## 2 Results and Discussion  
### Adsorbent Synthesis and Characterization  
Copolymers chemically modified with pendant active groups containing nitrogen and/or oxygen were synthetized and characterized. The synthesis reaction is shown in Scheme 1. The functionalization reaction of the copolymers with aminobenzic acid. The evolution of the functionalization reactions was observed by FTIR spectroscopy. The FTIR spectrum (see Figure 1) shows the bands corresponding to the source S-15%DVB chloromethylated copolymer and respectively the absorption bands of the functionalized product PAB3. A decrease in the intensity of the \(\gamma\)CH\({}_{2}\)Cl band at 1260 cm\({}^{-1}\), was observed simultaneously with the appearance of the C=O carboxylic band from 1685-1695 cm\({}^{-1}\). The presence of COOH groups grafted on the copolymer was confirmed by the appearance of the C=O carboxylic band from 1748 cm\({}^{-1}\), assigned to the C=O stretching vibrations in aryl-COOH [36]. The presence of both COOH and NH groups on the PAB3 copolymer was confirmed by the intense broad band at 3424 cm\({}^{-1}\), which was attributed to the stretching vibration of both the OH and N-H groups. The spectrum showed an increase in the intensity of both the 1604 cm\({}^{-1}\) band and the 1120 cm\({}^{-1}\) band, which was attributed to the \(\delta\)NH and C-N stretching of aryl-NH-CH\({}_{2}\)- group [37]. The spectra of the products PAB1 and PAB2 are very similar due to the presence of the same type of copolymer matrix. The energy dispersive X-ray analysis (EDX) for the adsorbent PAB2 is presented in Figure 2.  
The data obtained from the X-ray energy dispersion, EDX, and analysis (see Table 1) of the three copolymer products functionalized with the aminobenzoic groups PAB1 (styrene--6.7%DVB), PAB2 (styrene--10%DVB), and PAB3 (styrene--15%DVB), confirmed the functionalization by the presence and content of nitrogen (PAB1: N% = 0.47; PAB2: N% = 0.85; PAB3: N% = 1.30) and oxygen (PAB1: O% = 7.61; PAB2: O% = 3.1; PAB3: O% = 10.95). \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Sample**} & \multicolumn{4}{c}{**wt \%**} \\ \cline{2-5}  & **C** & **N** & **O** & **Cl** \\ \hline PAB1 & 90.64 & 0.47 & 7.61 & 1.28 \\ PAB2 & 91.40 & 0.85 & 3.10 & 1.43 \\ PAB3 & 86.22 & 1.30 & 10.95 & 1.53 \\ \hline \end{tabular}
\end{table} 
Table 1: X-ray energy dispersion, EDX, quantification of the PAB1, PAB2, and PAB3 samples. Figure 1: FTIR spectra of the source copolymer and functionalized copolymer PAB3. In the scanning electron microscopy (SEM) image of the PAB3 sample (see Figure 3), the macropores are visible among the agglomerations of the microspheres; the sample is characterized by a dense structure. Thus, the PAB3 sample can be considered a macroporous material, which consists of agglomerations of microspheres, between which a porous structure with a labyrinth of channels can be observed. The thermal stability of the macromolecular adsorbents was studied by TG and DTA analysis. Thermograms of the PAB3 adsorbent are presented in Figure 4.  
The thermal behavior of the PAB3 sample in an atmosphere of nitrogen (Figure 4a) showed that weight loss began from 25 \({}^{\circ}\)C, which was due to the evaporation of physically adsorbed water or residual solvent (ethanol) in the adsorbent. Further, from \(\sim\)150 \({}^{\circ}\)C, the PAB3 sample started to decompose. Weight loss was observed in the temperature domain of 300-450 \({}^{\circ}\)C due to the decomposition of the C-C, C-N, and C-O bonds of the pendant active groups of the aminobenzoic type. The process of the decomposition of the pendant groups took place at a high speed, at 396 \({}^{\circ}\)C and 450 \({}^{\circ}\)C. The DTA suggest that the compound underwent thermal and oxidative decomposition both in nitrogen and in air (Figure 4a). After the temperature range of \(\sim\)400 \({}^{\circ}\)C to 600 \({}^{\circ}\)C, another decomposition process occurred; this was mainly due to the degradation of the copolymer chains, and  
Figure 3: SEM image of PAB3 sample.