## 3 Results and Discussion
### Developed Technologies for Exhausted Adsorbent and Desorption Solution Disposal
#### 3.5.3 Stabilization of Exhausted EGS@APTES-GT Material in UPe-Based Composites  
In the literature, studies on the development of adsorbents mostly focus on the development of the high removal capacity and on the regeneration of adsorbents without discussing the final disposal or stabilization of the effluent water or exhausted materials [33]. In order to solve the problem of the generated exhausted adsorbent in this study, the disposal of the spent adsorbent _ex_EGS, obtained after five cycles of adsorption-desorption processes, was solved by its use as a reinforcement in UPe-based composites. FTIR Analysis of UPe-Based Composites  
Figure 9 shows the FTIR spectra of the cured neat UPe matrix (a) and composites based on UPe reinforced with grinded _ex_EGS (UPe/_ex_EGS) at 2.5 wt.% (b), 5.0 wt.% (c), 7.5 wt.% (d), and 10 wt.% (e) additions. The bands observed at 2920 and 2850 cm\({}^{-1}\) for UPe and its derived composites were attributed to asymmetric and symmetric C-H stretching vibrations, and ones in the 1457-1370 cm\({}^{-1}\) region were assigned to the C-H bending vibrations of aliphatic moieties. The C=O stretching vibration of the ester carbonyl group was observed at 1715 cm\({}^{-1}\)  
Figure 9: FTIR spectra of cured UPe resin and UPe-based composites reinforced with exEGS at 2.5 wt.%, 5.0 wt.%, 7.5 wt.%, and 10 wt.% additions. The two peaks' small intensities at 1600 and 1576 cm\({}^{-1}\) were attributed to unsaturated C=C bonds in the phenyl ring of the terephthalyl unit and polystyrene in UPE resin. The bands related to the C-O and C-O-C stretching vibration appeared in the 1246 and 1100-1017 cm\({}^{-1}\) regions, respectively [67]. Also, two strong bands, found in the regions from 874 to 698 cm\({}^{-1}\), were assigned to the C-H out-of-plane deformation vibration of the phenyl ring in the terephthalyl units and polystyrene structure. The intensity of most bands in UPe and its corresponding composites are of a similar intensity (Figure 9) with one exception: the appearance of a new band at 973 cm\({}^{-1}\) assigned to the Si-O stretching vibration in exEGS. Generally, the spectra exhibit similarities between the samples, and the band's intensity is slightly proportionally increasing with the percent of the increase in the exEGS filler. The statistical results, obtained by the use of principal component analysis, or PCA, are applied to obtain results which are easier for analysis. On the normalized spectra, PCA analysis was applied (Figure S9). The PCA analysis of the FTIR data has a large number of highly correlated variables and only the first few PCs can describe the spectral variables relating to the chemical components/functional groups in the spectra of samples. These variables have large eigenvalues showing a steep slope, while the others PCs are the contribution of noise and the forming plate in the Scree plot due to their small eigenvalues (Figure S10) [68; 69]. Accordingly, the clustering of the spectral range in the FTIR spectra were performed in two ranges to select a proper spectral range by removing highly correlated variables. In order to determine the principal component numbers (PCs), we created the scree plot (Figure S10a) and drew the spectra (Figure S10b) of each PC [68; 69]. The results presented in Figure S10 indicate that PC1 and PC2 are the valuable components, while others from PC3 to PC6 show very small bands i.e., small eigenvalues. The obtained results in Figure S11a, b indicate that PC1 and PC2 cover 91,84% and 7.06% of the total variance, respectively, for the spectral range of 4000-400 cm\({}^{-1}\). The similar results are obtained by PCA analysis in the 1800-400 cm\({}^{-1}\) spectral range, and this range of the loading plot (Figure S11c,d) shows that PC1 and PC2 cover 86.73% and 11.97%, respectively. The obtained result shows high data variance in the investigated spectral ranges with changes in the intensity of the peaks.