## 3 Results and Discussion  
### Characterization of the Tested Adsorbents  
N\({}_{2}\) adsorption-desorption isotherms obtained at 77 K of f-CNT, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) particles and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT beads are depicted in Figure 1. The textural parameters, specific surface area (S\({}_{\mathrm{BET}}\)), external surface area (S\({}_{\mathrm{ext}}\)), pore volume (V\({}_{\mathrm{total}}\)) and pore diameter of the tested materials are collected in Table 1. According to IUPAC classification [35], carbon nanotubes (f-CNT) are materials that show a mainly mesoporous structure; with a contribution of microporous (-40 cm\({}^{3}\) g\({}^{-1}\) at low P/P\({}^{0}\) values) and an important quantity of meso-macroopores (type IVa isotherm, according IUPAC classification). These adsorbents show that both brands of N\({}_{2}\) adsorption isotherm are parallel and near to the verticality, characteristic of materials with cylindrical pores, where capillary condensation occurs (Table 1). Nevertheless, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT beads showed N\({}_{2}\) adsorption isotherms where, at low relative pressure values, the amount of N\({}_{2}\) adsorbed is very low (lower than 10 cm\({}^{3}\) g\({}^{-1}\)\({}_{\mathrm{STP}}\)). These are isotherms representative of essentially mesoporous material, without poor contribution of microporous on their structure. Thus, f-CNT material showed a low-moderate specific surface area (265 m\({}^{2}\) g\({}^{-1}\)), since relatively low BET area values were found for \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) nanoparticles and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT composites, 35 and 59 m\({}^{2}\) g\({}^{-1}\), respectively. Figure 1: N\({}_{2}\) adsorption-desorption isotherms at 77 K of f-CNT, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) particles and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT beads. The FTIR spectra of (A), f-CNT, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) nanoparticles, A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT beads are shown in Figure 2a. A wide band at 3400-3441 cm\({}^{-1}\) was observed in all spectra and attributed to the stretching vibration of -OH groups coming from the physically adsorbed water. The peak observed at 2923 cm\({}^{-1}\) for A, A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT spectra is due to the antisymmetric stretching vibration of the C-H groups. The absorption band in the range from 1625 to 1616 cm\({}^{-1}\) found in A, \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\), A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT materials was attributed to the symmetric vibrations of the COO\({}^{-}\) groups. The peaks at 1596 cm\({}^{-1}\) (\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)), 1415 cm\({}^{-1}\) (A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)) and 1421 cm\({}^{-1}\) (A, A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT) were due to the antisymmetric vibrations of COO\({}^{-}\) groups [36]. The stretching vibration of C-O groups in the alginate polysaccharide was confirmed at 1052 cm\({}^{-1}\), 1026 cm\({}^{-1}\) and 1020 cm\({}^{-1}\) for A, A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT, respectively. Finally the characteristic Fe-O elongation vibration was observed at 622 cm\({}^{-1}\) in \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) spectra and at 618 in A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT [37; 38]. The XRD patterns of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\), f-CNT and A/\(\gamma\)-Fe\({}_{2}\)O\({}_{3}\)/f-CNT materials can be seen in Figure 2b. The diffractograms obtained have broad diffraction lines, due to the nanometric size of \(\gamma\)-Fe\({}_{2}\)O\({}_{3}\) and f-CNTs materials.