Bogdan Biliński

The determination of the dispersion and polar free surface energy of quartz by the elution gas chromatography method

Abstract The adsorption isotherms of n-octane, n-propanol and n-butanol on brasilian quartz were determined by the elution gas chromatography method. From the isotherms, the horizontal orientation of the hydrocarbon molecules and the vertical orientation of the alcohol molecules on the quartz surface were confirmed. From the isotherms, the film pressure π max of the adsorbates was also determined. From the π max value for n-octane, the dispersion free surface energy γ s d of quartz was calculated; the result obtained agrees with the literature data. From the π max values for the alcohols, the polar component of the free surface energy γ s p of quartz was calculated. The values obtained were compared with γ s p values, calculated from the film pressure π max data for water and n-propanol, taken from the literature. Considerable differences in the calculated γ s p values were observed and possible reasons for this are discussed.

Confrontation of energetic changes in sulfur/n-alkane-water and sulfur/n-alkane-vapor systems

Abstract Adsorption isotherms of n -heptane, n -octane, and n -nonane on sulfur at 30°C were determined by elution gas chromatography. From the isotherms the film pressure values and next the surface free energy γ s d for sulfur were determined. These values obtained for sulfur/ n -alkane-vapor were confronted with the film pressure and γ s d for sulfur/ n -alkane-water system, determined by electrokinetic measurements at 20°C. The γ s d value for sulfur obtained by both methods are reasonably comparable. The same may be said with respect to the literature γ s d values from contact angle measurements. Possible reasons for the observed differences in the film pressure and γ s d values are discussed. The method of elution gas chromatography for energetic studies on solids with a small specific surface seems to be useful.

Some theoretical and experimental limitations in the determination of surface free energy of siliceous solids

Abstract The components of surface free energy of silica gel were calculated according to various theoretical approaches, and based on the data from different experimental methods (i.e., gas chromatography and thin column wicking). The results are compared, and widely discussed in terms of theoretical imperfections, accuracy of the liquid surface tension components data, as well as specific conditions (affecting the surface properties) implied by the used experimental method. Special attention was paid to adsorbed water layers. The differences in the results (especially those, dealing with donor–acceptor interactions) are discussed in terms of the mechanism of water vapour adsorption. The adsorbed water may provide an increase of electron-donor interactions of the surface.

Investigations on the adsorption properties and porosity of natural and thermally treated dolomite samples

Abstract Adsorption properties with respect to certain toxic substances as well as porosity investigations of raw and thermally modified dolomite are presented. After the partial decomposition of dolomite at 800°C a new so-called ‘dolomitic’ adsorbent of the calcium carbonate skeleton and pumice structure was obtained. Its physicochemical properties are significantly different from those of the raw material, e.g. the specific surface area increases 37 times and the adsorption capacity for SO2 increases approximately 15 times, which makes the new adsorbent useful in the protection of the environment.

Investigation of the surface free energy components of thermally treated controlled porosity glasses by inverse gas chromatography

Adsorption isotherms of n-octane and toluene were measured on thermally treated controlled porosity glasses (CPG) and on boron-coated silica gel (SG). From the isotherms the film pressure (π) for both adsorbates was determined. Based on extrapolated πmax values the dispersion (γdS) and the non-dispersion (γnS) components of the surface free energy for all the investigated materials were calculated. It was found that the changes in γdS caused by the surface modification were relatively small (∼ 4mJ/m2), while those of γnS were significant. The boron compounds decrease the γnS value from 145–160 to 37–55 mJ/m2. The dependences between δπ/δa and the adsorbed amount can give some suggestion about the adsorption mechanism and surface homogeneity. The presence of Na on the surface of both CPG and SG seems to be a more important factor for adsorption than that of boron. The significant changes in non-dispersion interactions were attributed to surface dehydroxylation, which may result from both the thermal treatment and the presence of boron on the surface.

A Gas-Adsorption study of the influence of a flotation collector on the polar/nonpolar surface properties of barite

Abstract A modified elution gas chromatography method was used to determine the adsorption isotherms of n-octane and n-propanol on a barite surface covered with oleic acid. The extrapolated film pressure ☎ max values of both adsorbates were determined from the adsorption isotherms, and then the dispersion and polar free surface energy values were calculated as a function of the surface coverage with oleic acid. The calculations were performed on the assumption that the ☎ max value equals the work of spreading or the work of immersion. The energetic changes induced by the collector were then correlated with the flotability of barite. It was found that the collector completely reduced the polar interactions of the mineral surface and this was the main reason of the high flotability of this polar mineral.

The changes in surface free energy and surface heterogeneity of controlled-porosity glasses

Abstract The adsorption energy distribution function was calculated according to the asymptotically corrected condensation approximation method from n-octane and toluene retention data for two thermally treated and rehydroxylated controlled-porosity glasses. Similar calculations were performed for a model series of silica gels, the surfaces of which were previously covered with boron and sodium compounds. Certain differences in surface site distributions were observed. The results for toluene were then correlated with changes in the surface free energy. Such correlations are presented separately for thermally treated and subsequently rehydroxylated materials. The results are discussed in terms of the differences in surface chemistry.

Influence of polyacrylamide on the surface free energy and wettability of a chernozem soil

Abstract Measurements of contact angles for glycerol; diidomethane and cis-decalin drops on the surface of a soil precovered with Magnafloc 455 film were made. The precovering process was performed in two different ways. In the first the soil sample was immersed in aqueous Magnafloc solutions, and in the second the same aqueous Magnafloc solutions were percolated through the soil bed. From results of these measurements and the use of the modified Young equation, the dispersion and nondispersion components of the surface free energy of the soil precovered with different amounts of Magnafloc were calculated. The wetting coefficient for water was also determined. On the basis of the measurements and calculations it was found that hydrophilization of the soil occurred, mainly by an increase of the nondispersion component of the surface free energy of the soil. This took place as a result of the adsorption of Magnafloc molecules. However, the dispersion component remained almost constants. It was also found that the wetting coefficient increased as a function of the concentration of Magnafloc in the adsorptive solution.

An estimation of surface free energy of galena

Abstract Adsorption isotherms of n-octane and n-propanol were determined on galena samples pretreated in various ways. Based on the values of maximal extrapolated film pressure π max for both adsorbates (obtained from the isotherms), the dispersion and non-dispersion components of surface free energy were calculated and discussed. The spreading adsorption films seemed the most probable on the galena surface. For the non-oxidized surface of galena the dispersion component was 70.2 mJ m −2 , while the non-dispersion component was only 3.7 mJ m −2 . The surface oxidation resulted in a decrease of the dispersion component to 50−-55 mJ m −2 and in an increase of the non-dispersion component to 13−-14 mJ m −2 . Certain changes of the surface free energy of galena were also stated, depending on the method of sample pretreatment. They probably resulted from a partial elimination of the oxidized layer or from other changes in the structure of this layer (e.g. recrystallization).

Pore size analysis by nitrogen adsorption and thermal desorption

Thermogravimetric analysis was applied to the characterization of the porosity of silica gel. Thermal desorption of liquids from silicas for column chromatography was measured. Benzene, n-hexane and carbon tetrachloride were used as liquid adsorbates. Pore size distributions for silica gels of differentiated porosity were determined on the basis of thermogravimetric curves using the Kelvin equation. Pore dimensions were corrected in respect to the surface film thickness estimated from adsorption isotherms of the same adsorbates measured above their boiling point. The resulting pore size distributions and total pore volumes were compared with those obtained from the nitrogen method.