P. Staszczuk

Equilibrium study of selected divalent d-electron metals adsorption on A-type zeolite

The objective of the presented study was to investigate the adsorption of Cu, Co, Mn, Zn, Cd and Mn on A-type zeolite. The isotherms for adsorption of metals from their nitrates were registered. The following adsorption constants K of metals were found: 162,890, 124,260, 69,025, 16,035, 10,254, and 151 [M(-1)] for Cu, Co, Mn, Zn, Cd, and Ni, respectively, for the concentration range 10(-4)-10(-3) M. On the other hand, the investigation of pH influence on the distribution constants of metals showed that the adsorption of metals proceeds essentially through an ion-exchange process, surface hydrolysis, and surface complexation. The supplementary results from DRIFT, scanning electron microscopy, and X-ray diffraction methods confirmed the presumption about the possible connection between the electronic structure of divalent ions and their adsorption behavior, showing that ions with d5 and d10 configurations such as Mn2+, Zn2+, Cd2+, with much weaker hydrolytic properties than Cu2+ and Ni2+, strongly interact with the zeolite framework and therefore their affinity to the zeolite phase is much stronger when compared with that of the Ni2+ ion, but at the same time not as strong as the affinity of the Cu2+ ion, the latter forming a new phase during the interaction with zeolite framework. For Zn2+, during inspection of the correlation between the proton concentration H/Al and zinc concentration Zn/Al on the zeolite surface, the formation of the surface complex [triple bond]S-OZn(OH) was proposed. A correlation between the heterogeneity of proton concentrations H/Al on Me-zeolite surfaces and the hydrolysis constants pKh of Me2+ ions was found.

Physicochemical properties of liquid-solid interfaces by means of controlled rate thermal analysis

Abstract This paper sums up the possible application of controlled rate thermal analysis methods to study liquid—solid interactions and the physicochemical properties of liquid films and solid surfaces, using mainly the programmed thermodesorption of liquid from the sample. The results prove the applicability of this approach in the determination of adsorption value, thermodynamic functions, properties of adsorbed layers and the heterogeneity of porous materials. One principal idea of these studies was to register the effects taking place in processes opposite to adsorption, i.e. in the controlled rate thermodesorption of liquids from solid surfaces. The method utilized the differential time and temperature weight-loss (DTG) dependences of the thermogravimetric (TGA) curves as well as the differential scanning calorimetry (DSC) curves obtained during cooling and heating at subambient and elevated temperatures. It can be concluded that thermal analysis is a simple, useful and effective method, besides its classical applications, in characterizing liquid—solid systems. The authors most important results have been evaluated and published, or submitted for publication, in this and other scientific journals over the last past decade.

Analysis of the energetic heterogenity of HgBa2Ca2Cu3O8+δ surfaces Q-TG and Q-DTG data

Energetic heterogeneity of adsorbents is conditioned by the differences in topology of adsorption centres, dispersion of pore sizes and other factors. This paper describes theoretical and experimental studies that demonstrate a method for estimation of the energetic heterogeneity of adsorbents by making use of the results from single thermogravimetry Q-TG and Q-DTG curves, recorded under quasi-equilibrium conditions, for preadsorbed liquid on a porous solid 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.

Effect of flotation reagents on hydration of pit-coal and limestone surfaces part I. Investigations of hydration layers on the surface of minerals and the role of diesel oil in the pit-coal cleaning process

Abstract The results of investigations into the hydration and dehydration of pure samples of pit-coal (from the Lublin Coal Basin) and limestone are presented. On the basis of these results, we have concluded that the adsorption capacity of these minerals depends on the physicochemical properties of the surface, and in particular on their surface area. We have confirmed the existence of the so-called bonded water on the surface, which modified the surface properties of the minerals investigated. The investigations of pit-coal samples covered with diesel oil show a large decrease in adsorption capacity of its surface that leads practically to an increase in the effectiveness of the cleaning process.

Determination of total heterogeneity and fractal dimensions of high-temperature superconductors

Using thermo-analytical and sorptometric methods physicochemical properties and especially surface heterogeneity of HgBa2Ca2Cu3O8+δ, (Hg-1223) was investigated. The desorption energy distribution was derived from mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption in quasi-isothermal conditions of pre-adsorbed n-octane and water vapour. It is shown that the superconducting Hg-1223 phase is highly sensitive to water vapours. The mechanism of water adsorption depends largely on the activation time. By water vapour saturation in a period of 90 min, physisorption takes place. Prolonged periods result in a chemical decomposition. From nitrogen ad- and desorption isotherms the fractal dimension of superconductors were calculated. A new approach is proposed to calculate fractal dimension from Q-TG curves.

Studies of the adsorbed water layers on solid surfaces by means of the thermal analysis special technique

The paper presents the thermogravimetric studies of water film properties on the solid surfaces using the programmed desorption under the quasi-isothermal conditions. The samples wetted in a different way before the measurements were heated under the suitable quasi-isothermal conditions of temperature increase in the derivatograph using a platinum labyrinth crucible in order to evaporate water films from the surface. During the measurements, the mass loss Q-TG and the differential Q-DTG curves were registered as a function of temperature and/or time which are characterized by the inflections showing individual stages of water desorption from the samples. On the basis of experimental data, the surface wetting mechanism and kinetics of the thermodesorption of water films, discontinuous properties of adsorbed water layers on porous surfaces, adsorption capacity of samples and nature of active sites (e.g. hydroxyl groups) have been presented. It was stated that this method could be successfully applied in the studies of adsorbed water films and surface wetting phenomena.

Hydration of the surface of pure sulphur covered with n-alkanes

Abstract This paper presents the results of an investigation of the kinetics of adsorption and desorption of water on the surface of pure sulphur covered with n-alkanes. Changes of thermodynamic functions depending on adsorption values, as well as activation energy of water molecules were determined. On the basis of these results the effect of n-alkanes on the thickness of water layers formed on modified sulphur samples was shown. The mechanism of water adsorption here gives much information on the mode of molecule bonding on the sulphur surface.

On the Adsorption of Chromium(VI) Ions on Dolomite and ‘Dolomitic Sorbents’

The sorption capability of raw and thermally treated dolomite samples with respect to toxic ions was estimated through the adsorption of chromium(VI) from aqueous solutions. The adsorption isotherms were shown to fit the well-known Freundlich equation. The results confirm the weak adsorption of chromium(VI) on raw dolomite relative to the other dolomite-derived sorbents. The influence of ionic strength on the adsorption was also determined.

Characterization of the Structural and Energetic Heterogeneity of Mesoporous Solid Surfaces from Q-DTG Data

This paper presents the first evaluation of the pore-size distribution and energy distribution of butanol on a silica gel surface on the basis of one experimental run. The Q-TG mass loss and the first derivative Q-DTG mass loss curves of n-butanol thermodesorption from a silica gel sample were made with a Derivatograph Q-1500 D (MOM, Hungary), using an analyser equipped with an automatic ultraslow procedure and a special crucible capable of maintaining the quasi-isothermal heating procedure to increase the resolution of thermal analysis. A numerical procedure was developed for evaluation of the mesopore-size distribution and energy distribution functions of liquids preadsorbed on the mesoporous surfaces from special thermal analysis techniques. This is based on a condensation approximation to treat the kinetics of liquid thermodesorption from solids. A preliminary example is presented of application of the above approach to a quantitative description of the structural and energetic heterogeneities of silica gel surfaces on the basis of a single Q-DTG curve of n-butanol thermodesorption under quasi-isothermal conditions.