Effect of solution pH on the surface morphology of sol-gel derived silica gel

We have examined the effect of solution acidity on the textural characteristics of silica gels prepared by sol–gel synthesis using tetraethyl orthosilicate (TEOS) as a silica precursor and cetyltrimethylammonium bromide (CTAB) as a template. Using IR spectroscopy, we have studied micellar TEOS solutions and the synthesized silica gel samples. The results demonstrate that, in an alkaline medium in a water–ethanol solution, SiO2 experiences short-range ordering on the surface of micelles formed by CTAB molecules, whereas in an acid medium the process is not influenced by the presence of CTAB. Nitrogen porosimetry and electron microscopy data indicate that the silica gel obtained at pH 2 is microporous, with an average pore size of 2 nm. In an alkaline medium at pH 10, we obtained mesoporous SiO2 (18 nm) with a narrow pore size distribution and a specific surface area of 110 m2/g

Effect of solution pH on the surface morphology of sol-gel derived silica gel

We have examined the effect of solution acidity on the textural characteristics of silica gels prepared by sol–gel synthesis using tetraethyl orthosilicate (TEOS) as a silica precursor and cetyltrimethylammonium bromide (CTAB) as a template. Using IR spectroscopy, we have studied micellar TEOS solutions and the synthesized silica gel samples. The results demonstrate that, in an alkaline medium in a water–ethanol solution, SiO2 experiences short-range ordering on the surface of micelles formed by CTAB molecules, whereas in an acid medium the process is not influenced by the presence of CTAB. Nitrogen porosimetry and electron microscopy data indicate that the silica gel obtained at pH 2 is microporous, with an average pore size of 2 nm. In an alkaline medium at pH 10, we obtained mesoporous SiO2 (18 nm) with a narrow pore size distribution and a specific surface area of 110 m2/g

Effect of carrier properties on surface characteristics of sorbents modified with acetylacetonates Ni (II), Cu (II)

Sorbents based on Chromaton N-AW with layers of mesoporous silica gel modified with acetylacetonate nickel (II) and copper (II) were obtained. The porous structure of sorbents based on synthesized silica gel and industrial samples of Chromaton N, Silipore 075, Silochrom C-120 was studied. All studied samples are mesoporous. For sorbents based on commercially available Chromaton N, Silipore 075, and Silochrome 120, the mesopore dimensions vary in a wide range from 10 to 50 nm. For synthesized silica gel and chelate-containing sorbents, a narrower pore distribution is observed in the range of 5-15 nm, which indicates the uniformity of its surface. A comparative analysis of the effect of carrier properties on the acid-base properties of the surface of chelate-containing sorbents is carried out. The acid-base nature of the modifier is more pronounced in the case of synthesized silica gel by the sol-gel method

Effect of carrier properties on surface characteristics of sorbents modified with acetylacetonates Ni (II), Cu (II)

Sorbents based on Chromaton N-AW with layers of mesoporous silica gel modified with acetylacetonate nickel (II) and copper (II) were obtained. The porous structure of sorbents based on synthesized silica gel and industrial samples of Chromaton N, Silipore 075, Silochrom C-120 was studied. All studied samples are mesoporous. For sorbents based on commercially available Chromaton N, Silipore 075, and Silochrome 120, the mesopore dimensions vary in a wide range from 10 to 50 nm. For synthesized silica gel and chelate-containing sorbents, a narrower pore distribution is observed in the range of 5-15 nm, which indicates the uniformity of its surface. A comparative analysis of the effect of carrier properties on the acid-base properties of the surface of chelate-containing sorbents is carried out. The acid-base nature of the modifier is more pronounced in the case of synthesized silica gel by the sol-gel method

Adsorption properties of the surfaces of silica gels with grafted transition metal malonate complexes

Silica gels based on Silokhrom S-120 chemically modified with malonic ester chelates are studied using a set of physicochemical analytical techniques. The effect that a grafted layer of nickel, cobalt, or copper malonates has on the thermodynamic properties of adsorption of organic compounds from different classes on silica gel is investigated via gas chromatography. The test compounds are n-alkanes (C6–C9), chlorinated alkanes, alkenes, and adsorptives whose molecules exhibit different electron-donating and electron-withdrawing properties. Values for differential molar heat of adsorption change in standard differential molar entropy , and contributions to the energies of dispersive and specific interactions are calculated from experimental retention data for the considered adsorptives. The effect the metal ion of modifying malonate has on the parameters of thermodynamic retention is demonstrated

Adsorption properties of a silicagel surface with grafted transition metal acetylacetonate complexes

The adsorption properties of a Silipore 200 surface and chemically modified sorption materials containing nickel, cobalt, and copper acetylacetonates are studied via gas chromatography. n-Alkanes (C6–C9) and adsorbates, the molecules of which have different electron-donating and electron-acceptor properties, are used as test compounds. From experimental data on the retention of adsorbates; their differential molar adsorption heats q¯dif,1 ; changes in standard differential molar entropy ΔS¯S1,C ; and, for polar adsorbates, contributions Δq¯dif,1(specific) to the energy of dispersive and specific interactions, are calculated. The effect the metal ion in the structure of acetylacetonate has on the characteristics of thermodynamic retention is shown

Adsorption properties of a silicagel surface with grafted transition metal acetylacetonate complexes

The adsorption properties of a Silipore 200 surface and chemically modified sorption materials containing nickel, cobalt, and copper acetylacetonates are studied via gas chromatography. n-Alkanes (C6–C9) and adsorbates, the molecules of which have different electron-donating and electron-acceptor properties, are used as test compounds. From experimental data on the retention of adsorbates; their differential molar adsorption heats q¯dif,1 ; changes in standard differential molar entropy ΔS¯S1,C ; and, for polar adsorbates, contributions Δq¯dif,1(specific) to the energy of dispersive and specific interactions, are calculated. The effect the metal ion in the structure of acetylacetonate has on the characteristics of thermodynamic retention is shown

Determination of antioxidant composition in berry juices using solid phase extraction with copper phthalocyanine

The paper studies selective extraction of organic fractions with antioxidant activity from plant raw materials on the new sorbent with surface layer of phthalocyanine metal complexes and further HPLC determination. The possibility of sorption concentration of the antioxidant substances amount, which include mostly vitamin B groups, on the layer of copper phthalocyanine on polymer sorbent Polysorb-2. We determined antioxidant composition of honeysuckle, huckleberry and cowberry juice, namely, gallus, gentisinic, chlorogenic, caffeic, cumaric and p-methoxybenzoic acids; epicatechin and quercetine. Detection limit of this technique is 5 mg/l using copper phthalocyanine in the concentrator

Determination of antioxidant composition in berry juices using solid phase extraction with copper phthalocyanine

The paper studies selective extraction of organic fractions with antioxidant activity from plant raw materials on the new sorbent with surface layer of phthalocyanine metal complexes and further HPLC determination. The possibility of sorption concentration of the antioxidant substances amount, which include mostly vitamin B groups, on the layer of copper phthalocyanine on polymer sorbent Polysorb-2. We determined antioxidant composition of honeysuckle, huckleberry and cowberry juice, namely, gallus, gentisinic, chlorogenic, caffeic, cumaric and p-methoxybenzoic acids; epicatechin and quercetine. Detection limit of this technique is 5 mg/l using copper phthalocyanine in the concentrator