## 4 Results and Discussions
### Effect of Acid-Activation  
Changes in crystallinity resulting from acid activation of raw material were investigated by the X-ray powder diffraction patterns of some typical samples. Figure 6 presents the XRD patterns together of raw material S\({}_{0}\) and acid-activated clays (S\({}_{1}\), S\({}_{2}\), S\({}_{3}\)). The pattern of raw material is shown here for sake of comparison. It is observed that acid-activation causes a clear decrease in the crystallinity as indicated by decreasing intensity of the smectite peaks. Some of them are gradually deteriorated and completely disappeared. As it can be seen, XRD analysis has shown that clay acid-activation leads to total dissolution of calcite (reflections at 3.858; 3.04; 1.915 and 1.878 A) and gypsum (reflections at 2.09 A). Under strong conditions of H\({}_{2}\)SO\({}_{4}\), some of the quartz peaks are still present in the activated samples indicating that quartz is more resistant to acid attack than smectite. This result was similar to that found by [PERSON] and [PERSON] [13], hence quartz which appeared as the most abundant non-clay mineral in the natural clay (see reflections at d = 3.34; 2.28; 2.13; 1.819 A and d = 4.26 A) cannot be completely eliminated from clay by acid-activation. [PERSON] et al. [36] have reported similar results for montmorillonite activated by hydrochloric acid. For a greater extent of acid treatment (sample S\({}_{3}\)), it is observed that layered structure of clay mineral is indicated by the loss of crystallinity  
Figure 6: XRD patterns of raw material (**S\({}_{0}\)**) and acid-activated clay samples (**S\({}_{1}\), S\({}_{2}\), S\({}_{3}\)**). and the appearance of amorphous silica remaining from leached smectite phase. These results are in agreement with those obtained by [PERSON] et al. [37]; indicating that the acid-activated product of smectite is generally amorphous silica. Figure 7: \(Cont.\)  
X-ray diffraction patterns of oriented activated clay specimens (Figure 7S\({}_{1}\)-S\({}_{3}\)) prove a complete disappearance of the interstratified phase illite/smectite for the severity conditions but no effect on the kaolinite phase was observed (reflection at d = 7.18 A and d = 3.58 A). From these results, it can be concluded that acid treatment mainly affected the smectite phase and led to a partial decrystallization of the clay structure. The IR spectra presented in Figure 8 showed that the acid-activation led to a partial dissolution of the octahedral sheets especially with the sample S\({}_{3}\) prepared at high conditions of acid treatment. This is confirmed by the decrease in intensity of the band at 914 cm\({}^{-1}\) corresponding to \(-\)OH bending vibration (AlAlOH), bands at 530 cm\({}^{-1}\) assigned to (Si-O-Al), 1030 cm\({}^{-1}\) attributed to (Si-O) and band at 3430 cm\({}^{-1}\) related to adsorbed H\({}_{2}\)O.The broadening of the IR bands between 1100 and 900 cm\({}^{-1}\) is indicative of the formation of amorphous opal. In addition, a significant decrease or almost disappearance of the band at 3620 cm\({}^{-1}\) was observed, this is due to the important leaching of cations after the acid activation. The comparison between raw material and acid-activated clay IR spectra showed that for more severe conditions (S\({}_{3}\)), acid-activation destroys the smectite mineral phase as proved by the disappearance of the bands located between 3500 cm\({}^{-1}\) and 3700 cm\({}^{-1}\)[35]. The complete disappearance of bands at 1430 cm\({}^{-1}\) and 872 cm\({}^{-1}\) pointed out to the dissolution of calcite CaCO\({}_{3}\) and dolomite CaMg(CO\({}_{3}\)) for the three samples (S\({}_{1}\), S\({}_{2}\), S\({}_{3}\)) as previously reported by [PERSON] et al. [38]. Figure 7: XRD patterns of oriented activated clay specimens prepared under different conditions: \(\mathbf{S_{1}}\) (low conditions), \(\mathbf{S_{2}}\) (average conditions) and \(\mathbf{S_{3}}\) (strong conditions). Chemical analysis was performed on both raw material (S\({}_{0}\)) and acidified clays (S\({}_{1}\), S\({}_{2}\) and S\({}_{3}\)).