Raquel Trujillano

Universidad de Salamanca, Helmantica, Castille and León, Spain

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Publications (60)91.01 Total impact

  • Catalysis Today 01/2014; 227:105–115. · 2.98 Impact Factor
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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).
    Applied Clay Science 01/2014; · 2.34 Impact Factor
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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.
    Separation and Purification Technology 01/2014; 127:202–211. · 2.89 Impact Factor
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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.
    ChemPhysChem 10/2013; · 3.35 Impact Factor
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    Alba Álvarez, Raquel Trujillano, Vicente Rives
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    ABSTRACT: Ni–Ga layered double hydroxides with the hydrotalcite-like structure have been prepared by coprecipitation of the metal cations with NaOH or by urea hydrolysis; the use of different aging treatments, under air, reflux and or microwave radiation, permits to modify their chemical composition and textural properties. Slight variations of the different parameters in the aging treatments, namely, pressure (atmospheric or autogenous), heating con-ditions (conventional or microwave) and time, have been tested to develop a suitable method to obtain solids with tailored characteristics. Original and calcined solids have been fully characterized by means of PXRD, FT-IR, TG–DTA, S BET and particle size distribution measurements. After calcination, well-dispersed oxides with a high specific surface area have been obtained.
    05/2013;
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    ABSTRACT: Polymer/clay composites have several uses in fields such as engineering, agriculture, ceramics, surface coatings, absorbent materials, pharmaceuticals or catalysis. Polysaccharides, such as alginate and its acid derivatives, are biocompatible and biodegradable polymers, effective in the production of adsorbent systems, for encapsulation and controlled release of active ingredients such as drugs and fertilizers. In this work, alginate polysaccharide and alginic acid were used to form composites with laponite, both with the original clay or with clay previously functionalized with 3-aminopropyltriethoxysilane. The properties of the composites prepared from laponite or functionalized laponite and alginic acid or alginate were compared. The interaction of laponite with alginic acid leads to composites with strong disorder in the clay structure. In all cases, composites with high contents of polysaccharides, with good thermal and mechanical properties, are obtained. Laponite-derived composites showed high adsorption capability for Cr(III) and methylene blue from aqueous medium. Copyright © 2012 Society of Chemical Industry
    Polymer International 07/2012; 61(7). · 2.13 Impact Factor
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    ABSTRACT: The immobilization of Fe(III) picolinate and Fe(III) dipicolinate complexes on kaolinite furnished heterogeneous catalysts, whose catalytic activity was evaluated. The precursor materials were kaolinite grafted with picolinic (Ka-pa) and dipicolinic (Ka-dpa) acids obtained by melting of the pyridine carboxylic acids. To obtain the catalysts Fe(Ka-pa)-n and Fe(Ka-dpa)-n (n = 1, 2, or 3 is the ligand/Fe ratio), the precursors were suspended in Fe3+ solutions with cation/ligand ratios of 1:1, 1:2, or 1:3. The resulting materials were characterized by thermal analyses (simultaneous TG/DTA), X-ray diffraction, UV/vis and infrared spectroscopies, and transmission electron microscopy. The grafted complexes were employed as heterogeneous catalysts in the epoxidation of cis-cyclooctene to cis-cyclooctenoxide and in the oxidation of cyclohexane to cyclohexanol and cyclohexanone at ambient temperature and pressure. Hydrogen peroxide was used as oxygen donor at a catalyst/oxidant/substrate molar ratio of 1:300:100. Fe(Ka-pa)-n catalysts were very efficient for cis-cyclooctene epoxidation (38% conversion). For cyclohexane oxidation, Fe(Ka-dpa)-n was 100% selective for cyclohexanone formation, with substrate conversion of 14%. This last series of catalysts was also very effective in the Baeyer–Villiger reaction, with 60% substrate conversion and 100% selectivity for ξ-caprolactone. After reuse (5 times), the catalysts still led to high substrate conversion.
    Catalysis Today 06/2012; 187(1):135–149. · 2.98 Impact Factor
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    ABSTRACT: The catalytic efficiency of takovite-aluminosilicate-chromium catalysts obtained by adsorption of Cr(3+) ions from aqueous solutions by a takovite-aluminosilicate nanocomposite adsorbent is reported. The adsorbent was synthesized by the coprecipitation method. The catalytic activity of the final Cr-catalysts depended on the amount of adsorbed chromium. (Z)-cyclooctene conversion up to 90% with total selectivity for the epoxide was achieved when the oxidation was carried out with hydrogen peroxide, at room temperature. After five consecutive runs, the catalysts maintained high activity, although after the sixth reuse, the epoxide yields strongly decreased to 35%. The catalysts were also efficient for cyclohexane oxidation, reaching up to 18% conversion, with cyclohexanone/cyclohexanol selectivity close to 1.2. On the whole, their use as catalysts gives a very interesting application for the solids obtained by adsorption of a contaminant cation such as Cr(3+).
    ACS Applied Materials & Interfaces 04/2012; 4(5):2525-33. · 5.01 Impact Factor
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    ABSTRACT: This work reports the application of a natural clay and an alumina-pillared clay as adsorbents for the removal of a basic dye, Methylene Blue, from aqueous solutions. The intercalation and pillaring processes improve the adsorption capacity of the montmorillonite. The adsorption kinetics of the dye has been studied in terms of pseudo-first-order and pseudo-second-order models. The equilibrium data are mathematically modelled using Freundlich, Langmuir and Sips isotherm adsorption models.
    Desalination and water treatment 01/2012; 39:316-322. · 0.85 Impact Factor
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    ABSTRACT: Saponites containing divalent Mg, Ni, or Fe as octahedral cations and trivalent Al and Fe substituting Si in the tetrahedral sheet were synthesized using microwave radiation. Saponite with a high specific surface area was obtained in all the syntheses, although Fe-Al saponite crystallized was impurified by Fe2O3 and analcime. The catalytic activity of the solids for the epoxidation of (Z)-cyclooctene by hydrogen peroxide was tested, the solids obtained being highly active (conversion up to 8.8%, and 100% selectivity to the epoxide).
    Applied Clay Science 08/2011; 53(2):326-330. · 2.34 Impact Factor
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    ABSTRACT: Luminescent hybrid materials derived from kaolinite appear as promising materials for optical applications due to their specific properties. The spectroscopic behavior of terbium picolinate complexes covalently grafted on kaolinite and the influence of the secondary ligand and thermal treatment on luminescence are reported. The resulting materials were characterized by thermal analysis, element analysis, X-ray diffraction, infrared absorption spectroscopy, and photoluminescence. The thermogravimetric curves indicated an enhancement in the thermal stability up to 300 °C for the lanthanide complexes covalently grafted on kaolinite, with respect to the isolated complexes. The increase in the basal spacing observed by X-ray diffraction confirmed the insertion of the organic ligands into the basal space of kaolinite, involving the formation of a bond between Al-OH and the carboxylate groups, as evidenced by infrared spectroscopy. The luminescent hybrid material exhibited a stronger characteristic emission of Tb(3+) compared to the isolated complex. The excitation spectra displayed a broad band at 277 nm, assigned to a ligand-to-metal charge transfer, while the emission spectra presented bands related to the electronic transitions characteristic of the Tb(3+) ion from the excited state (5)D(4) to the states (7)F(J) (J=5, 4, and 3), with the 4→5 transition having high intensity with green emission.
    ACS Applied Materials & Interfaces 03/2011; 3(4):1311-8. · 5.01 Impact Factor
  • Miguel A. Vicente, Raquel Trujillano, Vicente Rives
    Applied Clay Science - APPL CLAY SCI. 01/2011; 52(1):190-191.
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    ABSTRACT: The use of specific characterization techniques, namely Thermal Analysis, Near Infrared Spectroscopy, Ultraviolet–Visible Spectroscopy, Electron Paramagnetic Resonance, Mössbauer Spectroscopy and Neutron Scattering, in the characterization of pillared clays is reviewed. Special emphasis is placed in the information provided by each of these techniques in the characterization of pillared clays.
    Applied Clay Science - APPL CLAY SCI. 01/2011; 53(2):97-105.
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    ABSTRACT: A novel reactive solid containing amine groups was prepared by functionalization of the Brazilian São Simão kaolinite with tris(hydroxymethyl)aminomethane, designated TRIS. The functionalization involved refluxing of the molten TRIS in the presence of kaolinite previously intercalated with dimethylsulfoxide (DMSO). TRIS effectively displaced DMSO from the clay mineral interlayer, giving rise to Al–O–C bonds, thereby forming a hybrid organic–inorganic matrix. The resulting material was characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and C and N elemental analysis. The X-ray diffractograms revealed the intercalation of DMSO, and subsequently TRIS. The thermogravimetric curves of the kaolinite samples functionalized with TRIS indicated that the materials were thermally stable up to 250 °C. Displacement of the bands due to interlayer hydroxyl groups in the infrared absorption spectra and the presence of vibration bands due to NH2 groups at 3349, 3331, 3290, and 1589 cm− 1 also confirmed functionalization of the kaolinite with TRIS.
    Applied Clay Science 01/2010; 48(3):516-521. · 2.34 Impact Factor
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    ABSTRACT: Functionalization of Brazilian São Simão kaolinite and Spanish Yunclillos saponite with the alkoxysilanes 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane is reported. The resulting hybrids were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and scanning electron microscopy, which demonstrated the effectiveness of the interlamellar grafting process. The X-ray diffractograms revealed incorporation of the alkoxide molecules into the interlayer space of the clays. The displacement of the stretching bands of interlayer hydroxyls in the infrared spectra of the modified kaolinites and the increased intensity of the Mg-OH vibrations in the spectra of the modified saponites confirmed the functionalization of the clays. The thermal behavior of the organoclays confirmed the stability of the hybrids, which was dependent on the clay used for preparation of the materials.
    Journal of Colloid and Interface Science 01/2010; 341(1):186-193. · 3.17 Impact Factor
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    ABSTRACT: The synthesis of saponites with Mg2+ as octahedral cation by using microwave radiation and their modification by mechanical grinding as a new way of synthesis of these materials were studied. The effect of time of irradiation during the microwave-assisted synthesis, and of the time of grinding during the further mechanical treatments was considered. Microwave radiation allowed obtaining saponites with structural formulae very close to the theoretical one and good ordering and properties employing short times of irradiation. Mechanical grinding induced the breakage of particles and the ordering of the layers, that is, smaller particles were formed, but they became much better oriented along the c direction than those existing in the as-synthesized saponites.
    Applied Clay Science - APPL CLAY SCI. 01/2010; 48(1):32-38.
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    ABSTRACT: In this chapter, the use of pillared clays as catalysts in green oxidation reactions is considered. Several catalytic oxidation reactions have been selected, and special attention is given to the reaction products and to the yields achieved.
    01/2010;
  • Pillared Clays and Related Catalysts: , ISBN 978-1-4419-6669-8. Springer Science+Business Media, LLC, 2010. 01/2010;
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    ABSTRACT: Two series of mixed oxides with formula [Eu2−xMx][Sn2−xMx]O7−3x/2 (M=Mg or Zn) have been synthesized. The study by X-ray diffraction and Fourier transform infrared spectroscopy shows that the solids obtained are new non-stoichiometric solid solutions with the pyrochlore type structure. For both series a decrease of the cell parameter is observed when the degree of substitution, x, increases. The structural refinements (X-ray studies) were achieved in the space group Fd-3m, no. 227 (origin at center -3m) by using the Fullprof software. The Rietveld refinements show that the divalent cations M2+ (Mg2+, Zn2+) substitute isomorphically for Eu3+ and Sn4+ ions producing vacancies in the anionic sublattice.
    Materials Research Bulletin - MATER RES BULL. 01/2010; 45(1):29-33.
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 25(43).

Publication Stats

177 Citations
91.01 Total Impact Points

Institutions

  • 1993–2014
    • Universidad de Salamanca
      • Department of Inorganic Chemistry
      Helmantica, Castille and León, Spain
  • 2008
    • Universidad Pública de Navarra
      • Departamento de Física
      Pamplona, Navarre, Spain
    • Complutense University of Madrid
      Madrid, Madrid, Spain