## 3 Results  
### Characterization of DSD Samples  
Results of X-ray powder diffraction of DSD sample are presented in Figure 1. XRD pattern shows a diffractometric reflects of clay minerals (illite and kaolinite) and others mineral phases. Illite phase displays peaks at 10.0 and 4.96 A. Two peaks are appeared at 7.15 and 3.49 A which corresponds to kaolinite clay. This finding is in a good agreement with the study of [PERSON] et al. (2019) [28]. The XRD spectrum also confirms that DSD material contains quartz (Q), calcite (Ca), and dolomite (D) as non-clay minerals.  
The chemical analysis values for the sample are represented in Table 3 and show that the main oxides detected in DSD are S\({}_{1}\)O\({}_{2}\), CaO, Al\({}_{2}\)O\({}_{3}\), Fe\({}_{2}\)O\({}_{3}\), and MgO. Composition of the studied sediment shows the predominance of silica (S\({}_{1}\)O\({}_{2}\)) and alumina (Al\({}_{2}\)O\({}_{3}\)) mineral of the illite and kaolinite clays. CaO and MgO content indicate the presence of calcite (CaCO\({}_{3}\)) and dolomite (Ca Mg (CO\({}_{3}\))\({}_{2}\)) [16]. The content of Fe\({}_{2}\)O\({}_{3}\) and K\({}_{2}\)O confirms the presence of illite phase [29]. As can also be observed, the percentage of iron oxide is important, which gives the sediment its red color.  
The infrared spectrum (IR) of the DSD sample is shown in Figure 2, which revealed important information. The presence of quartz in the powder is indicated by the two bands near 700 cm\({}^{-1}\) and 800 cm\({}^{-1}\), which confirm the XRD results. The vibration bands appearing at 1430 cm\({}^{-1}\) are attributed to the carbonate in the form of calcite or dolomite [30]. The band detected near 3620 cm\({}^{-1}\) corresponds to the stretching vibrations of coordinated water [31]. The (Si-O) of the silicate structure corresponds to the very strong absorption band at 1013 cm\({}^{-1}\).  
Figure 1: X-ray diffraction pattern of DSD sample.  
\begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline
**Parameters** & **S\({}_{1}\)O\({}_{2}\)** & **CaO** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **MgO** & **SO\({}_{3}\)** & **K\({}_{2}\)O** & **Na\({}_{2}\)O** & **P\({}_{2}\)O\({}_{5}\)** & **TiO\({}_{2}\)** & **SrO** \\ \hline Percentage & 38.03 & 18.99 & 11.83 & 4.93 & 3.70 & 2.19 & 1.64 & 0.18 & 0.18 & 0.65 & 0.11 \\ \hline \end{tabular}
\end{table}
Table 3: Chemical composition (_url_ %) of the DSD material.  
Figure 2: FTIR spectrum of DSD sample.  
Figure 3 shows the physisorption isotherm of the N\({}_{2}\) gas adsorption-desorption of the DSD sample. All the textural characteristics (i.e., properties of specific surface and pores) are calculated from data of this analysis. According to the IUPAC nomenclature, the N\({}_{2}\) plot belongs of type IV with a H\({}_{3}\) hysteresis loop which appeared at pressure (P/P\({}_{0}\)) higher than 0.3. This result suggested that the SDS material has a predominantly mesoporous structure (Vmesopore = 94.4%) with average pores diameter centered at 9.18 nm [32]. Data in Figure 3 show also that the DSD material exhibited a good surface area (S\({}_{\text{BET}}\) = 39.08 m\({}^{2}\)/g) but relatively low total pore volume (V\({}_{\text{Total}}\) = 0.089 cm\({}^{3}\)/g).  
The zero-point charge pH (pH\({}_{\text{PZC}}\)) of the DSD adsorbent was found at 7.81 (Figure 4a), which indicates the basic nature of its surface. At this point of pH, the overall surface charge of the material is zero [33]. When the pH of the solution is higher than pH\({}_{\text{PZC}}\), the DSD surface will be negatively charged, and vice versa [34]. This can also provide insight into the role of electrostatic interactions in the adsorption mechanism [35]. In this study, the adsorption experiments of isotherm were performed at pH = 7.0, implying that the DSD's surface was mostly positively charged and the ion exchange can occur.