Showing papers on "Silica gel published in 2009"
TL;DR: Adsorption isotherms for pure carbon dioxide and water vapor on 5A and 13X zeolite beads and silica gel granules are reported in this article, where all pure component equilibria are described well by Toth isotherm with parameters having temperature dependence.
Abstract: Adsorption isotherms are reported for pure carbon dioxide and water vapor on 5A and 13X zeolite beads and silica gel granules. These data were obtained using a volumetric method and cover the temperature ranges of (−45 to 175) °C for carbon dioxide and (0 to 100) °C for water. Also, pure carbon dioxide isotherms on silica gel at temperatures from (10 to 55) °C were measured using a gravimetric apparatus. All pure component equilibria are described well by Toth isotherms with parameters having temperature dependence. For carbon dioxide adsorption, zeolites 5A and 13X have similar loadings and show a much higher capacity than silica gel. However, for water vapor, zeolite 13X has a slightly higher capacity than zeolite 5A. Both zeolites have very good adsorption capacities for water vapor at low pressures but lose their advantages to silica gel when water pressures are high.
290 citations
TL;DR: In this article, the authors presented the dynamic modeling of a single effect two-bed adaption chiller utilizing the composite adsorbent "CaCl 2 confined to KSK silica gel" as an adsorbant and water as adsorbate, which is based on the experimentally confirmed adsorption isotherms and kinetics data.
209 citations
TL;DR: The removal of Co(II) and Ni(II), ions from contaminated water was investigated using silica gel materials functionalized with both ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic Acid (DTPA).
165 citations
TL;DR: In this article, the authors reported the synthesis of mesoporous silica xerogels in high purity from bagasse ash using NaOH solution and showed that the adsorption capacity was better for high-purity silica compared with low purity.
160 citations
TL;DR: Replacement of up to 88 mol % of the silicon from tetramethoxyorthosilicate with silicon derived from BTMSH and VTMS during the making of silica gels improves the elastic behavior in some formulations of the cross-linked aerogels, as evidenced by measurement of the recovered length after compression of samples to 25% strain.
Abstract: The effect of incorporating an organic linking group, 1,6-bis(trimethoxysilyl)hexane (BTMSH), into the underlying silica structure of a styrene cross-linked silica aerogel is examined. Vinyltrimethoxysilane (VTMS) is used to provide a reactive site on the silica backbone for styrene polymerization. Replacement of up to 88 mol % of the silicon from tetramethoxyorthosilicate with silicon derived from BTMSH and VTMS during the making of silica gels improves the elastic behavior in some formulations of the cross-linked aerogels, as evidenced by measurement of the recovered length after compression of samples to 25% strain. This is especially true for some higher density formulations, which recover nearly 100% of their length after compression to 25% strain twice. The compressive modulus of the more elastic monoliths ranged from 0.2 to 3 MPa. Although some of these monoliths had greatly reduced surface areas, changing the solvent used to produce the gels from methanol to ethanol increased the surface area in one instance from 6 to 220 m(2)/g with little affect on the modulus, elastic recovery, porosity, or density.
158 citations
TL;DR: In this paper, the performance of an adsorption desalination (AD) system in two-bed and four-bed operational modes is evaluated in terms of key performance parameters namely, specific daily water production (SDWP), cycle time, and performance ratio (PR).
151 citations
TL;DR: A solid phase extraction method using the new sorbent has been developed to separate and concentrate trace amount of uranium (VI) from aqueous samples for the measurement by spectrophotometry method using Arsenazo III reagent.
132 citations
TL;DR: Results indicate that magnesium influences the formation and the evolution of the newly formed layers, and it promotes the dissolution of the silica network and increases the thickness of thesilica gel layer formed conventionally prior to the apatite-like layer.
Abstract: Melt-derived glasses in the system SiO(2)-CaO-Na(2)O-P(2)O(5) were synthesized pure or doped with magnesium from 0.4 to 1.2 wt %, for applications as biomaterials in bony surgery. This chemical element has been chosen because of its high physiological interest. Its introduction for different contents in melt derived glasses has never been studied. The bioactivity of glasses was assessed by immersion of the samples in the simulated body fluid solution. Changes in glass surface morphology and composition after immersion were evaluated by several physico-chemical techniques. The aim of this work was to characterize the formation of the apatite-like layer at the glass surface, after in vitro assays and to evaluate the kinetic reaction between the glass and the surrounding synthetic fluids. Results indicate that magnesium influences the formation and the evolution of the newly formed layers: (1) it promotes the dissolution of the silica network, (2) it increases the thickness of the silica gel layer formed conventionally prior to the apatite-like layer, and (3) it slows down the crystallization of the apatite layer. However, the intensity of these effects depends on the content of magnesium introduced in the glass matrix.
114 citations
TL;DR: By demonstrating differentiation of human monocytes into osteoclast-like cells, an important feature of the composite material regarding successful bone remodeling is fulfilled and its mechanical properties are changed significantly due to collagen addition.
108 citations
TL;DR: In this article, a mesoporous silica KSK with a saturated aqueous solution of Ca(NO 3 ) 2 was synthesized and its equilibrium with water vapor was studied by measuring sorption isobars and isosters at T ǫ = 30-150°C.
107 citations
TL;DR: In hydrophilic interaction chromatography (HILIC), best results are obtained with high concentrations of ACN, and retention increased by lengthening the carbon chain of ion-pair reagents supporting the RP mechanism as well.
Abstract: In hydrophilic interaction chromatography (HILIC), best results are obtained with high concentrations of ACN. In the framework of green chromatography and the present shortage and very high price of this hazardous solvent, reversing the stationary phase to apolar and the mobile phase to aqueous can be of interest for several applications. The features of the aqueous RP technique called per aqueous LC (PALC) are illustrated with the analysis of catecholamines, nucleobases, acids, and amino acids. The ca. three-fold higher viscosity of water compared to ACN has consequences on the shape of the Van Deemter plot. For dopamine (N = 26.450 on a 25 cm x 4.6 mm id, 5 microm bare silica column), a reduced plate height of 1.9 at an u(opt) of 0.3 mm/s was calculated. The plate number, however, strongly depends on pH and ionic strength. As in RP separations, retention is shortened by adding an organic modifier. In the framework of green chromatography, the biodegradable ethanol was used. On the other hand, retention increased by lengthening the carbon chain of ion-pair reagents supporting the RP mechanism as well.
TL;DR: In this article, a new precursor, methyltriethoxysilane (MTES), was used for synthesizing the silica aerogels having the novel properties as that of MTMS-based aerogel precursors.
TL;DR: In this article, the effect of variations of the anions and cations of ILs, the alkyl chain length on imidazolium cation and IL concentration in the reaction system on the pore structure and thermal stability of the silica gel materials was preliminarily studied.
TL;DR: The silica-MIP bind the original template 2,4-DCP with an appreciable selectivity over structurally related compounds, and the molecular recognition of 2,3-dichlorophenol was analyzed in detail.
TL;DR: In this article, a new Pb-II-imprinted amino-functionalized silica gel sorbent was synthesized by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction of trace Pb(II) prior to its determination by inductively coupled plasma optical emission spectrometry.
Abstract: A new Pb(II)-imprinted amino-functionalized silica gel sorbent was synthesized by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction of trace Pb(II) prior to its determination by inductively coupled plasma optical emission spectrometry. The Pb(II)-imprinted amino-functionalized silica gel sorbent was characterized by Fourier transform infrared spectroscopy. Compared to non-imprinted polymer particles, the ion-imprinted polymers had higher selectivity and adsorption capacity for Pb(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Pb(II) was 19.66 and 6.20 mg g−1, respectively. The largest selectivity coefficient of the Pb(II)-imprinted sorbent for Pb(II) in the presence of Cd(II) was over 450. The relative selectivity (α
r) values of Pb(II)/Cd(II) were 49.3 and 46.3, which were greater than 1. The distribution ratio (D) values of Pb(II)-imprinted polymers for Pb(II) were much larger than that for Cd(II). The detection limit (3σ) was 0.20 μg L−1. The relative standard deviation was 2.0% for 11 replicate determinations. The method was validated for the analysis three certified reference materials (GBW 08301, GBW 08504, GBW 08511), and the results are in good agreement with standard values. The method was also successfully applied to the determination of trace lead in plants and water samples with satisfactory results.
TL;DR: In this paper, the catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions.
Abstract: Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800 h⁻¹ and turnover numbers (TON) of up to 68
were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the
heterogeneous photocatalyst stops the reaction conversion
immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26 h⁻¹, TON of 280
and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts.
TL;DR: In this paper, two methods were used to age the silica gels derived from tetraethoxysilane (TEOS) by two-step sol-gel process: aging in 100°C-autoclave with TEOS/ethanol mixed solution and in pure ethanol at room temperature.
TL;DR: In this paper, high uniform submonolayer to multilayer thin films of titanium dioxide supported on high surface area silica gel have been synthesized by atomic layer deposition (ALD) using titanium tetrachlorid...
Abstract: Highly uniform submonolayer to multilayer thin films of titanium dioxide supported on high surface area silica gel have been synthesized by atomic layer deposition (ALD) using titanium tetrachlorid...
TL;DR: A new approach, which utilizes a room-temperature synthetic route for incorporating therapeutic drugs into the silica matrix, should improve the capability for targeting intracellular pathogens.
Abstract: We investigated the capability of biodegradable silica xerogel as a novel carrier of antibiotic and the efficacy of treatment compared to that with the same dose of free drug against murine salmonellosis. The drug molecules (31%) entrapped in the sol-gel matrix remained in biologically active form, and the bactericidal effect was retained upon drug release. The in vitro drug release profiles of the gentamicin from the xerogel and that from the xerogel-polyethylene glycol (PEG) were distinctly different at pH 7.4. A delayed release of gentamicin was observed from the silica xerogel network (57% in 33 h), and with the addition of 2% PEG, the release rate reached 90% in 33 h. Administration of two doses of the silica xerogel significantly reduced the Salmonella enterica serovar Typhimurium load in the spleens and livers of infected AJ 646 mice. The silica xerogel and xerogel-PEG achieved a 0.45-log and a 0.41-log reduction in the spleens, respectively, while for the free drug there was no reduction. On the other hand, silica xerogel and xerogel-PEG achieved statistically significant 1.13-log and 1.15-log reductions in the livers, respectively, while for the free drug the reduction was a nonsignificant value of 0.07 log. This new approach, which utilizes a room-temperature synthetic route for incorporating therapeutic drugs into the silica matrix, should improve the capability for targeting intracellular pathogens.
Book•
01 Jan 2009
TL;DR: Silica-based materials for advanced chemical applications as discussed by the authors have been used in a variety of applications, such as: Silica-Based Materials for Advanced Chemical Applications (SMLA).
Abstract: Silica-based materials for advanced chemical applications , Silica-based materials for advanced chemical applications , کتابخانه دیجیتال جندی شاپور اهواز
TL;DR: Continuous adsorption measurements show that silica aerogels are excellent adsorbents of BTEX vapours from waste gas stream.
TL;DR: In this paper, a self-assembling of a sol-gel network and silver nanoparticles was developed for cyanide detection, which exhibited high sensitivity, good reproducibility, and long-term stability.
TL;DR: In this paper, reaction of an isocyanide with an iminium ion intermediate, formed by reaction between an electron-poor 2-hydroxybenzaldehyde derivative and a secondary amine in the presence of silica gel proceeds smoothly at room temperature to afford benzo[b]furan derivatives in high yields.
TL;DR: Two new silica-based organic−inorganic hybrid materials (B104SGs and O 104SGs) doped with a binary mixture of imidazolium and phosphonium ionic liquids have been synthesized and used as sorbents in batch system for rare earths (RE) separation as discussed by the authors.
Abstract: Two new silica-based organic−inorganic hybrid materials (B104SGs and O104SGs) doped with a binary mixture of imidazolium and phosphonium ionic liquids have been synthesized and used as sorbents in batch system for rare earths (RE) separation. Imidazolium ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate (C4mim+PF6−) or 1-octyl-3-methylimidazolium hexafluorophosphate (C8mim+PF6−) acted as porogens to prepare porous materials and additives to stabilize extractant within silica gel. Trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (Cyphos IL 104), a low-molecular-mass organic gelator, can encourage the formation of porous silica materials and increase the rate of aggregation. Cyphos IL 104 not only acted as an excellent template for the preparation of silica sorbents but also as a bifunctional ionic liquid extractant (bif-ILE) for RE(III) extraction. By the electrostatic attraction between the SiO- groups and phosphonium cations along the surfaces of the silica gel, stable si...
TL;DR: In this article, three Schiff base ligands and their complexes were synthesized and characterized by infrared spectroscopy (IR), thermogravimetric analyses (TGA), nuclear magnetic resonance (NMR), elemental analysis and magnetic susceptibility apparatuses.
TL;DR: In this article, functional monomer acrylamide (AM) was grafted step by step onto the surface of silica gel particles using 3-methacryloxypropyl trimethoxysilane (MPS) as coupling agent and the grafted particle PAM/SiO 2 was prepared.
TL;DR: In this paper, the monomers of the compounds 6-phenyl-3-(3′-triethoxysilylpropyl)-1,3,5-triazinane-2,4-dione have been synthesized and coated on the surfaces of silica gel particles and cellulose.
TL;DR: Results showed that Cu2+ loaded on AMPS-silica could be desorbed in HNO3 solution, and the adsorbent properties remain stable after three adsorption-desorption cycles.
Abstract: A novel adsorbent (AMPS-silica) was synthesized by bounding AMPS (2-acrylamido-2-methylpropanesulfonic acid) onto silica surface, which functioned with gamma-methacryloxypropyltrimethoxysilane reagent. The adsorbent was characterized by nitrogen adsorption/desorption measurement, thermogravimetric analysis (TGA) and potentiometric titration analysis. The TGA result indicated that the surface modification reactions introduced some organic functional groups onto the surface of silica. The surface area of AMPS-silica was 389.7 m(2)/g. The adsorbent was examined for copper ion removal in series of batch adsorption experiments. Results showed that the adsorption of Cu(2+) onto AMPS-silica was pH dependent, and the adsorption capacity increased with increasing pH from 2 to 6. The adsorption kinetics showed that Cu(2+) adsorption was fast and the data fitted well with a pseudo second-order kinetic model. The adsorption of Cu(2+) onto AMPS-silica obeyed both Freundlich and Langmuir isotherms, with r(2) = 0.993 and r(2) = 0.984, respectively. The maximum Cu(2+) adsorption capacity was 19.9 mg/g. The involved mechanism might be the adsorption through metal binding with organic functional groups such as carboxyl, amino and sulfonic groups. Cu(2+) loaded on AMPS-silica could be desorbed in HNO(3) solution, and the adsorption properties remain stable after three adsorption-desorption cycles.
TL;DR: In this article, dry coating experiments were performed with two different processes using a high energy impact coater "Hybridizer" (Nara) and a high shear mixer "Cyclomix" (Hosokawa).
TL;DR: The ion-exchange binding of protonated weakly basic analytes on deprotonated carboxylate sites on methacrylate polymer monoliths has been increased by templating themonoliths with silica nanoparticles, proving to be useful for the preconcentration and separation of neurotransmitters by in-line solid-phase extraction-capillary electrophoresis.