**3. Results and discussions**

### **3.1 Synthesis and characterization**

BEC-ED synthesis was performed after HEC hydrophobization (partial benzylation) to decrease the rate of crosslinking in bio-adsorbent. In addition, crosslinking was performed with ED to study the effect of graft grouping on the ability to remove heavy metals from aquatic environments. The originality of this work is summed up in the fact that this type of product has never been described previously in the literature. The reaction scheme for the synthesis of BEC-ED, as a novel heavy metal adsorbent in aquatic media, is shown in **Figure 1**. The

**Figure 1.** *Reaction scheme of the preparation of BEC-ED.*

*New Ethylenediamine Crosslinked 2D-Cellulose Adsorbent for Nanoencapsulation Removal… DOI: http://dx.doi.org/10.5772/intechopen.98709*

crosslinking of BEC is carried out through the chlorination of the free OH groups, as an intermediate step, and then crosslinked by the ED in the THF using Triethylamine as the capturing agent of the released HCl to avoid the degradation of the cellulose chain under the effect of acid. However, the apparition of the white powder during the reaction indicating that the reaction of the crosslinking has been carried out successfully.

### *3.1.1 Structural analysis (FTIR)*

FTIR spectra of HEC, BEC, BEC-Cl, and BEC-ED are given in **Figure 2**. The FTIR of unmodified HEC spectrum showed infrared absorption bands spotted at 1062, 1408, 1458, 2873, 2927, and 3412 cm<sup>1</sup> . The absorption band at 3412 cm<sup>1</sup> is attributed to O–H stretching vibration [65], and a medium absorption band located in the range of 2927 and 2873 cm<sup>1</sup> corresponds to the C–H stretching vibration [66]. Moreover, the characteristic bands situated around 1408 and 1458 cm<sup>1</sup> are attributed to C–H symmetric bending vibration in –CHOH and O–H plane deformation of a primary alcohol, respectively [55]. The absorption band of b-(1,4)

**Figure 2.** *The FTIR spectra of HEC, BEC, BEC-Cl and BEC-ED.*

glycoside linkage was observed at 887 cm<sup>1</sup> [67], and that of C–O–C stretching vibration in the glucopyranose at 1062 cm<sup>1</sup> [68]. The absorption band at 1120 cm<sup>1</sup> corresponds to the C–O asymmetric vibration [67]. It can be seen, in **Figure 2**, that the modification of HEC by the benzyl group is apparent with a decrease in the intensity of the peak at 3347 cm<sup>1</sup> indicating a benzyl substitution of OH groups [69]. Indeed, the aromatic characteristic band elongations (=C–H) are situated between 3090 and 3033 cm<sup>1</sup> [70] and the aromatic C=Csp2 elongation vibrations are located at 1454 cm<sup>1</sup> [71]. In addition, the appearance of new absorption bands corresponding to the angular deformation (out of plane) of the monosubstituted aromatic C-H at around 740 cm<sup>1</sup> [72], and the C=C aromatic angular deformation, situated at 698 cm<sup>1</sup> , is a strong indication of the benzyl group incorporation on the HEC polymeric structure.

The comparison of FTIR spectra of unmodified BEC and chlorinated BEC (BEC-Cl) shows that the chlorination of BEC was carried out with success. Indeed, the new absorption band at 802 cm<sup>1</sup> , attributed to the stretching of the carbonchlorine bond C-Cl, is a strong indication that confirming the chlorination reaction. In addition, the decrease in band intensity at 3305 cm<sup>1</sup> is due to the substitution of the hydroxyl group by chlorine, which confirms the success of the reaction [73, 74]. After BEC crosslinking, the appearance of the characteristic –NH– absorption band between 3305 cm<sup>1</sup> and 3454 cm<sup>1</sup> designates the incorporation of amino entities into the BEC structure. The increase in the density of -CH2- groups in the cellulosic skeleton is noticed through the increase in the intensity of the absorption band corresponding to the stretching vibrations of the methylene (-CH2) groups at 2963 cm<sup>1</sup> . Furthermore, the ED crosslinking BEC is confirmed by the appearance of the different characteristic bands of the amino groups, which are located at 1095 cm<sup>1</sup> and 1590 cm<sup>1</sup> corresponding to the NH and CN stretching vibrations, respectively [75]. Thus, the intense peak attributed to the out-of-plane strain of NH at 802 cm<sup>1</sup> is very remarkable [75]. Also, the reduction in the intensity of the CO alcohol characteristic band around 1200 cm<sup>1</sup> is a strong indication of the substitution of OH by NH of ED [76–78].

## *3.1.2 Scanning electron microscopy, energy-dispersive x-ray (SEM-EDS) spectroscopy*

**Figure 3** shows SEM images of HEC, BEC, and BEC-ED. The resulted SEM images obtained for BEC showed homogenous, continuous, and microporous morphology, where pores diameter was estimated about (1–2) μm, which is radically different from the HEC aggregation aspect and lamellar BEC-ED morphologies. Yet, the morphological character of BEC allows it to be considered as a good candidate for microporous adsorbent/membranes applications. However, the EDS spectra of HEC and BEC showed a very significant increase in the C/O ratio, which indicates that the benzyl entities are grafted successfully. The evidence of BEC crosslinking by ED is shown by the EDS spectrum corresponding to BEC-ED, where the peak corresponding to nitrogen is very noticeable. In addition, BEC-ED SEM images showed a Nanoscale laminated appearance, including a lamellar structure that occurs through hydrophobic interactions. Based on BEC-ED morphology results, a supramolecular structure is proposed and schematically illustrated in **Figure 4**.
