immobilization on the carbonaceous surface, adsorptionheat is one of the fundamental parameters. To ascertain the values of the adsorption enthalpy, courses of adsorption isotherms measured at different temperatures are often analysed, so offering information on
Authors:Roman Bulánek, Karel Frolich, Eva Frýdová, and Pavel Čičmanec
represents a measure of the strength of these interactions. Therefore, adsorptionheats bring information about heterogeneity of the adsorption sites on the surface of the adsorbent. In addition, knowledge of the adsorptionheat is very important for the
Authors:H. Bahaj, M. Bakass, C. Bayane, J. P. Bellat, M. Benchanaa, and G. Bertrand
showed their efficiency as air dehumidifier [ 18 ]. An understanding of the process of adsorption of water vapor on solid surfaces requires knowledge of both the adsorbed amounts and the adsorptionheats. The heats of adsorption allow an assessment of the
Authors:Vratislav Tydlitát, Jan Zákoutský, and Robert Černý
of phase transition [ 3 ], enthalpy of combustion [ 4 ], adsorptionheat [ 5 ], enthalpy of formation [ 6 ], heat of salt hydration [ 7 ], solution enthalpy [ 8 ], and thermal conductivity [ 9 ] present only a few characteristic examples of parameters
Authors:E. Fiani, L. Perier-Camby, G. Thomas, and M. Sanalan
Adsorption isotherms of n-butane on a granulated activated carbon were measured by two different but complementary experimental
methods: calorimetry and gravimetry. Adsorption heats were determined in different ways. For the system studied, the experimental
results prove that the adsorbent offers a homogeneous site distribution. Besides, there can be differences between the adsorption
heat values which might come from the way they are obtained (by calculation or direct measurements).
The heats of hydration reactions for MgCl2⋅4H2O and MgCl2⋅2H2O include two parts, reaction enthalpy and adsorption heat of aqueous vapor on the surfaces of magnesium chloride hydrates.
The hydration heat for the reactions MgCl2⋅4H2O+2H2O→MgCl2⋅6H2O and MgCl2⋅2H2O+2H2O→MgCl2⋅4H2O, measured by DSC-111, is –30.36 and –133.94 kJ mol–1,respectively. The adsorption heat of these hydration processes, measured by head-on chromatography method, is –13.06 and
–16.11 kJ mol–1, respectively. The molar enthalpy change for the above two reactions is –16.64 and –118.09 kJ mol–1, respectively. The comparison between the experimental data and the theoretical values for these hydration processes indicates
that the results obtained in this study are quite reliable.
The adsorption heat of the stoichiometric displacement process for the adsorption of a solute in a liquid-solid system was
investigated. On the basis of the SDM-A and the rule of the additivity of energy, an expression which describes the dependence
of the adsorption enthalpy on the nature and concentration of the solute, and on the solvent and adsorbent, was derived. The
adsorption heat determined for the solute with the traditional method can be divided into two independent fractions, relating
to the adsorption of the solute and to the desorption of the solvent. Experimental data on both isotherms from the literatures
and precise calorimetry were used to test the adsorption heat and its fractions computed quantitatively via the equations
presented in this study, and a satisfactory degree of conformity between them was obtained.
The influence of microporous carbon surface oxidation on energetics of methane adsorption at 308 K is discussed. Obtained
adsorption heats and integral molar entropies of the adsorbate show that microporous carbon surface oxidation changes the
methane adsorption process. This is probably resulted by the existence of an endothermic effect during adsorption in oxidized
The role of calorimetry in adsorption is shortly reviewed. The differences between calorimetric adsorption heats and those
calculated from Clausius-Clapeyron equation for the systems ethanol-activated carbons are presented. Obtained results, together
with the results presented previously for other adsorbates, confirm that calorimetry is indispensable for a real thermodynamical
description of the adsorption process in this type of system.
Authors:V. García-Cuello, J. Moreno-Pirajan, L. Giraldo-Gutiérrez, K. Sapag, and G. Zgrablich
In this work, it is described an innovative heat flux micro calorimeter Tian-Calvet type designed to measure adsorption heats
and reactions as well as adsorption isotherms. It consists in an adsorption instrument for volumetric gases, which is coupled
to the micro calorimeter. The changes in the pressure are monitored by means of high sensitivity and high precision pressure
transducers. The micro calorimeter has thermo elements that work by a Seebeck effect, in a twin cells system. The cells are
inside a box in which the temperature can be adjusted from 77 to 300 K. The sensitiveness of the calorimeter is established
by applying a perfectly known electric work. The results corresponding to the electric calibration, the base line stability
determination and the time constant in the equipment are shown.