*3.4. Fourier-Transform Infrared Spectroscopy (FTIR)*

The FTIR analysis of AC at a carbonization temperature of 700 ◦C was analyzed using the FTIR spectrometer within the scale of 400–4000 cm−<sup>1</sup> . Figure 4a shows The sharp band around 3650 cm−<sup>1</sup> was observed and represents the alcohol groups of O-H stretching vibration [29]. The small band were appearing at 3135 cm−<sup>1</sup> and 2895 cm−<sup>1</sup> correspond to the alcohol groups of O-H stretching of weak and intramolecular bonded. The strong band was appearing at 1725 cm−<sup>1</sup> and was generally ascribed to aldehyde groups of C=O stretching vibration [30]. The strong peak at 1530 cm−<sup>1</sup> was appearing and represent the nitro compound of N-O stretching vibration. The medium band at 1325 cm−<sup>1</sup> was observed and related to alcohol groups of O-H bending alcohol. The strong peak at 1110 cm−<sup>1</sup> was ascribed to the aliphatic ether of C-O stretching vibration. The two strong bands at 885 and 695 cm−<sup>1</sup> appearing may be related to alkene groups of C=C bending vibration [29].

**Figure 4.** FTIR spectra of (**a**) AC-700◦C and (**b**) NAC-700◦C.

Figure 4b show the FTIR spectrum NAC-700 ◦C of the peak at 3260 cm−<sup>1</sup> was observed as a weak band and represents an alcohol group of O-H stretching vibration. The two small peaks around 3060 and 2825 cm−<sup>1</sup> were assigned to the aliphatic group CH, -CH2, and –CH<sup>3</sup> [29,31]. The band at 2630 cm-1 was observed and assigned to aldehyde groups of C-H stretching. The weak band appearing at 1700 cm−<sup>1</sup> was allotted to carbonyl groups of C=O [29,32]. The strong peaks at 1540 cm−<sup>1</sup> and attributed to the nitro compound group of N-O stretching vibrations. The weak band at 1325 cm−<sup>1</sup> was generally credited to the alcohol group of O-H bending vibration. The strong peak at 1110 cm−<sup>1</sup> was ascribed to the aliphatic ether of C-O stretching vibration. The band at 670 cm−<sup>1</sup> may be ascribed to alkene groups of C=C bending vibration [29].
