## 3 Results and Discussion
### Adsorption of Phenol at Equilibrium  
For comparative purposes, Figure 6 shows the isotherms obtained in the phenol adsorption process on activated carbons at 291 K until equilibrium is reached. These isotherms were also studied with regard to the Langmuir and modified Langmuir models. Figure 5: pH values for the phenol adsorption process during the two hours of the calorimetric determination. The lines correspond to the tendency of the dates. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Samples** & \begin{tabular}{c} **Total Aidity** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Total Basicity** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Carboxylic Groups** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Lactonic Groups** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} **Phenolic Groups** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} **pH\({}_{\text{PZC}}\)** \\ **(\(\mu\)mol g\({}^{-1}\))** \\ \end{tabular} \\ \hline G & 90.5 & 742 & 22.2 & 21.8 & 46.6 & 7.48 \\ GN & 6560 & 735 & 106 & 489.5 & 59.9 & 3.13 \\ GNA & 377 & 799 & 63.2 & 289 & 24.6 & 7.41 \\ GP & 423 & 849 & 109 & 137 & 177 & 5.91 \\ GC\({}_{1073}\) & 93.6 & 1210 & 66.1 & 21.2 & 6.36 & 7.65 \\ GC\({}_{1173}\) & 93.0 & 1630 & 65.5 & 23.8 & 3.71 & 7.89 \\ GC\({}_{1273}\) & 94.1 & 2040 & 64.7 & 46.8 & 17.5 & 9.97 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical parameters of the activated carbons. Figure 6 shows the changes in the interaction between phenol and activated carbon at equilibrium due to contact time. In this case, the adsorption increased compared to the adsorption that occurs in the calorimetric immersion process. The parameters obtained for the adsorption of phenol data in the equilibrium at 291 K are summarized in Table 4.  
The main difference between these two groups of activated carbons is that the first corresponds to those samples that were carbonised and the original activated carbon. These samples have a greater portion of graphene surface due to the carbonisation process. The second group corresponds to the activated carbons that were impregnated, and which therefore contain more oxygenated groups on the surface. These results indicate that the initial adsorption is specific between the phenol and the groups on the surface, while the non-specific interactions between the hydrophobic sites in the solute and the surface of the activated carbons require more time, because they are mainly \(\pi\)-\(\pi\) interactions [7]. According to [PERSON], the hydrophobic links are entropic process-driven, and are the result of a loss of water around the non-polar sites of adsorbate molecules, while specific adsorption is an enthalpy-driven process [3; 22]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Modified Model of Langmuir**} & \multicolumn{4}{c}{**Langmuir Model**} \\ \hline
**Samples** & **K1** & **K2** & **KHB** & **R** & **Qo** & **KL** & **R** \\ \hline  & **L-mmol-1** & **mmol-g-1** & **mmol-g-1** & & **mmol-g-1** & **L-mmol-1** & \\ \hline G & 5.03 & 1.51 & 0.074 & 0.995 & 1.57 & 6.01 & 0.990 \\ GN & 370. & 0.73 & 0.155 & 0.964 & 0.76 & 464 & 0.954 \\ GNA & 19.5 & 0.89 & 0.151 & 0.967 & 0.90 & 152 & 0.939 \\ GP & 8.12 & 1.07 & 0.034 & 0.976 & 1.06 & 8.78 & 0.975 \\ GC1073 & 3.65 & 1.67 & 0.129 & 0.981 & 1.67 & 6.50 & 0.977 \\ GC1173 & 11.9 & 1.58 & 0.097 & 0.982 & 1.73 & 13.8 & 0.978 \\ GC1273 & 5.08 & 1.41 & 0.131 & 0.987 & 1.35 & 11.5 & 0.961 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Adjustment parameters to the Langmuir and Langmuir modified models for the adsorption of phenol from aqueous solution in equilibrium. Figure 6: The phenol adsorption isotherms on activated carbons at 291 K. The lines correspond to the adjustment of adsorption data for the modified model of Langmuir.