Adsorption and chemisorption of galactose oxidase on silica surface

Experience accumulated over a number of years in developing of methods of immobilization of galactose oxidase from Fusarium graminearum on parent and modified silica matrices is analyzed. Sturdy adsorption of galactose oxidase on silica surface was observed, such heterogeneous specimens possessed by enhanced biocatalyst stability and activity as compared with enzyme solutions. Covalent immobilization of galactose oxidase was carried out on the amine-containing silicas activated by 2,4-tolylene diisocyanate and cyanuric chloride. It was also shown that in the presence of the substrate (galactose) enzyme chemisorption takes place on the surface on aminecontaining silica matrices. Immobilized preparations were successfully applied for analytical determination of galactose-containing carbohydrates (galactose, lactose, raffinose) in complex mixtures

Effect of precursor and surfactant nature on geometrical characteristics of mesoporous silicas

Bimodal mesoporous silicas and materials MCM-41 type were synthesized with the use as a template cationic surfactants distinguished by a length of the alkyl chain. Fumed silica, tetraethyl orthosilicate as well as of mixture these compounds were applied as a silicate precursor. Obtained samples have been characterized by the powder X-ray diffraction technique and adsorption measurements. Specific surface area, pore diameter, pore size distribution was determined from nitrogen ad(de)sorption isotherms at 77 K for the silicas prepared. The products with bimodal pore distribution have not ordered structure and contain macropores and mesopores, whose sizes are typical for MCM-41 materials. Effect of surfactant and precursor nature on the geometrical features of the ordered structure of MCM-41 type and bimodal porous materials was studied

Template Syntheses of Porous Silica Adsorbents with Spherical Particle Morphologies

The peculiarities of template syntheses of ordered porous silicas with spherical particle morphologies were investigated in alkaline and acidic media. The silicas obtained were characterized by nitrogen adsorption/desorption measurements, X-ray diffraction, scanning and transmission electron microscopies. Mesoporous silica matrices with high specific surface areas (450–1200 m 2 /g), an ordered pore structure and a spherical particle granulation of ca. 0.5 μm size were synthesized in alcohol/ammonia media. In acidic media, silica spheres with an average diameter of ca. 10 μm, a slightly ordered pore structure and a lower specific surface area (600 m 2 /g) were obtained

Methylene Blue Sorption Equilibria on Hydroxylated Silica Surfaces as Well as on Carbon–Silica Adsorbents (Carbosils)

The adsorption properties of hydroxylated silica gel as well as carbon–silica adsorbents (Carbosils) containing 5 and 18 w/w% carbon, both treated hydrothermally (with hydrogen peroxide solution) (HTT samples) and untreated, towards Methylene Blue (MB) were compared. The equilibrium adsorption of MB solutions of 6.5–7.0 × 10 −4 mol/l concentration and its dependence on pH were studied. At this concentration, ca. 30% of the adsorbent surfaces investigated were covered with MB molecules under optimal adsorption conditions. The presence of carbon deposits on the silica surface did not lead to a decrease in the adsorption capacity of Carbosils relative to that of hydroxylated silica. However, such deposits increased the resistance of the adsorbent towards the action of alkalis. Oxidation of the carbon deposit in the HTT process caused a further increase in this resistance. Hence, the adsorption mechanism of MB at equilibrium in individual systems of the type investigated can differ significantly. On the one hand, this mechanism is associated with the differing behaviour of silica over a wide range of pH relative to treated and untreated Carbosils and on the other hand with the specific properties of MB