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

Neurobehavioral, Cognitive, and Paroxysmal Disorders in the Long-Term Period of Pediatric Traumatic Brain Injury

The consequences of the traumatic brain injury (TBI) in children and adolescents represent a major medical and social problem, as TBI interferes in the normal processes of neuroontogenesis. Brain damage in TBI in children and adolescents occurs during the ongoing processes of its growth and maturation, and therefore the clinical course and outcomes may differ significantly from those in adults. Poor outcomes of TBI sustained in early childhood may be explained considerably by the timing of injury in a period of rapid brain and behavioral development. Thus, TBI has a negative impact on the cognitive function development, behavior, school education, and social skills acquisition. Cognitive and behavioral disorders in children and adolescents in the long-term period of TBI become more prominent in co-occurrence with paroxysmal disorders, including posttraumatic headaches, posttraumatic epilepsy, and subclinical epileptiform activity on the EEG. In general, a favorable outcome is possible in children more often than adults even after severe TBI, due to the high neuroplasticity of the developing brain. Therapeutic and rehabilitation measures in the long-term period of TBI in children and adolescents should be intensively carried out both in the first 12 months after TBI, when the most significant results from their use are expected, and in the long-term period, considering the ongoing processes of morpho-functional maturation and neuroplasticity mechanisms

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