Application of the Sips model to the calculation of maximum adsorption capacity and immersion enthalpy of phenol aqueous solutions on activated carbons

Abstract

The Sips model for heterogeneous systems was used to describe the immersion enthalpy, maximum adsorption capacity at three temperatures, namely, 283, 291 and 308 K; and interactions between phenol aqueous solutions and activated carbon modified on its surfaces by impregnation with 6.0 M HNO3 and 3.0 M H3PO4 solutions. Activated carbon properties, such as porosity, Brunauer-Emmett-Teller (BET) surface area and volume and size pore distributions, were determined using N2 adsorption at 77 K. Surface area values were calculated to be between 469 and 864 m 2 /g. Also, the pH at the point of zero charge, acidity and total basicity for the activated carbons were obtained. The result showed that the Sips model in addition to describe the phenol concentration in equilibrium can be used to study immersion enthalpy when 1/ns is equal to 1.

Efficient Uptake of Angiotensin-Converting Enzyme II Inhibitor Employing Graphene Oxide-Based Magnetic Nanoadsorbents

“…Additionally, the maximum adsorption capacity estimated by this model decreased with the rise in the temperature, indicating that adsorption is an exothermic process (in agreement with the thermodynamic study) [45]. On the other hand, in the Sips constant related to equilibrium (Ks), a considerable decrease was observed with the gradual increase in temperature, i.e., suggesting that the process is disadvantaged at high temperatures [53].…”

Physicochemical Characterization of Santa Barbara Amorphous-15 (SBA-15) and Its Functionalization with Polyaniline for Phenol Adsorption

“…On the other hand, other authors have reported [8] that the isosteric heat of adsorption decreased when the concentration increased from −78 kJ mol −1 to −5.5 kJ mol −1 ; likewise, the immersion enthalpies showed the same trend and varied between −2152 and 82.8 J g −1 .…”

Characterization of CO2 Adsorption Behavior in Pyrolyzed Shales for Enhanced Sequestration Applications

“…The Sips isotherm model is an empirical three-parameter model also known as a hybrid isotherm of the Langmuir and the Freundlich models [ 67 ]. This isotherm model is presented to better predict the heterogeneity of the sorption surfaces and to overcome the inadequacies of the Freundlich isotherm’s increasing sorbate concentration [ 68 ]. It tends toward the Freundlich isotherm when the concentration of the sorbate is low and tends to predict the Langmuir isotherm when the concentration is high, forming a monolayer sorption phenomenon [ 69 ].…”