Cellulose aluminium oxide coated with organofunctional groups containing nitrogen donor atoms

A composite of cellulose and aluminium oxide, cel/Al2O3, was prepared and further modified with organofunctional groups by reacting with the coupling reagent (C2H5O)(3)SiL, where L represents -(CH2)(3)NH2, -(CH2)(3)NH(CH2)(2)NH2, -(CH2)(3)NH(CH2)(2)NH(CH2)(2)NH2 or -(CH2)(3)N(C3H3)N [-N(C3H3)N = imidazolyl radical], abbreviated to ap, enp, dienp and imp, respectively. The experimental preparation procedures were very reproducible and resulted in the following values for the amount of organofunctional groups grafted on cel/Al2O3 (average values in mmol g(-1)): cel/Al2O3/Si(ap) = 0.35; cel/Al2O3/Si(enp) = 0.30; cel/Al2O3/Si(dienp) = 0.25 and cel/Al2O3/Si(imp) = 1.0. The Al-27 MAS NMR spectra, which show an intensification of the area under the peak at 62 ppm due to Al in a tetrahedral environment, and the increase of the Al/C atomic ratios (determined from X-ray photoelectron spectra) after reaction with the coupling reagents indicate that Al atoms have migrated to the surface. This indicates that (C2H5O)(3)SiL is adsorbed on the matrix surface and reacts with the AlOH groups forming Al-O-Si bonds. The adsorption isotherms from ethanol solutions of FeCl3, CuCl2 and ZnCl2 were obtained at 298 K. The average stability constants were determined for each metal halide and the results indicated that the constants for the bi- and tridentate ligands, enp and dienp, are slightly higher than those for ap and imp, both monodentate ligands.10112526253

Calorimetric data on n-alkyldiamines intercalated into calcium phenylphosphonates

Layered crystalline calcium phenylphosphonate, as anhydrous Ca(HO3PC6H5)(2), and hydrated Ca(HO3PC6H5)(2)center dot 2H(2)O forms were used as hosts for intercalation of n-alkyldiamine molecules H2N(CH2) NHz (n=2-6) in water or 1,2-dichloroethane. The amount intercalated (n(f)) was followed batchwise at 298 +/- 1 K and the variation of the original interlayer distance (d) for hydrated calcium phenylphosphonate (1525 ppm) and anhydrous calcium phenylphosphonate (1751 ppm) was followed by X-ray powder diffraction. Linear correlations were obtained for d or n(f) as a function of the number of carbon atoms in the aliphatic chain (n(c)): d = (1424 +/- 65) + (108 +/- 14)n(c) and n(f) = (3.33 +/- 0.15) - (0.39 +/- 0.03)n(c), for the hydrated compound and d = (1643 +/- 60) + (108 +/- 12)n(c) and n(f) = (3.43 +/- 0.12) - (0.39 +/- 0.01)n(c), for the anhydrous compound. The exothermic enthalpies of intercalation increased with n(c), which derived from the monomolecular amine layer arrangement with longitudinal axis inclined by 58 to the inorganic sheets. The intercalation, followed by titration with amine at the solid/liquid interface with both matrices, gave the enthalpic/number of carbons correlation: Delta H degrees = - (0.54 +/- 0.12) - (1.10 +/- 0.09)n(c) and Delta H degrees = - (1.39 +/- 0.15) - (1.56 +/- 0.10)n(c), respectively. The exothermic enthalpic value increases with n, are more pronounced for the anhydrous compound. The Gibbs free energies are negative while positive entropic values favor intercalation in these systems. (C) 2005 Elsevier B.V. All rights reserved.4374167111412

Thermodynamics of the nickel and cobalt removal from aqueous solution by layered crystalline organofunctionalized barium phosphate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The available hydroxyl groups inside the lamellar cavity of barium phosphate (BaP) reacted with the silylating agents (RO)(3)Si(CH(2))(3)L(x) (L(1)= NH(2), L(2) = NH(CH(2))(2)NH(2), and L(3) = NH(CH(2))(2) NH(CH(2))(2)NH(2)), to yield organofunctionalized BaPSiL(1), BaPSiL(2) and BaPSiL(3) nanomaterials. The amounts of organofunctional groups covalently attached to the inorganic layer were (1.24, 1.46, and 1.23) mmol . g(-1), respectively. The basic nitrogen atoms attached to the distinct pendant organic chains adsorb divalent nickel and cobalt from aqueous solutions, as represented by well-established isotherms. The energetic effects caused by metallic cation interactions were determined through calorimetric titration at the solid/liquid interface and gave a net thermal effect that enabled enthalpy and equilibrium constant calculations. Complete thermodynamic results composed of exothermic enthalpy, negative free Gibbs energy and positive entropy result in a set of favourable cation/basic centre interactions, to indicate that these nanomaterials could be useful tools to eliminate undesirable cations from aqueous systems. (C) 2008 Elsevier Ltd. All rights reserved.4112125Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Synthesis and electrochemical properties of meldola blue intercalated into barium and calcium phosphates

Meldola blue (MLB) was strongly retained inside the cavity of host layered barium and calcium phosphates, without leaching, and the intercalated compounds were characterized through elemental analysis, X-ray power diffraction (XRD), infrared spectroscopy, scanning electron microscopy, phosphorus nuclear magnetic resonance and electrochemical measurements. The intercalated dye compound was incorporated into a carbon paste electrode and, by means of cyclic voltammetry, its electrochemical properties were investigated. Upon changing the pH of the solution between 2.5 and 7.0, the midpoint potential remained practically constant, giving near -0.020 and -0.019 V versus SCE for barium and calcium phosphates intercalated with MLB. This is not the usual behavior of MLB since its midpoint potential changes considerably in solution phase as the pH is changed. The modified electrodes have proven to be stable and electrocatalytically active for hydrazine oxidation at pH 6.0. (c) 2004 Elsevier B.V. All rights reserved.107144645

Calorimetric data on intercalation of some aromatic amines into barium phenylphosphonate at the solid/liquid interface

Layered crystalline hydrated barium phenylphosphonate, Ba(HO3PC6H5)(2) . H2O compound was employed as host for aromatic antines pyridine and alpha-, beta- and gamma-picolines, intercalation by using the batch method in ethanol at 298 I K, gave maximum amounts of (1.13, 0.76, 0.84 and 0.97) mmol . g(-1), respectively. The original interlamellar distance of 1532 pm increased after all intercalations. The thermochemical data were obtained on a differential isothermic microcalorimetric instrument by means of a titration procedure. From thermal effect data, the variation in enthalpy of intercalation for each system gave exothermic values of (-43.55 +/- 0.32, -2.36 +/- 0.04, -2.61 +/- 0.01 and -3.07 +/- 0.05) kJ . mol(-1) for the above sequence. The variation in enthalpic values for pyridine derivatives can be interpreted through the influence of steric hindrance associated with the methyl group attached to the heterocyclic ring. In addition to exothermic enthalpy, the spontaneous negative Gibbs free energy and the positive entropic values indicate favorable thermodynamic data for such intercalations. (C) 2004 Elsevier Ltd. All rights reserved.37324324

Layered crystalline barium phosphate organofunctionalized for cation removal

The available hydroxide groups inside the lamellar cavity of barium phosphate (BaP) were reacted with the silyating agents (RO)(3)Si(CH2)(3)L-x (L-1 = NH2, L-2 = NH(CH2)(2)NH2, and L-3 = NH(CH2)(2)NH-(CH2)(2)NH2), to yield organofunctionalized nanomaterials BaPSiL1, BaPSiL2, and BaPSiL3. The amount of organofunctional groups covalently attached to the inorganic layer was 1.24, 1.46, and 1.23 mmol g(-1), respectively. The basic nitrogen center atoms attached to the pendant organic chains adsorb FeCl3, CuCl2, and ZnCl2 from ethanol solutions to give well-established isotherms at 298 +/- 1 K. The results obtained in flow experiments showed a retention and recovery of ca. 100% of the metal ion with packed BaPSiLx columns from solution containing a mixture of these cations. The energetic effect caused by iron, copper, and zinc ion interactions was determined through calorimetric titration at the solid-liquid interface and gave a net thermal effect that enabled the calculation of the exothermic enthalpic values and the equilibrium constants. The complete thermodynamic data showed that the system has favorable enthalpic, Gibbs free energy, and entropic values. The cation removal properties were used with packed columns to successfully determine these cations in ethanol used as fuel sources.1892226223

Methylene blue intercalated into calcium phosphate - Electrochemical properties and an ascorbic acid oxidation study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Methylene blue (MB) was intercalated inside the cavity of a layered calcium phosphate host. The dye is strongly retained and not easily leached from the matrix. The intercalated dye material was incorporated into a carbon paste electrode and by means of cyclic voltammetry and amperometry, its electrochemical properties were investigated. In various electrolyte solutions, on changing the pH between 3 and 9, the midpoint potential remained practically constant at -0.15 V. This is not the usual behavior for MB, since it is known that in the solution phase the midpoint potential changes considerably with pH, indicating that, in the present case, methylene blue is a guest molecule intercalated inside the lamellar structure of the calcium phosphate. An electrode made with this material was used to study the electrochemical oxidation of ascorbic acid and then applied to commercial samples, with excellent agreement within the 95% confidence level. (C) 2007 Elsevier Masson SAS. All rights reserved.10911391144Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Layered crystalline barium phenylphosphonate as host support for n-alkylmonoamine intercalation

Layered barium phosphonate, synthesized by combining the metallic salt with a phenylphosphonic acid solution, yielded Ba(HO3PC6H5)(2)center dot H2O (BaPP), which gives the corresponding anhydrous compound on heating. n-Alkylmonoamines intercalation into the crystalline lamellar precursor resulted in compounds having the general formula Ba(HO3PC6H5)(2)center dot xH(2)N(CH2)(n)CH(3)center dot(1-x)H2O (n=1-5). The intense infrared bands in the 1160-695 cm(-1) interval confirmed the presence of the phosphonate groups attached to the inorganic layer, with sharp and intense peaks in X-ray diffraction patterns for both hydrated and anhydrous compounds. The thermogravimetric curves for both supports showed the release of water molecules and the organic moiety in distinct stages to yield a final Ba(PO3)(2) residue. An additional amine mass loss steps was observed for the corresponding aminated compounds. One isolated DSC peak found in the layered precursor compound contrasts by its absence in the anhydrous form and the P-31 NMR spectrum presented one peak for attached phenylphosphonate groups centered at 12.4 ppm. An increase in carbon and hydrogen percentages for intercalated compounds followed the amine size chain with a corresponding decrease in nitrogen percentage. The interlayer distance (d) correlates linearly with the number of carbon atoms (n(c)) of the alkylamine chains, d=1467+62n(c) and d=1688+60n(c), for the hydrated and anhydrous compounds, respectively, permitting inference of the interlayer distance for an unknown amine.5141671334