In this study, the amount of phenol adsorbed between 0 and 10 mmol·L −1 during an immersion calorimetric experiment is compared with the adsorption that takes place once phenol adsorption reaches the solid-solution equilibrium. The activated carbons used were prepared by impregnation of one obtained from coconut shell with solutions of nitric and phosphoric acid, nitric acid with subsequent reflux in ammonium hydroxide solution, and carbonisation in a nitrogen atmosphere at 1073, 1173, and 1273 K. The phenol/activated carbon interactions during the calorimetric experiment and in equilibrium were studied using a modified Langmuir model. The values of the BET surface area for the samples were between 469 and 1113 m 2 ·g −1 , micropore volumes were between 0.18 and 0.43 cm 3 ·g −1 , and the distribution of pore size was between 0.3 and 1.4 nm. The interactions between water and activated carbons determined by immersion enthalpies were between −11.0 and −24.8 J·g −1 , which showed that the treatments modified the surface chemistry of activated carbon. The results show that the presence of nitrogen as a different heteroatom to oxygen on the activated carbon surface favors the phenol adsorption rate, and this process is 97% complete during the calorimetric experiment, indicating that it is an enthalphy-driven processes.

In this study, the microstructure of a series of activated carbons modified on its chemistry surface was evaluated from X-ray diffraction and porous structure analysis, and the effect of the stacked graphitic structure on the n-pentane adsorption capacity. The activated carbons were prepared modifying an activated carbon (obtained from coconut shell) by carbonization processes at 1073, 1173 and 1273 K and impregnation with 65% nitric acid solution, 60% phosphoric acid solution and reflux with 30% ammonium hydroxide solution. The activated carbons were characterized by N2 adsorption at 77 K. It was found that these are essentially microporous materials with surface areas between 469 and 1113 m2 g-1, and the evaluation of the microstructure was performed by determining the number of aromatic layers stacked from the analysis of the observed diffraction peak between 20-30° 2θ which corresponds to the 002 reflection in the plane of the coal using the STACK XRD technical. The results showed that impregnation as carbonization favours the development of the crystalline structure to the activated carbons, which is shown by the increase of the stacked structure at the same time; this favours the n-pentane adsorption.

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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.

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