The process by which progesterone in an ethanol solution is retained by Merck granular activated ... more The process by which progesterone in an ethanol solution is retained by Merck granular activated carbon involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (θ ) of the adsorbing surface and (1 − θ). Over the temperature range 10-40 • C, the specific adsorption rate varies from 5.8·10 −5 to 1.3·10 −4 s −1 . The thermodynamic activation functions for the process are H * = 41.6 kJ/mol and S * = −0.20 kJ/K· mol. The rate of the adsorption-desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent.
In the conditioning tasks of olive-tree a large amount of a woody residue is generated. Such a re... more In the conditioning tasks of olive-tree a large amount of a woody residue is generated. Such a residue has been traditionally used as a domestic fuel. In the last decades, however, this kind of use has lost importance and the preparation of activated carbons from olive-tree wood appears as an attractive alternative to valorize this by-product. In this study, the optimization of the chemical activation method with phosphoric acid for the production of activated carbon has been analyzed. The results obtained clearly show that samples prepared at 350 and 400°C exhibit a discrete porous development. On the contrary, when the carbonization temperature increases above 450°C the presence of a well-developed mesoporosity is observed. The mercury intrusion curves indicate that the samples exhibit a noticeably developed mesopore volume as well as a wide variety of mesopores ranging from 40 up to 1100 Å of diameter. If the appropriate conditions are used, it is possible to prepare activated carbons showing tailored properties in terms of micro-or mesoporous texture and surface area.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
The process by which progesterone in an ethanol solution is retained by four carbonaceous materia... more The process by which progesterone in an ethanol solution is retained by four carbonaceous materials involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (u ) of the adsorbing surface and (1(/u ). Over the temperature range 10 Á/40 8C, the specific rate constant varies from 5.29 )/10 (4 to 44.85 )/10 (4 s (1 . The formation of the activated species involved in the adsorption process is an endothermal, exoentropic step. The rate of the adsorption Á/desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent. #
In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon blac... more In this paper the adsorption process of a natural steroid hormone (progesterone) by a carbon black and a commercial activated carbon has been studied. The corresponding equilibrium isotherms have been analyzed according to a previously proposed model which establishes a kinetic law satisfactorily fitting the C versus t isotherms. The analysis of the experimental data points out the existence of two well-defined sections in the equilibrium isotherms. A general equation including these two processes has been proposed, the global adsorption process being fitted to such equation. From the values of the kinetic equilibrium constant so obtained, values of standard average adsorption enthalpy (DH ) and entropy (DS ) have been calculated. Finally, information related to variations of differential adsorption enthalpy (DH) and entropy (DS) with the surface coverage fraction (u) was obtained by using the corresponding Clausius-Clapeyron equations. #
The process by which progesterone in an ethanol solution is retained by Merck granular activated ... more The process by which progesterone in an ethanol solution is retained by Merck granular activated carbon involves a reversible mechanism that conforms to a kinetic equation of unity partial order in both the progesterone concentration in solution, the coverage fraction (θ ) of the adsorbing surface and (1 -θ). Over the temperature range 10-40 • C, the specific adsorption rate varies from 5.8•10 -5 to 1.3•10 -4 s -1 . The thermodynamic activation functions for the process are H * = 41.6 kJ/mol and S * = -0.20 kJ/K• mol. The rate of the adsorption-desorption process is primarily determined by diffusion of progesterone molecules in the pores of the sorbent.
The textural characterization of a series of activated carbons prepared from olive stones, by car... more The textural characterization of a series of activated carbons prepared from olive stones, by carbonization at different temperatures (400, 550, 700 and 850 °C) and thermal activation with CO2, has been investigated using N2 adsorption at −196 °C and CO2 adsorption at 0 °C. The effect of pre-oxidation of the carbonized precursor has also been studied, using temperature-programmed decomposition (TPD), to evaluate the
ABSTRACT MnOx–CeO2 and Pt(2%)/MnOx–CeO2 catalysts were prepared and investigated in the catalytic... more ABSTRACT MnOx–CeO2 and Pt(2%)/MnOx–CeO2 catalysts were prepared and investigated in the catalytic wet oxidation (CWO) of phenol. The reaction was carried out in a high-pressure autoclave reactor operating at 140 °C and oxygen partial pressure of 2 MPa. The effect of a reduction pre-treatment at 350 °C on the catalytic performance of both, the platinum catalyst and the bare oxide was studied. Higher activities were found for the reduced catalysts, independently of the presence or absence of Pt. Formation of carbonaceous deposits on the catalytic surface and leaching of manganese was confirmed as the two major deactivation mechanisms occurring in CWO of phenol. The amounts of deposits formed and manganese leached were higher in the case of reduced samples. Different techniques (XRD, HREM, HAADF, EDS, ICP) were used to characterise the chemical and structural changes experimented by the catalysts during reaction. The behaviour of reduced catalysts was found to be associated to the presence of MnO. The formation of this manganese oxide phase during the reduction pre-treatment significantly influenced the catalytic performance and stability of the catalysts under operation conditions.
Uploads
Papers by Mostafa Stitou