Raquel Trujillano

Universidad de Salamanca, Helmantica, Castille and León, Spain

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Publications (70)198.08 Total impact

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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.
    Catalysis Today 05/2015; 246. DOI:10.1016/j.cattod.2014.09.019 · 3.31 Impact Factor
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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.
    ACS Applied Materials & Interfaces 05/2015; DOI:10.1021/acsami.5b01894 · 5.90 Impact Factor
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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.
    Chemical Engineering Communications 04/2015; 202(4). DOI:10.1080/00986445.2013.853291 · 0.79 Impact Factor
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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.
    Catalysis Communications 02/2015; 61. DOI:10.1016/j.catcom.2014.07.004 · 3.32 Impact Factor
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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.
    The Journal of Physical Chemistry C 10/2014; 118(42). DOI:10.1021/jp5077356 · 4.84 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 09/2014; 99. DOI:10.1016/j.clay.2014.06.014 · 2.70 Impact Factor
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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.
    Catalysis Today 05/2014; 227:105–115. DOI:10.1016/j.cattod.2013.09.031 · 3.31 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 04/2014; 127:202–211. DOI:10.1016/j.seppur.2014.03.007 · 3.07 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 12/2013; 14(17). DOI:10.1002/cphc.201300620 · 3.36 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.
    Applied Clay Science 05/2013; 80-81. DOI:10.1016/j.clay.2013.05.012 · 2.70 Impact Factor
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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). DOI:10.1002/pi.4196 · 2.25 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. DOI:10.1016/j.cattod.2011.11.029 · 3.31 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. DOI:10.1021/am300227z · 5.90 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 02/2012; 39:316-322. DOI:10.1080/19443994.2012.669181 · 0.99 Impact Factor
  • Catalysis Communications 01/2012; · 3.32 Impact Factor
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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 08/2011; 53(2):97-105. DOI:10.1016/j.clay.2010.09.018 · 2.70 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. DOI:10.1016/j.clay.2010.12.005 · 2.70 Impact Factor
  • Miguel A. Vicente, Raquel Trujillano, Vicente Rives
    Applied Clay Science 04/2011; 52(1):190-191. DOI:10.1016/j.clay.2011.02.015 · 2.70 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. DOI:10.1021/am2001086 · 5.90 Impact Factor
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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 10/2010; 25(43). DOI:10.1002/chin.199443026

Publication Stats

776 Citations
198.08 Total Impact Points

Institutions

  • 1993–2015
    • Universidad de Salamanca
      • • Department of Inorganic Chemistry
      • • Faculty of Pharmacy
      Helmantica, Castille and León, Spain
  • 2009
    • Universidade de Franca
      Franca, São Paulo, Brazil
  • 2008
    • Pierre and Marie Curie University - Paris 6
      • Laboratoire de Réactivité de Surface (LRS) (UMR 7197)
      Lutetia Parisorum, Île-de-France, France
    • Universidad Pública de Navarra
      • Departamento de Física
      Pamplona, Navarre, Spain
  • 1999
    • Universidad de Sevilla
      Hispalis, Andalusia, Spain