## 3 Results and Discussion
### Textural and Chemical Characterization of the Adsorbents
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Sample** & **S\({}_{\text{BET}}\) (m\({}^{2}\)/g)** & \begin{tabular}{c} **S\({}_{\text{mi}}\)\({}^{\alpha}\)** \\ **(m\({}^{2}\)/g)** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{t}}\)\({}^{\beta}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{me}}\)\({}^{\alpha}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{mi}}\)\({}^{\alpha}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{ultra}}\)\({}^{\alpha}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} & \begin{tabular}{c} **S\({}_{\text{ini}}\)/S\({}_{\text{BET}}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} & \
\begin{tabular}{c} **V\({}_{\text{ini}}\)/V\({}_{\text{t}}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} &
\begin{tabular}{c} **V\({}_{\text{ultra}}\)/V\({}_{\text{t}}\)** \\ **(cm\({}^{2}\)/g)** \\ \end{tabular} \\ \hline ACF & \(966\pm 16\) & 862 & 0.4635 & 0.0427 & 0.3472 & 0.1456 & 0.892 & 0.749 & 0.314 \\ aACF & \(1565\pm 26\) & 1224 & 0.7357 & 0.1135 & 0.5028 & 0.2020 & 0.782 & 0.683 & 0.275 \\ nACF & \(797\pm 10\) & 599 & 0.3848 & 0.0612 & 0.2610 & 0.0923 & 0.752 & 0.678 & 0.240 \\ \hline \hline \end{tabular} \({}^{\alpha}\) Microporne area, micropore volume, ultramicropore volume, and mesopore volume were determined by the density functional theory (DFT) method, where an ultramicropore was defined as a pore size less than 0.7 nm. \({}^{\beta}\) Total pore volume (V\({}_{\text{t}}\)) represented the single point total pore volume at P/P\({}_{\text{o}}\approx\) 0.99.  
\end{table} 
Table 1: Textural properties of the samples determined from the adsorption-desorption isotherms of N\({}_{\text{2}}\) at \(-196\)\({}^{\circ}\)C.  
Figure 1: Pore size distributions of the activated carbon fiber samples obtained from the DFT method, where: inset (**a**) micropore range; inset (**b**) ultramicropore range. potassium-based compounds with ACFs were responsible for the change in the morphology of the ACFs [27]. On the other hand, the TPEA modification of ACFs did not cause any perceptible variation in the filament appearance (Figure 2c). Previous studies have shown that CO\({}_{2}\) adsorption capacities are closely linked to surface heteroatomic species of the adsorbents, especially to N-functionalities [11; 19; 29]. Accordingly, XPS was conducted to examine the surface chemical states. As seen from Figure 3a, the primary characteristic peaks in the survey scan spectra of the adsorbents are due to the photoelectrons of C\({}_{18}\), O\({}_{18}\), and N\({}_{18}\). The KOH activation of ACF resulted in a significant loss of nitrogen atoms during activation (Figure 3b), consistent with findings from [PERSON] et al. [10]. The surface of ACF consisted of 8.2 at% of O\({}_{18}\) and 2.4 at% of N\({}_{18}\), where the nitrogen originated from its PAN precursor (Figure 3b). The nitrogen content on nACF was not significantly increased, which could be ascribed to it undergoing a heat treatment at 500 \({}^{\circ}\)C after immersion. Nevertheless, the results confirmed that the surface of ACF has been decorated with nitrogen-based groups from TPEA. Figure 3c-d show a comparison of the N\({}_{18}\) and O\({}_{18}\) regions for the adsorbents. It is evident that the major groups of N-and O-functionalities have transformed to others after modifications. In order to understand the chemical bonding states, deconvolution of high-resolution XPS O\({}_{18}\), and N\({}_{18}\) peaks of the adsorbents was carried out. Deconvolution of the O\({}_{18}\) region provided information on the distribution of the surface oxygen-functionalities. The optimal results were used to calculate the values of the atomic percent of oxygen-functionalities after curve fitting of the O\({}_{18}\) region for the samples (Figure 4a).