Aluminum phosphate dispersed on a cellulose acetate fiber surface - Preparation, characterization and application for Li+, Na+ and K+ separation

Cellulose acetate fibers with supported highly dispersed aluminum phosphate were prepared by reacting aluminum-containing cellulose acetate (Al2O3 = 3.5 wt.%; 1.1 mmol g(-1) aluminum atom per gram of the material) with phosphoric acid. Solid-state NMR spectra (CPMAS P-31 NMR) data indicated that HPO42- is the species present on the fiber surface. The specific concentration of acidic centers, determined by ammonia gas adsorption, is 0.50 mmol g(-1). The ion exchange capacities for Li+, Na+ and K+ ions were determined from ion exchange isotherms at 298 K and showed the following values (in mmol g(-1)): Li+ = 0.03, Na+ = 0.44 and K+ = 0.50. The H+/Li+ exchange corresponds to the model of the ideal ion exchange with a small value of the corresponding equilibrium constant K = 1.1 x 10(-2), Due to the strong cooperative effect, the H+/Na+ and H+/K+ ion exchange is non-ideal. These ion exchange equilibria were treated with the use of models of fixed bi- or tridentate centers, which consider the surface of the sorbent as an assemblage of polyfunctional sorption centers. Both the observed ion exchange capacities with respect to the alkaline metal ions and the equilibrium constants were discussed by taking into consideration the sequence of the ionic hydration radii for Li+, Na+ and K+. The matrix affinity order for the ions decreases as the hydration radii of the cations increase, i.e. Li+ > Na+ > K+. The high values of the separation factors SNa+/(Li+) and SK+/Li+ (up to several hundred) provide quantitative separation of Na+ and K+ from Li+ from a mixture containing these three ions. (C) 2002 Elsevier Science B.V. All rights reserved.477230531

Synthesis, characterization and metal adsorption properties of the new ion exchanger polymer 3-n-propyl(4-methylpyridinium) silsesquioxane chloride

The preparation and anion exchange properties of 3-n-propyl(4-methylpyridinium) silsesquioxane chloride polymer are described. This new polymer was prepared by the sol-gel processing method and is designated as SiPic(+)Cl(-). It is insoluble in water and showed an anion exchange capacity of 1.46 x 10(-3) molg(-1). The adsorption isotherms of ZnCl(2), CdCl(2) and HgCl(2) were determined from aqueous solutions and the adsorption equilibria simulations fit the model of fixed bidentate centers with the absence of lateral interactions and energetic heterogeneity between them. The metal ions diffuse into the solid solution interface and are dominantly present as MCl(4)(2-) species for Zn(II), MCl(4)(2-) and MCl(3)(-) species for Cd(II) and MCl(3)(-) species for Hg(II). (c) 2006 Elsevier Inc. All rights reserved.3031182

Adsorption of metal halides from ethanol solutions by a 3-n-propylpyridiniumsilsesquioxane chloride-coated silica gel surface

3-n-Propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl-, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl-. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmol g(-1). Metal halides, MClz [M = Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO(2)/SiPy+Cl- + MClz reversible arrow (SiO2/SiPy+)(m)[MClz+m](m-), where the [MClz+m](m-) species adsorbed on the surface are FeCl4-, ZnCl42-, and CuCl42-. Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures. (C) 2003 Elsevier Inc. All rights reserved.2691323

Simulation of adsorption equilibria on hybrid materials: Binding of metal chlorides with 3-n-propylpyridinium silsesquioxane chloride ion exchanger

The quantitative description of cooperativity effects at binding of low-molecular reagents with active reactive centers of hybrid materials requires the elaboration of convenient and reliable meaningful models and calculation procedures. The model of fixed polydentate centers was analyzed as a prospective tool for simulation of adsorption equilibria. The model was shown to be flexible and adaptive. At the theoretic foundations, it is equivalent or more general as compared with another approaches. The procedure for constructing the models fitting the experimental data. within their errors and the corresponding calculation tools were discussed. The special attention was paid to the problem of simultaneous determination of sorption capacities and equilibrium constants. To overcome this difficulty the strategy involving the fuzzy sets theory was proposed. The elaborated methods were used to characterize a new material, 3-n-propylpyridinium silsesquioxane chloride ion exchanger. Adsorption of Fe(III), Cu(II), Zn(II), Cd(II), and Hg(II) chlorides by the material from ethanol solutions was studied at 298 K. The material was found to possess a high affinity to metal chlorides. The sorption capacities of the material and the constants of adsorption equilibria were determined. The material demonstrates the following order of affinity: FeCl3 > CuCl2, HgCl2 > CdCl2 > ZnCl2. On the base of simulation, the negative cooperativity in the case of the CuCl2 adsorption was concluded, while adsorption of other chlorides is accompanied by the positive cooperativity. (c) 2007 Elsevier Inc. All rights reserved.3101475

Metal ions adsorption from ethanol solutions on ethylenediamine-modi fled poly(dimethylsiloxane) elastomeric network

An ethylenediamine-modified elastomeric network was obtained by the polycondensation reaction between poly(dimethylsiloxane), PDMS, with 2-aminoethyl-3-aminopropyltrimethoxysilane. The polymeric material was structurally characterized by its infrared spectrum and its solid state C-13 and Si-29 NMR. The Si-29 NMR peaks at -70 and -61 ppm correspond to the Si environments in CSi(OSi)(3) and Gi(OH)(OSi)(2) units respectively, and a peak at -24 ppm is associated with (C2Si(OSi)(2). Thermogravimetric analysis of the product showed good thermal stability and differential scanning calorimetry showed a glass transition temperature from 150 to 160 K, with no evidence of crystallization. From the adsorption isotherms of Fe(III), Ni(II) and Cu(II), from an ethanol solution at 298 K, onto the polymeric network, the equilibrium constants were calculated for the adsorption reactions of these metal ions at the solid-solution interface. The following stability constants, P, and the adsorption capacities, t(Q) (in mmol of metal per gram of the adsorbent) were determined: (a) Cu(II): log beta = 4.01 (0.03), t(Q) = 1.27 (0.02); (b) Fe(III): log beta = 3.49 (0.03), t(Q) = 1.45 (0.05); (C) Ni(II): log beta = 2.78 (0.06), t(Q) = 0.52 (0.05), where the numbers in parenthesis are the standard deviations. (C) 2008 Elsevier B.V. All rights reserved.32841699212

Determination of the constants of affinity of FeCl3, CuCl2, and ZnCl2 for a nitrogen-containing organosilane bonded on Al2O3-cellulose acetate hybrid material surface from ethanol solution

This work describes the preparation and characterization of a cellulose acetate fiber coated with Al2O3, resulting in the organic-inorganic hybrid Cel/Al2O3. Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH2)(3)L (L = NH2, NH(CH2)(2)NH2, NH(CH2)(2)NH(CH2)(2)NH2, and N2C3H3 (imidazole)), resulting in Cel/Al2O3/Si(CH2)(3)NH2 (1), Cel/Al2O3/Si(CH2)(3)NH(CH2)(2)NH2 (2), Cel/Al2O3/Si(CH2)(3)NH(CH2)(2)NH(CH2)(2)NH2 (3), and Cel/ Al2O3/Si(CH2)(3)N2C3H3 (4). The amounts of attached organofunctional groups were (in mmol per gram of the material) 1 = 1.90, 2 = 1.89, 3 = 1.66, and 4 = 1.35. The isotherms of adsorption of FeCl3, CuCl2, and ZnCl2 by Cel/Al2O3/Si(CH2)(3)L from ethanol solutions were obtained at 298 K. Accurate estimates of the specific sorption capacities and the heteregeneous stability constants of the immobilized metal complexes were determined with the aid of several computational procedures. It is shown that the sorptional capacities are much less than the concentrations of the attached organofunctional groups. As all sorption isotherms are fitted properly with the Langmuir isotherm equation, the effects of the energetic heterogeneity and the lateral interactions do not affect the chemisorption equilibria. The heterogeneous stability constants of the immobilized complexes are fairly high, which provides efficient removal of the metal ions from solutions by the hybrid materials. (C) 2002 Elsevier Science (USA).2541313

Surface modification with phosphoric acid of SiO2/Nb2O5 prepared by the sol-gel method: Structural-textural and acid sites studies and an ion exchange model

In this work, the structural and textural properties of the SiO2/Nb2O5 system prepared by the sol-gel method and then modified by phosphoric acid were studied. The different materials were prepared, with three different mol % Nb2O5 (2.5, 5.0, and 7.5 mol %), and calcined in the temperature range of 423-1273 K. BET specific surface area determinations, scanning electron microscopy connected to a X-ray emission analyzer, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used for the investigation. For the lowest temperature of calcination (423 K), the mesopores and micropores of the modified material were blocked, resulting in a decrease of the specific surface area compared to the S-BET values obtained for the SiNb matrix. Under intermediate temperatures of calcination (423-873 K), the modified material acquired textural stability. By XPS analysis, the presence of the dihydrogenphosphate species was identified, the P/Nb atomic ratios being independent of the thermal treatment. P-31 magic angle spinning NMR confirmed the XPS data and also showed that the chemical shift of the (H2PO4)(-) ions strongly depended on the crystallization degree of the Nb2O5. Structural thermal stability was also shown by the presence of Bronsted acid sites in the modified material calcined at high temperature (1273 K). The thermal stability is directly associated with obtainment of the same value for K+ exchange capacity (0.74 mmol g(-1), average value) for the modified materials calcined at 423 and 1273 K. The chemical analyses of phosphorus for the modified materials were made by using the inductively coupled plasma. The value was 0.36 mmol g(-1), corroborating the presence of (H2PO4)(-) ions. The ion exchange isotherms presented an S-shaped form characteristic of energetically heterogeneous ion exchangers, permitting application of a model of fixed polydentate centers, in which ion exchange took place.20208707871

Highly-controlled grafting of mono and dicationic 4,4 '-bipyridine derivatives on SBA-15 for potential application as adsorbent of CuCl2 from ethanol solution

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This work describes a highly controlled post-grafting of mono and dicationic 4,4'-bipyridine alkoxysilane derivatives (Bipy(+) and Bipy(2+)) onto the surface of an ordered mesoporous silica, SBA-15. The materials obtained are designated as SBA-15/Bipy(+)Cl(-) and SBA-15/Bipy(2+)Cl(2)(-), both possessing chloride as counter ion. The regular arrangement of uniform pores of this inorganic matrix is likely to ensure good accessibility to the active centers (electron acceptors) attached to the surface. The materials are excellent adsorbents due to the ability of the functional groups to retain copper chlorides on their surfaces as anionic complexes (CuCl2+nn-) in ethanol. From the adsorption results it was possible to probe the functional surface monolayer of the materials, which present a highly homogenous distribution of functional groups inside the ordered SBA-15 channels, with an exchange efficiency of 93% for SBA-15/Bipy(+)Cl(-) and 94% for SBA-15/Bipy(2+)Cl(2)(-). Both adsorbent materials are potentially useful in the pre-concentration and further analysis of Cu(II) present in trace amounts in ethanol, extensively used as an automotive fuel in Brazil. (C) 2012 Elsevier Inc. All rights reserved.384137142Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Ministry of Education and Science, Youth and Sport of Ukraine [0110U001453]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2009/12189-5]Ministry of Education and Science, Youth and Sport of Ukraine [0110U001453

Surface functionalization of SBA-15 and a nonordered mesoporous silica with a 1,4-diazabicyclo[2.2.2]octane derivative: Study of CuCl2 adsorption from ethanol solution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This work describes the preparation and characterization of postfunctionalized ordered (SBA-15) and nonordered (SMD) mesoporous silicas with n-propyl-1,4-diazoniabicycle[2.2.2]octane chloride (DbCl) moiety. The main interest is based on the fact that these materials are excellent adsorbents due to the ability of functional groups to retain copper chlorides on their surfaces as anionic complexes CuCl2+nn-. The specific surface areas (S-BET) and average pore diameters (d(pore)) for SBA-15 and SMD are SBA-15, S-BET = 944 m(2) g(-1), d(pore) = 9.0 nm; SMD, S-BET = 710 m(2) g(-1), d(pore) = 11 nm. On functionalization with DbCl, reductions in the specific surface areas of the resulting materials (SBA-15/DbCl and SMD/DbCl) are observed and the following functionalization degrees (phi) were determined: SBA-15/DbCl, S-BET = 247 m(2) g(-1), phi = 0.95 mmol g(-1); SMD/DbCl, S-BET = 83 m(2) g(-1), phi = 1.2 mmol g(-1). The adsorption equilibria of CuCl2 in ethanol were characterized, and the heterogeneous stability constants, beta(1) and beta(2), corresponding to formation of CuCl42- and CuCl3- anionic species adsorbed on the surface were found. Also, the effective sorption capacities (t(Q)) were determined: SBA-15/DbCl, log beta(1) = 4.46, log beta(2) = 7.10, t(Q) = 0.80 mmol g(-1); SMD/DbCl, log beta(1) = 4.95, log beta(2) = 7.52, t(Q) = 0.75 mmol g(-1). Regeneration of the adsorbents requires a very simple procedure consisting of their immersion in aqueous solution followed by immediate release to the solution phase of the Cu(OH2)(n)(2+) species, followed by chloride anions as the counterions. (C) 2011 Published by Elsevier Inc.3561248256Conselho 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)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP