**2. Characterization of synthesized organoclays**

The organoclays synthesis and their characterization using various techniques have been published elsewhere [27].

#### **2.1 X-ray diffraction of raw clays and organoclays**

The **Figures 1a**, **b** and **2a**–**f** show the XRPD diffractograms of the AH and DI raw clays and the organoclays loaded at various loading levels (0.5 CEC, 1.0 CEC, 1.5 CEC and 2.0 CEC) of the C12, C14, C16, and 2C12 surfactants. **Figure 1** shows that AH and DI clays contain quartz, montmorillonite, kaolinite, hematite, rutile, orthoclase, and anorthite only for DI clay.

From **Figures 1** and **2**, it can be seen that the d001 basal spacing raises when the surfactant loading level increases. This increase indicates that the surfactant molecules are inserted into the mineral clay layers. It is also seen that an increase in the length of the long alkyl chain (C12, C14, and C16) and the number of long alkyl chains (C12 and 2C12) provokes an increase in the *d*<sup>001</sup> value (**Figures 1** and **2**). Furthermore, the increase in the *d*<sup>001</sup> values seems to take place in steps with preferred intervals, **Figures 1** and **2**.

As a matter of fact, the *d001* basal spacing value of the organoclays loaded at 2.0 CEC is 25 Å for the C12 surfactant (2.0 CEC-C12-AH and 2.0 CEC-C12- DI) < 32 Å and 28 Å for the C14 surfactant (2.0 CEC-C14-AH and 2.0 CEC-C14-DI, respectively) < 38 Å for the C16 and 2C12 surfactants (2.0 CEC-C16-AH and 2.0 CEC-C16-DI, 2.0 CEC-2C12-AH and 2.0 CEC-2C12- DI). In a previous study, Park reported that at 0.5 CEC loading level, a marginal increase of the basal spacing (*d*001) is observed when the long alkyl chain length increases: C12 (14.1 Å), C14 (14.3 Å), and C16 (14.4 Å) at a XRPD step size of 0.0167° for 2θ [28]. As a matter of principle, similar observation should be made in the present study for the *d*<sup>001</sup> spacing for all prepared organoclays

**Figure 1.**

*X-ray powder diffraction patterns of AH, DI clays and C12-AH, C12-DI organoclays. Q = quartz, M = montmorillonite, K = kaolinite, H = hematite, R = rutile, O = orthoclase, and A = anorthite.*

loaded at 0.5 CEC, **Figures 1** and **2**. This is related to the fact that at low loading level, the long alkyl chains are oriented parallel to the sheets, **Figures 3a** and **b**. The increase of the loading level, the length and the number of long alkyl chains in the quaternary alkylammonium cations increases the *d*<sup>001</sup> basal spacing, **Figures 1a**, **b** and **2a**–**f**. The obtained results indicate that the orientation of the inserted quaternary alkylammonium cations varies from being parallel with the sheets to turn to more and more upright when the loading level increases (**Figure 3**).

*Solid-State Synthesis of Organoclays: Physicochemical Properties and Application… DOI: http://dx.doi.org/10.5772/intechopen.107503*

**Figure 2.**

*X-ray powder diffraction patterns of AH, DI clays and C14-AH, C14-DI, C16-AH, C16-DI, 2C12-AH, and 2C12-DI organoclays. Q = quartz, M = montmorillonite, K = kaolinite, H = hematite, R = rutile, O = orthoclase, and A = anorthite.*

The increase of the quaternary alkylammonium cations loading level from 0.5 CEC to 2.0 CEC levels causes the expansion of the montmorillonite interlayers to 6.8 Å, 8.3 Å, 10.0 Å, 12.1 Å, 14.8 Å, 18.1 Å, 22.4 Å and higher than 28.3 Å and these expansion values depend on the clays (AH or DI) and/or on the surfactants (C12, C14, C16, and 2C12) used (**Figure 3**). Regarding the quaternary alkylammonium cations sizes, 8.3 Å and 10.0 Å as interlayer's expansions are attributed to a bilayer arrangement of the quaternary alkylammonium cations with an angle depending on the interaction between the quaternary alkylammonium cations and the clay layers, the chemical composition of the clay and the structure of the quaternary alkylammonium cations. This arrangement is expected for 18.0 Å and 19.7 Å as *d*<sup>001</sup> basal spacing. The pseudo-trilayer arrangement is expected for 12.1 Å and 14.8 Å as basal spacing expansion and the long alkyl chain of the surfactants are orientated in

**Figure 3.**

*Surfactant molecules orientations into the interlayer space: Arrangements (a) monolayer, (b) bilayers, and (c, d) pseudo-trilayers and (e, f and g, h) paraffin-type for one and two long alkyl chains respectively.*

an oblique plan. For 18.1 Å, 22.4 Å and 28.4 Å as expansions, the long alkyl chain are arranged in a paraffin-type and their orientation approaches to the alternate antiparallel packing in the clay interlayers as described in the crystal structures of the pure surfactants C12, C14 and C16 [29]. This paraffin-type arrangement is expected when the *d*<sup>001</sup> basal spacing values reach 27.8 Å, 32.1 Å or are higher than 38 Å. Therefore, the angle between the clay layers and the plane of the surfactant long alkyl chains approaches 90°. These proposed arrangements of the long alkyl chains in the organically modified clays interlayers are analogous to the arrangements reported by Lagaly et al. [30].
