Adsorption Properties Of Silica Research Articles

Tuning the Mechanical and Adsorption Properties of Silica with Graphene Oxide

AbstractSilica and graphene oxide (GO) were synthesized by modified Stöber and Hummer’s methods, respectively. Silica/GO composite powders of different compositions were obtained by introduction of GO sheets in between silica particles through a hydrothermal synthesis. Composites were characterized by Fourier transform infrared spectroscopy, X‐ray diffraction analysis, and scanning and transmission electron microscopy. Density measurements were performed with a pycnometer and chemical analyses of powders were performed by energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies. Composite powders showed an improvement in the Cu2+ ion adsorption property relative to pure silica. Composite powders were further consolidated at 1200 °C under 50 MPa pressure in vacuum by pulsed electric current sintering. Transparency in the UV/Vis region, the electrical conductivity, and the toughness of consolidated samples were altered by varying the GO content in the starting materials. Studies suggest that the use of GO as a reinforcing agent not only improves the mechanical properties of transparent silica ceramic, but also improves the electrical conductivity and adsorption properties of silica.

The enhancement in photocatalytic activity of bismuth modified silica and bismuth silicate nanofibers

We investigated photocatalytic and adsorption properties of silica (SiO2), bismuth (Bi) modified silica and bismuth silicate (Bi4(SiO4)3) nanofibers. Nanofiber average diameter was ~150nm and length was several micrometers. The bandgap of SiO2 decreased with increased Bi content and its value was 3.7eV for Bi4(SiO4)3. The Bi-modified photocatalyst (nanofibers) exhibited enhanced degradation efficiency as compared to pure nanofibers. The pseudo first order kinetic model explained the photocatalytic kinetics of the photocatalyst with rate constants of 0.081min−1 and 0.406min−1 for SiO2 and Bi4(SiO4)3 nanofibers, respectively.

Preparation and Characterization of Textural and Energetic Parameters of Common and Functionalized SBA-15 Mesoporous Silicas

A set of SBA-15 ordered mesoporous silicas presenting different surface acidities was obtained by organo-functionalization. Amino and sulphonic groups were attached onto the silica surface in order to determine the influence of organo-functionalization with acidic and basic moieties on the adsorption properties of silica. Cephalexin, an antibiotic molecule characterized by its zwitterionic nature, was selected as the adsorbate. The obtained matrices were characterized by scanning electron microscopy, energy dispersive X-ray analysis and nitrogen adsorption isotherms at 77 K. Enthalpies of immersion into water, benzene and cephalexin solutions were measured by immersion calorimetry, and the cephalexin adsorption capacities of the different matrices were also determined. The structure of SBA-15 was conserved in the functionalized samples despite a noticeable reduction in the BET surface area, pore volume and pore size. It was found that the inclusion of amino groups promoted interaction between the adsorben...

Textural and adsorption properties of silica modified with germanium(IV) oxide

Nitrogen low-temperature adsorption-desorption shows that the incorporation of germanium(IV) oxide into a silicate matrix under the conditions of the sol-gel transition gives rise to the formation of silica with a uniform mesoporous texture that has a predominating pore diameter of about 4 nm.

A gas-chromatography study of adsorption properties of silica modified by stable nickel nanoparticles obtained in reverse micelles under γ-radiation

Stable nano-sized nickel particles are prepared using the radiation-chemical synthesis in reverse micelles. Adsorption properties of raw silica (silochrome, S-120), the silochrome modified by a micelle-forming compound (AOT), and the silochrome modified by the nano-sized nickel particles are studied using gas chromatography method. The retention times for different test-compounds at different temperatures are determined for these adsorbents. Specific retention volumes of the test-compounds, as well as the thermodynamic adsorption characteristics, are determined. After the modification, the initial adsorption heat for n-hydrocarbons increases, which points out to the higher surface roughness of the modified samples. For the nickel-nanoparticle-modified silica, the contribution of specific interactions of polar compounds is less than that for the unmodified silica; this can be explained by screening the active centers (OH-groups) of the silica gel by the metal nanoparticles. The silica polarity decreases after the modification. The gas chromatography method allows detecting the difference in the properties of nanocomposites containing Ni- and NiO-nanoparticles.

Adsorption Properties of Silica towards Poly(Ethylene Oxide) as a Function of pH Studied by Spin-Labelling

Poly(ethylene oxide) chains spin labelled at their free end were adsorbed on amorphous silica and put into contact with buffers of different pH. The Electron Paramagnetic Resonance spectrum has a shape very sensitive to the Brownian motion of the free radical and exhibits composite lines characteristic of two environments: loops and tails protruding into solution with a fast motion; trains adsorbed on the solid surface with a restricted motion. Both components were analysed and the rotational correlation times and the two populations of labels were plotted as a function of pH and temperature. The chains are progressively desorbed as both increase due to the weaker hydrogen bounding with the reactive silanol groups present at the surface. Therefore a molecular picture of the chains at the interface can be gained.

Adsorption Properties of Silica with Chemically Bonded Amino and Guanidino Groups

The influence of the non-homogeneity of the silica support and the nature and amount of modifier employed on the adsorption properties of materials with chemically bonded amino and guanidino groups was studied by means of gas chromatography (GC), adsorption measurements under static conditions and IR spectroscopy. The results indicate that adsorbents coated with a polymer film of amino groups have a nearly uniform surface. These adsorbents can be used for GC investigations and for the separation of polar compounds, including organic bases.

The influence of grafted functional groups on the adsorption properties of silica

The adsorption properties of silica gel with grafted aminopropyl and guanidinoethanethiol (GET) groups were studied by the techniques of adsorption under static conditions and gas chromatography. It was shown that molecules capable of forming hydrogen bonds are adsorbed on all modified samples more weakly than on the initial silica gel. The grafting of GET radicals on the surface results in a noticiable increase in the dispersion interaction with adsorbed molecules. Calculation of the contributions of molecular groups to the constant of adsorption equilibrium showed that the thermodynamic characteristics of adsorption on aminosilochromes and aminosilicas with a polymeric layer of the modifying agent have similar values. Such adsorbents can be used for investigation of polar compounds, including organic bases.