Gregorio Guadalupe Carbajal Arizaga

Publications (6)11.9 Total impact

• Article: Intercalation of an oxalatooxoniobate complex into layered double hydroxide and layered zinc hydroxide nitrate.

  Gregorio Guadalupe Carbajal Arizaga, José Eduardo Ferreira da Costa Gardolinski, Wido Herwig Schreiner, Fernando Wypych
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  ABSTRACT: A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH(4)[NbO(C(2)O(4))(2)(H(2)O)(2)]2H(2)O. In a similar way, the layered zinc hydroxide nitrate, Zn(5)(OH)(8)(NO(3))(2)2H(2)O, was synthesized, preexpanded with azelate ions ((-)OOC(CH(2))(7)COO(-)), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV-vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix.
  Journal of Colloid and Interface Science 12/2008; 330(2):352-8. · 3.07 Impact Factor
• Article: Cu2+ ions as a paramagnetic probe to study the surface chemical modification process of layered double hydroxides and hydroxide salts with nitrate and carboxylate anions.

  Gregorio Guadalupe Carbajal Arizaga, Antonio Salvio Mangrich, Fernando Wypych
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  ABSTRACT: A layered zinc hydroxide nitrate (Zn5(OH)8(NO3)2.2H2O) and a layered double hydroxide (Zn/Al-NO3) were synthesized by coprecipitation and doped with different amounts of Cu2+ (0.2, 1, and 10 mol%), as paramagnetic probe. Although the literature reports that the nitrate ion is free (with D3h symmetry) between the layers of these two structures, the FTIR spectra of two zinc hydroxide nitrate samples show the C2v symmetry for the nitrate ion, whereas the g ||/A || value in the EPR spectra of Cu2+ is high. This fact suggests bonding of some nitrate ions to the layers of the zinc hydroxide nitrate. The zinc hydroxide nitrate was used as matrix in the intercalation reaction with benzoate, o-chlorobenzoate, and o-iodobenzoate ions. FTIR spectra confirm the ionic exchange reaction and the EPR spectroscopy reveals bonding of the organic ions to the inorganic layers of the zinc hydroxide nitrate, while the layered double hydroxides show only exchange reactions.
  Journal of Colloid and Interface Science 05/2008; 320(1):238-44. · 3.07 Impact Factor
• Article: Chemical modification of zinc hydroxide nitrate and Zn–Al-layered double hydroxide with dicarboxylic acids

  Gregorio Guadalupe Carbajal Arizaga, Antonio Salvio Mangrich, José Eduardo Ferreira da Costa Gardolinski, Fernando Wypych
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  ABSTRACT: A zinc hydroxide nitrate (ZHN), Zn5(OH)8(NO3)2.2H2O, and a layered double hydroxide (LDH), Zn/Al-NO3 were doped with 0.2 mol% of Cu2+ during alkaline chemical precipitation. Both compounds were intercalated with adipate ((-)OOC(CH2)4COO(-)), azelate ((-)OOC(CH2)7COO(-)), and benzoate (C6H5COO(-)) ions through ion exchange reactions. Solid state 13C nuclear magnetic resonance spectroscopy showed only one signal of carboxylic carbon for adipate and azelate intercalated into LDH, indicating that the carboxylic ends of both acids were equivalent, whereas the signal split when the intercalation was into the ZHN matrix. The electron paramagnetic resonance (EPR) spectrum of copper in octahedral cation sites of LDH layers showed a Hamiltonian parameter ratio g ||/A ||=170 cm and, after intercalation of adipate, the change was not significant: g ||/A ||=174 cm. This result indicates that the carboxylate ions did not coordinate with copper centers. Nonetheless, the intercalation of azelate increased the ratio to g ||/A ||=194 cm, similar to the spectra of ZHN modified with adipate, g ||/A ||=199 cm, and azelate, g ||/A ||=183 and 190 cm, which are associated with the coordination of copper by weak carboxylate anion ligands. Copper occupies octahedral or tetrahedral sites in ZHN layers, and the EPR spectra indicate that the dicarboxylate anions reacted preferentially with octahedral sites, whereas benzoate reacted with both sites.
  Journal of Colloid and Interface Science 05/2008; 320(1):168-176. · 3.07 Impact Factor
• Article: Studies of the effect of molding pressure and incorporation of sugarcane bagasse fibers on the structure and properties of poly (hydroxy butyrate)

  Carlos Eduardo da Silva Pinto, Gregorio Guadalupe Carbajal Arizaga, Fernando Wypych, Luiz Pereira Ramos, Kestur Gundappa Satyanarayana
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  ABSTRACT: Poly (hydroxy butyrate) (PHB) is a biodegradable polymer that can be obtained from both renewable and synthetic resources. There have been many attempts to improve its structure and properties by different methods. This paper, while mentioning briefly PHB and sugarcane bagasse fibers, focuses on the effect of compressive/molding pressure on its structure and thermal properties with incorporation of sugarcane bagasse fibers, with and without steam explosion treatment. Thermal behavior (thermogravimetry and dynamic mechanical analysis), X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy methods were used to understand the changes in PHB resulting from the pressure and incorporation of fibers while scanning electron microscopy is used to understand the morphology of both the fiber and PHB.
  Composites Part A Applied Science and Manufacturing 40(5):573-582. · 2.69 Impact Factor
• Article: A new zinc hydroxide nitrate heterogeneous catalyst for the esterification of free fatty acids and the transesterification of vegetable oils

  Claudiney Soares Cordeiro, Gregorio Guadalupe Carbajal Arizaga, Luiz Pereira Ramos, Fernando Wypych
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  ABSTRACT: A new heterogeneous catalyst for the esterification of free fatty acids and the transesterification of vegetable oils is reported. The layered compound zinc hydroxide nitrate (Zn5(OH)8(NO3)2 · 2H2O) was very effective in the alcoholysis of palm oil and the esterification of lauric acid with m(ethanol), even when hydrated ethanol was used. Over the range of 100–140 °C, the ester yield was the highest at 140 °C, while the catalyst concentration had a much greater effect on ester yields than the molar ratio of alcohol to acid did. Total ester contents above 95 wt% were obtained in both reactions and 93.2 wt% glycerin streams were recovered as a result of methanolysis.
  Catalysis Communications.
• Article: Layered hydroxide salts: Synthesis, properties and potential applications

  Gregorio Guadalupe Carbajal Arizaga, Kestur Gundappa Satyanarayana, Fernando Wypych
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  ABSTRACT: Layered or two-dimensional (2D) compounds have recently attracted the attention of the scientific community due to their potential industrial applications. Their importance lies on the possibility of controlling and modifying the interlayer space in order to confer different chemical properties to the 2D assemblies. Modifications can be carried out by exfoliation/intercalation, anion exchange and/or layer surface grafting reactions. The structure of the layered hydroxide salts (LHS) derives from the brucite-like structure, where a fraction of the structural hydroxide groups is replaced by water molecules and anions, resulting in compounds formulated as M(OH)2-x(Am-)x/m·nH2O. This paper describes the synthesis, characterization, properties and possible applications of this fascinating class of compounds.
  Solid State Ionics. 178(15-18):1143-1162.