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.

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 .…”

“…As mentioned in the first paragraph of this introduction, in Colombia, as in many Latin American countries, phenol is one of the compounds found in aquifer systems, generating major health problems for the entire population, especially the most unprotected, and mainly children. Several methods have been developed for the removal of phenol from water, such as photocatalytic degradation, electrochemical oxidation, solvent extraction, and biological degradation and adsorption, which is one of the most widely used methods for decontamination [4][5][6][7][8][9][10][11].…”

“…In Colombia, as well as in other countries in the area, coal distillation and organic synthesis waste flows bearing coal entities contain large amounts of phenols and their derivatives, as well as phenolic compounds, which are present in wastewater from pulp and paper-bleaching facilities, and from resin, pesticide, insecticide, paint, and solvent industries. That is why it is very important to face this problem and generate solutions that can be scaled to the most vulnerable populations; it is a social duty for academia [8,9].…”

“…According to the data, the process is favored in an activated carbon subjected to heat treatment at 1173 K, followed by treatment at 973 K, and finally at 1373 K. The author attributes this behavior to the increase in surface area caused by the increase in porous structures generated in the heat treatment; however, an excess of temperature leads to the collapse of the porous structure. When comparing the adsorption capacities of activated carbon without heat treatment and with treatment at 1173 K for different temperatures for the adsorption system (298 K, 313 K, 328 K), it was found that the adsorption capacity does not vary with temperature but the heat treatment for the sample favors the process (1.27 < 1.54 mmol g −1 ) [7][8][9][10][11].…”

Sorption of phenols on hexadecyltrimethylammonium- modified bentonite: Application of Polanyi−Manes potential theory

“…The Sips model is defined as: 35 where q mS is the maximum sorption capacity (mmol/g), b S (L/mmol) is Sips equilibrium constant, and N S (–) is the Sips model exponent. If N S = 1, the Sips model is equal to the Langmuir model.…”