## 3 Results and Discussion
### Characterization of the Tested Adsorbents
For \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\), the peaks corresponding to the planes (111), (220), (311), (400), (511), (440) and (533) were observed at 20 = 17.85\({}^{\circ}\), 30.16\({}^{\circ}\), 35.90\({}^{\circ}\), 43.83\({}^{\circ}\), 57.57\({}^{\circ}\), 63.24\({}^{\circ}\) and 76.57\({}^{\circ}\), respectively. The corresponding interplanar distance at 20 = 43.83\({}^{\circ}\) is of d (400) = 0.2085 nm, that is very close to that reported in the literature [39; 40]. The diffractogram fitted very well to the cubic symmetry of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) with the P4\({}_{1}\)32 space group. The Rietveld analysis by the MAUD software confirmed the good crystallinity of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) with a cubic elementary mesh (a = 0.8341 nm). This value is in agreement with that reported in the literature for the same nanoparticles [41]. The average value of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) crystals \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **S\({}_{\text{SET}}\) (m\({}^{2}\) g\({}^{-1}\))** & **S\({}_{\text{ext}}\) (m\({}^{2}\) g\({}^{-1}\))** & **V\({}_{\text{Total}}\) (cm\({}^{3}\) g\({}^{-1}\))** & **Pore Diameter (nm)** \\ \hline
**f-CNT** & 265 & 331 & 1.35 & 2.5–3.5 \({}^{\text{a}}\) \\
**\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)** & 35 & 31 & 0.06 & 1.0–1.6 \({}^{\text{b}}\) \\
**A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT** & 59 & 103 & 0.14 & 1.0–1.5 \({}^{\text{b}}\) \\ \hline \hline \end{tabular} \({}^{\text{a}}\) Estimated by BjH model; \({}^{\text{b}}\) Estimated by MP method.  
\end{table} 
Table 1: Textural parameters of f-CNT, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT beads. obtained by the refinement was of 10.59 nm, whereas the size calculated by Scherrer equation was of 10.24 nm. This value is in agreement with that obtained by [PERSON] et al. [42], where resulted in 10 nm. By comparison between the f-CNT diffractogram used in this study and that of the non-functionalized CNT reported in the literature [38], it could be concluded that the functionalization of CNTs with acid does not alter the crystallographic character of the material; only two peaks at 20 = 25.47\({}^{\circ}\) (002) and 20 = 42.81\({}^{\circ}\) (100) corresponding to the interplanar distances of 0.35 and 0.211 nm, respectively, were observed. The presence of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) in A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT was confirmed by the presence of the peaks attributed to the planes (220), (311), (400), (511) and (440) related to the interplanar distances of 0.294, 0.251, 0.209, 0.159 and 0.147 nm, respectively. The characteristic peaks of f-CNT were not identified in the patterns of composite material (A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT) due to the low initial f-CNT weight ratio used in the preparation of alginate beads (0.4%). In addition, the presence of the peak at 20 = 43.83\({}^{\circ}\) (400) in maghemite XRD pattern caused the disappearance of the characteristic peak of f-CNT at 20 = 42.81\({}^{\circ}\) (100). These findings may be also attributed by the presence of alginate in the material, which reduces the purity of f-CNT in the final composite. It should be noted that A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT have the same characteristic peaks that \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) have, indicating that the presence of alginate and f-CNTs in the composite did not alter the crystallographic character of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\). The thermal stability of the materials was evaluated by thermogravimetric analysis. Figure 3a-e show the TGA/TDG curves of the different samples accomplished in a temperature range of 30 to 900\({}^{\circ}\) C. The alginate curve showed an initial weight loss of 12.77 % between 30 and 200 \({}^{\circ}\)C corresponding to the loss of water. At temperature between 200 and 500 \({}^{\circ}\)C, the glycosidic bonds were destroyed which corresponds to a weight loss of 47.76 % [43]. The third loss of mass (16.71%) could be attributed to the formation of CaCO\({}_{3}\)[44].