oxidation of cyclohexanone, as a part of our ongoing search for novel systems that perform green oxidation reactions using bioinspired catalysts.
    No preview · Chapter · Jan 2014
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    ABSTRACT: We study the effect of oxidative impurities on the properties of graphene oxide and on the graphene oxide Langmuir-Blodgett films (LB). The starting material was grupo Antolín nanofibers (GANF) and the oxidation process was a modified Hummers method to obtain highly oxidized graphene oxide. The purification procedure reported in this work eliminated oxidative impurities decreasing the thickness of the nanoplatelets. The purified material thus obtained presents an oxidation degree similar to that achieved by chemical reduction of the graphite oxide. The purified and non-purified graphene oxides were deposited onto silicon by means of a Langmuir-Blodgett (LB) methodology. The morphology of the LB films was analyzed by field emission scanning microscopy (FE-SEM) and micro-Raman spectroscopy. Our results show that the LB films built by transferring Langmuir monolayers at the liquid-expanded state of the purified material are constituted by close-packed and non-overlapped nanoplatelets. The isotherms of the Langmuir monolayer precursor of the LB films were interpreted according to the Volmer's model.
    Full-text · Article · Dec 2013 · ChemPhysChem

Publication Stats

1k Citations
226.70 Total Impact Points

Institutions

  • 1993-2015
    • Universidad de Salamanca
      • • Department of Inorganic Chemistry
      • • Faculty of Pharmacy
      Helmantica, Castille and León, Spain
  • 2008
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire de Réactivité de Surface (LRS) (UMR 7197)
      Lutetia Parisorum, Île-de-France, France
  • 1994
    • University of Cordoba (Spain)
      • Department of Inorganic Chemistry and Chemical Engineering
      Cordoue, Andalusia, Spain