## 3 Results and Discussion
### Activated Carbons by Chemical Activation of Hydrochars
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & **C** & **Ash** & **A\({}_{\text{BET}}\)** & **A\({}_{\text{ext}}\)** & **V\({}_{\text{micro}}\)** & **V\({}_{\text{meso}}\)** \\  & **(wt.\% Dry Basis)** & **(wt.\% Dry Basis)** & **(m\({}^{2}\)g-1)** & **(m\({}^{2}\)g-1)** & **(cm\({}^{3}\)g-1)** & **(cm\({}^{3}\)g-g-1)** \\ \hline GSHC-KOH-2 & 75.1 & 9.8 & 1215 & 35 & 0.57 & 0.02 \\ GSHC-KOH-3 & 73.3 & 16.3 & 2194 & 121 & 0.98 & 0.05 \\ GSHC-KOH-4 & 45.6 & 38.2 & 1780 & 260 & 0.74 & 0.18 \\ \hline GSHC-FeCl\({}_{3}\)-2 & 51.1 & 44.4 & 394 & 44 & 0.17 & 0.02 \\ GSHC-FeCl\({}_{3}\)-3 & 49.7 & 46.0 & 417 & 54 & 0.17 & 0.02 \\ GSHC-FeCl\({}_{3}\)-4 & 35.7 & 49.2 & 312 & 50 & 0.12 & 0.02 \\ \hline GSHC-H\({}_{3}\)PO\({}_{4}\)-2 & 63.3 & 4.6 & 654 & 255 & 0.19 & 0.23 \\ GSHC-H\({}_{3}\)PO\({}_{4}\)-3 & 61.4 & 7.6 & 596 & 242 & 0.17 & 0.21 \\ GSHC-H\({}_{3}\)PO\({}_{4}\)-4 & 69.7 & 10.8 & 590 & 172 & 0.20 & 0.16 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Textural characteristics of the activated carbons. Figure 2: N\({}_{2}\) adsorption-desorption isotherms at 77 K of the activated carbons obtained at 3:1 activating agent to hydrochar ratio. Figure 4 shows the FTIR spectra of the raw GS, GS-220-40 hydrochloric and the activated carbons obtained with an activating agent to hydrochar ratio of 3. A decreasing intensity of the O-H stretching of the hydroxyl groups at 3400 cm\({}^{-1}\) was observed for the hydrochar, because the dehydration occurred upon HTC [56; 57]. The bands appearing in the 2950 to 2750 cm\({}^{-1}\) range, associated to aliphatic carbon \(-\)CH\({}_{\rm x}\) stretching vibration, tended to be less intense for the GS-220-40 hydrochar, probably due to the evolution of nonpolar alkyl carbon structure [58]. In addition, transmission intensities at 1750-750 cm\({}^{-1}\) arising from C=O stretching of ketones and other carbonyl structures were reduced. Furthermore, the decline of the peak at 1030 cm\({}^{-1}\) (the C-O and C-O-C stretching) indicates that both decarboxylation and dehydration occur, consistently with the van Krevelen representation of Figure 1.  
The FTIR spectra of activated carbons showed a dramatic decrease of functionalities in agreement with the reported in general in the literature relative to activation of carbon precursors. A broad band (3600-3100 cm\({}^{-1}\)) appears in the three activated carbons, related to the existence of hydroxyl functional groups. Those related to C=C and aromatic rings vibration (1600-1500 cm\({}^{-1}\)) and the associated to C-O bonds at 1157-1090 cm\({}^{-1}\), related to the presence of alcohol groups were more intense in the GSHC-FeCl\({}_{3}\)-3, and, mainly, in the GS-H\({}_{3}\)PO\({}_{4}\)-3 activated carbons [59; 60]. The amount of surface oxygen groups in the activated carbons was assessed in terms of CO\({}_{2}\) and CO evolved upon TPD. The results are summarized in the inside Table of Figure 4. In all the cases, the ratio CO\({}_{2}\)/CO was within 27-30%, suggesting that the oxygen groups must be ascribed majorly to CO-evolving functionalities (phenol, carbonyl, anhydride ether, quinone), mainly associated to weak acid and neutral/basic surfaces. However, there are also some significant amounts of evolved CO\({}_{2}\), such that carboxylic, lactone and anhydride groups may be also present in some extent [61; 62]. H\({}_{3}\)PO\({}_{4}\), and in particular, FeCl\({}_{3}\), appear to be more prone than KOH to create oxygen groups on the carbon surface upon activation. [PERSON] et al. [62] arrived to similar conclusion working with Fe(NO\({}_{3}\))\({}_{3}\) as a precursor. Figure 3: SEM images of cross-section of GS (**a**), GS-220-40 hydrochar (**b**), and GSAC-KOH-3 (**c**), GSAC-FeCl\({}_{3}\)-3 (**d**) and GSAC-H\({}_{3}\)PO\({}_{4}\)-3 (**e**) activated carbons.