Adam W. Marczewski

Adsorption of asphaltenes from toluene on mineral surface

Abstract Undesirable adsorption of asphaltenes on rock minerals was studied. Asphaltenes are an important component of crude oil, being also natural surfactant stabilising water/crude oil emulsions. Owing to their chemical nature, asphaltenes are able to associate, form micelles and create a surface charge at the interface. Asphaltenes may be adsorbed on rock reservoir from the organic solvents in crude oil and as an organic colloid, they can adsorb electrolyte ions from aqueous solution. In order to simulate natural conditions we used asphaltenes from local drills, toluene as solvent and several typical oxides and carbonate rock components or minerals as adsorbents. Our study included natural Brazilian quartz, dolomite, calcite and kaolin, as well as pure oxides: Fe 2 O 3 and TiO 2 . The typical shape of asphaltene adsorption isotherms was obtained for all systems studied with the characteristic ‘steps’ which indicate changes in the state of asphaltene molecules in the solution and at the mineral surface. Those changes are related to the asphaltene association and further formation of hemimicelles and micelles.

Analysis of kinetic Langmuir model. Part I: Integrated kinetic Langmuir equation (IKL): a new complete analytical solution of the Langmuir rate equation.

In the article, a new integrated kinetic Langmuir equation (IKL) is derived. The IKL equation is a simple and easy to analyze but complete analytical solution of the kinetic Langmuir model. The IKL is compared with the nth-order, mixed 1,2-order, and multiexponential kinetic equations. The impact of both equilibrium coverage θ(eq) and relative equilibrium uptake u(eq) on kinetics is explained. A newly introduced Langmuir batch equilibrium factor f(eq) that is the product of both parameters θ(eq)u(eq) is used to determine the general kinetic behavior. The analysis of the IKL equation allows us to understand fully the Langmuir kinetics and explains its relation with respect to the empirical pseudo-first-order (PFO, i.e., Lagergren), pseudo-second-order (PSO), and mixed 1,2-order kinetic equations, and it shows the conditions of their possible application based on the Langmuir model. The dependence of the initial adsorption rate on the system properties is analyzed and compared to the earlier published approximate equations.

A new isotherm equation for single-solute adsorption from dilute solutions on energetically heterogeneous solids

A new isotherm equation is proposed for describing single-solute adsorption from dilute solution on energetically heterogeneous solids. This equation comprises all isotherm equations being an extension of simpleLangmuir isotherm to single-solute adsorption on heterogeneous solids. The phenol adsorption data from dilute aqueous solutions on activated carbon are studied by using this new equation.ZusammenfassungEs wurde eine neue Isothermengleichung für die Adsorption aus verdünnten Einzelkomponentenlösungen auf energetisch heterogenen Festkörpern vorgeschlagen. Diese Gleichung schließt alle bisherigen Isothermengleichungen in sich ein, die Verallgemeinerungen der einfachenLangmuir-Isotherme für Adsorption auf heterogenen Festkörpern sind. Es wurden Daten der Adsorption von Phenol aus verdünnten Wasserlösungen auf aktivierte Kohle unter Verwendung der neuen Gleichung untersucht.

Application of the SAXS method and viscometry for determination of the thickness of adsorbed polymer layers at the ZrO2-polymer solution interface.

The authors studied the influence of the molecular weight of polyacrylic acid (PAA) and polyacrylamide (PAM), solution pH and ionic strength, and the background electrolyte type on adsorption and the thickness of polyelectrolyte adsorption layers formed on ZrO(2) surface. Carboxyl groups distributed along PAA and PAM chains were shown to be responsible for their interface conformation, which directly influences the thickness of the adsorbed polyelectrolyte layers. Bonding of macromolecules with solid surface occurs through the hydrogen bridges of these groups. Two methods were applied to determine the PAA and PAM adsorption layer thickness on ZrO(2), i.e., SAXS (small angle X-ray scattering) and viscometry. Despite some limitations of the SAXS method resulting from the relationship between the size of solid pores, polymer molecular weight, and conformation of the adsorbed macromolecule, all obtained SAXS results were very close to those calculated from viscometry data.

TheLangmuir-Freundlich equation in adsorption from dilute solutions on solids

Correlation between parameters obtained from the signle-solute and bisolute adsorption data by means of theLangmuir-Freundlich equation has been studied.ZusammenfassungDie Korrelation zwischen den bei Anwendung derLangmuir-Freundlich-Gleichung erhaltenen Adsorptionsparametern für Einzel- und Binärkomponentenlösungen wurde untersucht.

Adsorption of asphaltenes from toluene on typical soils of Lublin region

Adsorption of asphaltenes on soils is one of the important problems, though largely underestimated, in environment protection of Lublin region. Asphaltene adsorption properties affect the way the contamination spreads in soil. Analysis of this phenomenon may help in localisation and elimination of oil spills. The asphaltenes studied were obtained from local drills (Swidnik near Lublin, Poland). In our previous paper, we investigated adsorption of asphaltenes from toluene on rock components (quartz, dolomite, calcite, kaolin as well as pure iron and titanium oxides). In order to simulate the natural oil spill conditions, we used toluene as solvent and typical soils from Lublin region as adsorbents (black earth, peat soil, lessive soil, brown soil, sandy podsolised soil, pararendzina soil). Main physicochemical properties of these soils were reported. Moreover, basic adsorption properties (nitrogen adsorption, adsorption of surfactants from water solutions, acidity, etc.) of several soil fraction were studied. We decided to use only certain mineral fractions with highest adsorption capacity, as other fractions have limited impact on total adsorption. Adsorption on soil fraction gives also some insight into relative importance of various soil components on summary soil properties. The results of adsorption measurements are described in terms of physical adsorption on heterogeneous solids. # 2002 Published by Elsevier Science B.V.

Energetic heterogeneity and molecular size effects in physical adsorption on solid surfaces

Abstract A simple model of adsorption processes involving simultaneously adsorbent heterogeneity and adsorbate molecule size is presented. The considerations concern adsorption from the gas as well as liquid phases on solids characterized by different surface topographies. Relationships between energy distribution functions and molecular size are derived and the form of the isotherm equation is discussed. The theoretical considerations are illustrated by some model calculations.

Effect of adsorbate structure on adsorption from solutions

Adsorption of benzene derivatives of various chemical properties from dilute aqueous solutions on the Norit activated carbons is investigated. The experimental systems are analyzed in terms of adsorption theory on energetically heterogeneous solids. The relations between the optimization isotherm parameters, i.e. equilibrium constants and heterogeneity parameters, and the solute properties, e.g. number, character and position of functional groups are discussed.

Physical adsorption of gases on energetically heterogeneous solids I. GeneralizedLangmuir equation and its energy distribution

A generalizedLangmuir equation is proposed for describing the monolayer adsorption of single gases on heterogeneous solids. The special cases of this equation are:Langmuir-Freundlich, Tóth andFreundlich type adsorption isotherms. The energy distribution function corresponding to this equation produces all types of simple energy distributions, i.e., symmetrical distribution, decreasing exponential distributions and asymmetrical distributions showing widening in the directions of low and high adsorption energies.ZusammenfassungEs wird eine generalisierteLangmuir-Gleichung zur Beschreibung der einlagigen Adsorption eines einzelnen Gases auf heterogenen Feststoffen beschrieben. Die speziellen Fälle dieser Gleichung sind:Langmuir-Freundlich-, Tóth- undFreundlich-Typ der Adsorptionsisotherme. Die Energieverteilung, die dieser Gleichung entspricht, gibt alle Typen einer einfachen Verteilung wieder, z. B. eine symmetrische Verteilung, eine abfallende exponentielle Verteilung und asymmetrische Verteilungen mit Erweiterung in die Richtung von niedriger oder hoher Adsorptionsenergie.

Adsorption and desorption kinetics of benzene derivatives on mesoporous carbons

Adsorption and desorption of benzoic and salicylic acids and phenol from a series of synthesized mesoporous carbons is measured and analyzed. Equilibrium adsorption isotherms are best described by the Langmuir–Freundlich isotherm. Intraparticle diffusion and McKay’s pore diffusion models, as well as mixed 1,2-order (MOE), integrated Langmuir kinetic equation (IKL), Langmuir–Freundlich kinetic equation and recently derived fractal-like MOE (f-MOE) and IKL models were compared and used to analyze adsorption kinetic data. New generalization of Langmuir kinetics (gIKL), MOE and f-MOE were used to describe desorption kinetics. Analysis of adsorption and desorption half-times shows simple relation to the size of carbon pores.