**3. Results and discussion**

### **3.1 Chemical analysis**

The chemical analysis of LDH samples is shown in **Table 1**. The molar ratio of *<sup>M</sup> II*∕*<sup>M</sup> III* in L1 or L4 is nearly 2 which is well fitted to the expected formula. However, L2, L3, or L5 has lower *<sup>M</sup> II*∕*<sup>M</sup> III* ratio than L1 or L4. The presence of polydentate ligand (Zn-EDTA or Al-EDTA complex) can result in this decrease of the ratio. Moreover, the decrease suggests that octahedron in hydroxyl layer has a partial dissolution (p*K*sp (Zn(OH)2) = 13.7, p*K*sp (Al(OH)3) = 32.7, p*K*sp (Mg(OH)2) = 12.7) during the anion exchange reaction which is performed at pH 5–6 [12, 17, 26]. The C/N of L5 is lower than that of EDTA ligand (5), and the little gap between them may be mainly due to the registration of nitrate ions in the interlayer. The more nitrate ions are included in LDHs, the lower the C/N value is [27].

#### **3.2 FT-IR spectra**

The FT-IR spectra of L1 and L2 and L3 are shown in **Figure 3**, and that of L4 and L5 are shown in **Figure 4**. Typical M-OH (M—metallic ions) vibration modes due to the hydroxide layer between 400 and 1000 cm<sup>−</sup><sup>1</sup> are found in both **Figures 3** and **4**.

The very sharp peak at 1385 cm<sup>−</sup><sup>1</sup> in **Figures 3(a)** and **4(a)** is attributed to the NO3 − stretching vibration. The NO3 − stretching vibration at 1385 cm<sup>−</sup><sup>1</sup> is not observed from **Figures 3(b)** to **4(b)**. It may be due to the group which is hidden by the band at 1394 cm<sup>−</sup><sup>1</sup> [26, 28]. The absorption bands at 1600 and 1394 cm<sup>−</sup><sup>1</sup> are characteristics of the symmetrical and asymmetrical vibration of COO- groups. The position of these bonds is similar to the spectrum of LDHs which is reported by Parida et al. [29] and [30]. It is found that EDTA has been intercalated into the interlayer successfully, although a certain amount of -NO3 may still retain in the compound judging from the results of chemical analysis. The wide band at around 3450 cm<sup>−</sup><sup>1</sup> may be attributed to the -H bonding stretching vibrations of -OH groups and water molecules. The band at 1623 cm<sup>−</sup><sup>1</sup> of L1 and L4 is assigned to water bending vibration [8, 26].

#### **3.3 XRD patterns**

XRD patterns of L1 and L2 and L3 are shown in **Figure 5**, and those of L4 and L5 are shown in **Figure 6**. They are typical XRD patterns of LDHs. The strong diffraction peaks at low angle, assigned to basal planes (003), (006), (009), were sharp and symmetric compared to the peaks at high angle, which are characteristics of clay mineral


**171**

complexes (0.9 nm<sup>−</sup><sup>1</sup>

**Figure 3.**

**Figure 4.**

*FT-IR spectra of (a) L1, (b) L2, and (c) L3.*

**3.4 SEM micrographs**

ions) compound [12, 17, 30, 32].

*FT-IR spectra of (a) L4 and (b) L5.*

*Adsorption of Heavy Metals on Layered Double Hydroxides (LDHs) Intercalated with Chelating…*

shaving a layered structure [29–31]. From the XRD pattern, the basal spacing (d) values of sample were calculated by using Bragg equation and the angle of peak (003). Then the gallery height was obtained by subtraction from the basal spacing to the layer width (0.48 nm) [30]. The basal spacing and the gallery height of L1, L2, L4, and L5 are shown in **Table 2**. It indicates that the intercalation of EDTA into NO3-LDHs gives rise to an increase of basal spacing. This basal spacing could identify the existence of EDTA, because it is close to the dimensions of EDTA

SEM images of all composite synthesized in this work are shown in **Figure 7**. These adsorbents have clear plate-like morphology, which is typical for LDHs [33]. The intercalated product particles are more homogeneous than the precursor product

nm) founded by single crystal XRD of M-EDTA (M—metallic

*DOI: http://dx.doi.org/10.5772/intechopen.80865*

#### **Table 1.**

*Chemical analysis results of L1, L2, L3, L4, and L5.*

*Adsorption of Heavy Metals on Layered Double Hydroxides (LDHs) Intercalated with Chelating… DOI: http://dx.doi.org/10.5772/intechopen.80865*

#### **Figure 3.**

*Advanced Sorption Process Applications*

in LDHs, the lower the C/N value is [27].

The very sharp peak at 1385 cm<sup>−</sup><sup>1</sup>

stretching vibration. The NO3

the hydroxide layer between 400 and 1000 cm<sup>−</sup><sup>1</sup>

The chemical analysis of LDH samples is shown in **Table 1**. The molar ratio of *<sup>M</sup> II*∕*<sup>M</sup> III* in L1 or L4 is nearly 2 which is well fitted to the expected formula. However, L2, L3, or L5 has lower *<sup>M</sup> II*∕*<sup>M</sup> III* ratio than L1 or L4. The presence of polydentate ligand (Zn-EDTA or Al-EDTA complex) can result in this decrease of the ratio. Moreover, the decrease suggests that octahedron in hydroxyl layer has a partial dissolution (p*K*sp (Zn(OH)2) = 13.7, p*K*sp (Al(OH)3) = 32.7, p*K*sp (Mg(OH)2) = 12.7) during the anion exchange reaction which is performed at pH 5–6 [12, 17, 26]. The C/N of L5 is lower than that of EDTA ligand (5), and the little gap between them may be mainly due to the registration of nitrate ions in the interlayer. The more nitrate ions are included

The FT-IR spectra of L1 and L2 and L3 are shown in **Figure 3**, and that of L4 and L5 are shown in **Figure 4**. Typical M-OH (M—metallic ions) vibration modes due to

from **Figures 3(b)** to **4(b)**. It may be due to the group which is hidden by the band at

the -H bonding stretching vibrations of -OH groups and water molecules. The band at

XRD patterns of L1 and L2 and L3 are shown in **Figure 5**, and those of L4 and L5 are shown in **Figure 6**. They are typical XRD patterns of LDHs. The strong diffraction peaks at low angle, assigned to basal planes (003), (006), (009), were sharp and symmetric compared to the peaks at high angle, which are characteristics of clay mineral

**wt% N H Atomic ratios Proposed formula**

L1 0.54 5.17 3.24 2.23 0.01 8.79 [Mg2Al(OH)6]NO3 L2 11.2 3.83 4.19 1.88 0.22 20.1 [Mg2Al(OH)6]2[C10H14N208] L3 9.82 2.21 4.15 1.79 0.20 26.3 [Mg2Al(OH)6]2[C10H13N2Na08] L4 0.06 4.26 2.38 2.10 0.00 7.82 [Zn2Al(OH)6]NO3 L5 13.7 3.35 3.60 1.67 0.31 15.1 [Zn2Al(OH)6]2 [C10H14N208]

**C/H H/N**

of L1 and L4 is assigned to water bending vibration [8, 26].

of the symmetrical and asymmetrical vibration of COO- groups. The position of these bonds is similar to the spectrum of LDHs which is reported by Parida et al. [29] and [30]. It is found that EDTA has been intercalated into the interlayer successfully, although a certain amount of -NO3 may still retain in the compound judging from the

−

[26, 28]. The absorption bands at 1600 and 1394 cm<sup>−</sup><sup>1</sup>

results of chemical analysis. The wide band at around 3450 cm<sup>−</sup><sup>1</sup>

**C MII/**

*Chemical analysis results of L1, L2, L3, L4, and L5.*

**MII**

are found in both **Figures 3** and **4**.

is not observed

are characteristics

may be attributed to

in **Figures 3(a)** and **4(a)** is attributed to the

stretching vibration at 1385 cm<sup>−</sup><sup>1</sup>

**3. Results and discussion**

**3.1 Chemical analysis**

**3.2 FT-IR spectra**

NO3 −

1394 cm<sup>−</sup><sup>1</sup>

1623 cm<sup>−</sup><sup>1</sup>

**3.3 XRD patterns**

**170**

**Table 1.**

*FT-IR spectra of (a) L1, (b) L2, and (c) L3.*

**Figure 4.** *FT-IR spectra of (a) L4 and (b) L5.*

shaving a layered structure [29–31]. From the XRD pattern, the basal spacing (d) values of sample were calculated by using Bragg equation and the angle of peak (003).

Then the gallery height was obtained by subtraction from the basal spacing to the layer width (0.48 nm) [30]. The basal spacing and the gallery height of L1, L2, L4, and L5 are shown in **Table 2**. It indicates that the intercalation of EDTA into NO3-LDHs gives rise to an increase of basal spacing. This basal spacing could identify the existence of EDTA, because it is close to the dimensions of EDTA complexes (0.9 nm<sup>−</sup><sup>1</sup> nm) founded by single crystal XRD of M-EDTA (M—metallic ions) compound [12, 17, 30, 32].

#### **3.4 SEM micrographs**

SEM images of all composite synthesized in this work are shown in **Figure 7**. These adsorbents have clear plate-like morphology, which is typical for LDHs [33]. The intercalated product particles are more homogeneous than the precursor product

**Figure 5.** *XRD patterns of (a) L1, (b) L2, and (c) L3.*
