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

AbstractThis work describes a highly controlled post-grafting of mono and dicationic 4,4′-bipyridine alkoxysilane derivatives (Bipy+ and Bipy2+) onto the surface of an ordered mesoporous silica, SBA-15. The materials obtained are designated as SBA-15/Bipy+Cl− and SBA-15/Bipy2+Cl2-, 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/Bipy2+Cl2-. 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

The ion exchange properties and equilibrium constants of Li+, Na+ and K+ on zirconium phosphate highly dispersed on a cellulose acetate fibers surface

Highly dispersed zirconium phosphate was prepared by reacting celullose acetate/ZrO2 (ZrO2 = 11 wt%, 1.0 mmol g-1 of zirconium atom per gram of the material) with phosphoric acid. High power decoupling magic angle spinning (HPDEC-MAS) 31P NMR and X-ray photoelectron spectroscopy data indicated that HPO4(2-) is the species present on the membrane surface. The specific concentration of acidic centers, determined by ammonia gas adsorption, is 0.60 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+= 0.05, Na+= 0.38 and K+= 0.57. Due to the strong cooperative effect, the H+/Na+ and H+/K+ ion exchange is of non ideal nature. These ion exchange equilibria were treated with the use of models of fixed tridentate centers, which consider the surface of the sorbent as polyfunctional sorption centers. Both the observed ion exchange capacities with respect to the alkaline metal ions and the equilibrium constants are discussed by taking into consideration the sequence of the ionic hydration radii for Li+, Na+ and K+. The matrix affinity for the ions decreases with increasing the cations hydration radii from K+ to Li+. The high values of the separation factors S Na+/Li+ and S K+/Li+ (up to several hundreds) support the application of this material for the quantitative separation of Na+ and K+ from Li+ from a mixture containing these three ions.Fosfato de zircônio altamente disperso foi preparado reagindo acetato de celulose/ZrO2 (ZrO2 = 11 wt%, 1,0 mmol g-1 de átomo de zircônio por grama de material) com ácido fosfórico. Os dados de RMN 31P (HPDEC-MAS) com rotação de ângulo mágico desacoplado e Espectroscopia de Fotoelétron de raios-X indicam que a espécie HPO4(2-) está presente na superfície da membrana. A concentração específica de centros ácidos, determinada pela adsorção de gás amônia, foi de 0,60 mmol g-1. As capacidades de troca-iônica dos íons Li+, Na+ e K+ foram determinadas das isotermas de troca-iônica à 298 K e mostraram os seguintes valores ( em mmol g-1): Li+ = 0,05, Na+ = 0,38 e K+ = 0,57. Devido ao forte efeito cooperativo a troca-iônica de H+/Na+ e H+/K+ apresentou natureza não ideal. Esse equilíbrio de troca-iônica foi tratado com o uso de modelos de centros bi ou tridentados que considera a superfície do sorvente como centros de sorção polifuncionais. Tanto as capacidades de troca-iônica observadas com os respectivos íons metálicos alcalinos quanto as constantes de equilíbrio foram discutidas considerando a seqüência dos raios de hidratação iônicos para Li+, Na+ e K+. As afinidades para os íons diminuem com o aumento do raio de hidratação dos cátions, por ex. Li+< Na+ < K+ . Os altos valores dos fatores de separação de S Na+/Li+ e S K+/Li+ permitem aplicar este material para a separação quantitativa de Na+ e K+ de Li+ de uma mistura contendo esses três íons.5057Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Adsorption of metal ions on novel 3-n-propyl (methylpyridinium) silsesquioxane chloride polymers surface: study of heterogeneous equilibrium at the solid-solution interface

Polymers Si3Py+Cl- (A) and Si4Py+Cl- (B), 3-n-propyl (3-methylpyridinium) silsesquioxane and 3-n-propyl(4-methylpyridinium) silsesquioxane chlorides, respectively, were prepared by the sol-gel processing method. The ion exchange capacities (mmol g-1) were 0.90 and 0.81 for (A) and (B) respectively. Considering the reaction nSiPy+Cl-(s) + M2+(sln) + 2Cl-(sln) <IMG SRC="../img/a18setas.jpg" WIDTH=54 HEIGHT=15>(SiPy+)nMCl2+n n-(s), the values of the stepwise equilibrium constants obtained were: (A) CuII: logK(2)¹= 4.14(0.03), logK(2)²= 2.91(0.04); ZnII, logK(2)¹= 3.3(0.3), logK(2)²= 4.9(0.3); (B) CuII:logK(2)¹= 3.82(0.03), logK(2)²= 3.00(0.04); ZnII, logK(2)¹= 3.93(0.03), logK(2)²= 3.55(0.08), being K(2)¹ and K(2)² the equilibrium constants for adsorption of the species MCl4(2-) and MCl3-, respectively. For adsorption of ZnII on Si3Py+Cl-, K(2)² > K(2)¹, indicating positive cooperativity, i.e., the adsorption of MCl4(2-)enhances the adsorption of MCl3- species on the adsorbent surface. For the other cations, K(2)¹ > K(2)², indicating that adsorption of MCl4(2-)depresses the adsorption of MCl3-species, indicating negative cooperativity. <IMG SRC="../img/a18setas.jpg" WIDTH=54 HEIGHT=15

Cellulose acetate-Al2O3 hybrid material coated with n-propyl-1,4-diazabicyclo[2.2.2] octane chloride : preparation, characterization and study of some metal halides adsorption from ethanol solution

The preparation, characterization as well as the adsorption properties of MCl n (M= Fe(III), Co(II) and Cu(II)) from ethanol solutions by the new hybrid material cellulose acetate /Al2O3 coated with N-propyl-1,4 diazabicyclo [2.2.2] octane chloride group are described. The diamine is bonded to the cellulose acetate /Al2O3 surface by Al-O-Si covalent bonds and thus, the material obtained is chemically very stable and shows high adsorption capacity in adsorbing MCl n from ethanol solutions. When the material (designated as sigma-L+Cl-) comes into contact with the metal halide solutions, the salts diffuse into the substrate-solution interface as neutral species and are fixed in the form of the anionic complexes. The latter are held near the surface due to the electrostatic interactions with the positively charged centers ~L+. The adsorption capacities of the material (t, in mmol g-1) and its affinities to the metal halides were determined by analyzing the adsorption isotherms with the help of the model of fixed polydentate centers. The constants of the adsorption equilibria (beta, in L mol-1) were used as the quantitative characteristics of affinity. For the FeCl3 adsorption equilibrium <IMG SRC="/img/revistas/jbchs/v16n2/en_a04img01.gif">the specific concentration of the sorption centers <IMG SRC="/img/revistas/jbchs/v16n2/en_a04img02.gif">is equal to 1.42 and log beta11 = 3.14. The adsorption of CoCl2 and CuCl2 (MCl2) is described in a more complicated way: <IMG SRC="/img/revistas/jbchs/v16n2/en_a04img03.gif"> The following values of parameters were obtained: <IMG SRC="/img/revistas/jbchs/v16n2/en_a04img04.gif" > or = 0.20 and 0.115; log beta21 = 4.08 and 3.3 for CoCl2 and CuCl2 respectively

Cellulose acetate-Al2O3 hybrid material coated with N-Propyl-1,4-diazabicyclo [2.2.2] octane chloride: preparation, characterization and study of some metal halides adsorption from ethanol solution

The preparation, characterization as well as the adsorption properties of MCl n (M= Fe(III), Co(II) and Cu(II)) from ethanol solutions by the new hybrid material cellulose acetate /Al2O3 coated with N-propyl-1,4 diazabicyclo [2.2.2] octane chloride group are described. The diamine is bonded to the cellulose acetate /Al2O3 surface by Al-O-Si covalent bonds and thus, the material obtained is chemically very stable and shows high adsorption capacity in adsorbing MCl n from ethanol solutions. When the material (designated as sigma-L+Cl-) comes into contact with the metal halide solutions, the salts diffuse into the substrate-solution interface as neutral species and are fixed in the form of the anionic complexes. The latter are held near the surface due to the electrostatic interactions with the positively charged centers ~L+. The adsorption capacities of the material (t, in mmol g-1) and its affinities to the metal halides were determined by analyzing the adsorption isotherms with the help of the model of fixed polydentate centers. The constants of the adsorption equilibria (beta, in L mol-1) were used as the quantitative characteristics of affinity. For the FeCl3 adsorption equilibrium the specific concentration of the sorption centers is equal to 1.42 and log beta11 = 3.14. The adsorption of CoCl2 and CuCl2 (MCl2) is described in a more complicated way: The following values of parameters were obtained: or =0.20 and 0.115; log beta21 = 4.08 and 3.3 for CoCl2 and CuCl2 respectively.A preparação, bem como as propriedades de adsorção de MCl n (M=Fe(III), Co(II) e Cu(II)) de soluções etanólicas são descritas para um novo material híbrido acetato de celulose /Al2O3 recoberto com cloreto de N-propil-1,4 diazabiciclo [2.2.2] octano. A diamina está ligada à superfície do acetato de celulose/Al2O3 pela ligação covalente Al-O-Si e então, o material obtido é quimicamente muito estável e apresenta elevada capacidade de adsorção de MCl n de solução etanólica. Quando o material (designado como sigma-L+Cl-) entra em contacto com soluções do haleto metálico, os sais difundem na interface substrato-solução como espécies neutras e são fixadas na forma de complexos aniônicos. Estes são presos à superfície devido às interações eletrostáticas com a carga positiva dos centros ~L+. As capacidades de adsorção do material (t, em mmol g-1) e as duas afinidades pelo haletos metálicos foram determinadas analisando-se as isotermas de adsorção com o auxílio de um modelo de centros polidentados fixos. As constantes de equilíbrio da adsorção (beta, em mmol L-1) foram usadas como características de afinidade. Para o FeCl3, ao equilíbrio de adsorção a concentração específica dos centros de adsorção é igual a 1,42 e 0,115; log beta11= 3,14. A adsorção de CoCl2 e CuCl2 (MCl2) é descrita de uma forma mais complexa: Os seguintes valores dos parâmetros foram obtidos: ou =0,20 e 0,115; log beta21= 4,08 e 3,3, respectivamente para CoCl2 e CuCl2.147152Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

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: mSiO2/SiPy+Cl-+ MClz (SiO2/SiPy+)m[MCl(z+m)]m-, where the [MCl(z+m)]m- species adsorbed on the surface are FeCl4-, ZnCl4(2-), and CuCl4(2-). 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.26932-

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 Al(2)O(3), resulting in the organic-inorganic hybrid Cel/Al(2)O(3). Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH(2))(3)L (L=NH(2), NH(CH(2))(2)NH(2), NH(CH(2))(2)NH(CH(2))(2)NH(2), and N(2)C(3)H(3) (imidazole)), resulting in Cel/Al(2)O(3)/Si(CH(2))(3)NH(2) (1), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(2) (2), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(CH(2))(2)NH(2) (3), and Cel/Al(2)O(3)/Si(CH(2))(3)N(2)C(3)H(3) (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 FeCl(3), CuCl(2), and ZnCl(2) by Cel/Al(2)O(3)/Si(CH(2))(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.25431-

Probing Silica—Organic Hybrid Materials Using Small Probes: Simulation of Adsorption Equilibria Influenced by Cooperativity Effects

The property of non-ideality (cooperativity effects, energetic heterogeneity of binding centres) is often observed at probing surfaces by small ionic or molecular probes. A procedure based on the model of polydentate binding is recommended as a tool for detection and quantitative characterization of these effects. This procedure allows one to find objective estimations of effective sorption capacities and constants of adsorption equilibria. In this study, adsorption of small probes by two hybrid silica–organic materials has been studied. Ormosil with immobilized n-propylamine was probed with H + ions, and in addition, CoCl 2 adsorption from solutions of ethanol by silica chemically modified with 3-n-propyltrimethoxysilane-1-methylimidazolium chloride was also investigated. In both cases, the model of bidentate binding properly fitted the experimental data. This made it possible to determine the quantitative characteristics of adsorption equilibria and to arrive at conclusions on the cooperativity effects. Negative cooperativity effects are significant in adsorption of H + ions, while strong positive cooperativity affects CoCl 2 binding