## 3 Results
### Thermodynamics Behaviors  
The calculation of thermodynamic parameters is indispensable component to determine the adsorption mechanisms (e.g., chemical or physical). The enthalpy change (\(\Delta\)H\({}^{\circ}\)) and entropy change (\(\Delta\)S\({}^{\circ}\)) were calculated from the slope and intercept of InKC versus 1/T (Figure 8). Results demonstrate that the Gibbs free energy is negative (\(-\Delta\)G\({}^{\circ}\)), showing that the adsorption process is spontaneous and favorable at the tested temperatures without any additional prerequisites (i.e., heating).  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Textural Properties**} & \multicolumn{4}{c}{**Conditions of Adsorption Isotherm**} & \multicolumn{1}{c}{**Q\({}^{\circ}\)max**} & \multicolumn{1}{c}{**Reference**} \\ \cline{2-9}  & \(S_{\text{BET}}\) & \(V_{\text{total}}\) & \(m/V\) (g/L) & pH & \(t\) (h) & \(C_{\text{o Range}}\) & **T** (\({}^{\circ}\)C) & **(mg/g)** & **Reference** \\  & **(m\({}^{2}\)g)** & **(cm\({}^{3}\)g)** & **m/V** (g/L) & pH & \(t\) (h) & \(C_{\text{o Range}}\) & **T** (\({}^{\circ}\)C) & **(mg/g)** & **Reference** \\ \hline Raw smectite clay & 74.0 & 0.19 & 0.5 & - & 24 & 12.5–100 & - & 86.5 & [37] \\ Surfactant modified bentonite & 27.9 & 0.24 & 0.2 & 9.0 & 4 & 81.6–408 & 30 & 149 & [48] \\ Zoolite–Montmorillonite & 19.27 & 0.12 & 1 & 9.0 & 24 & 20–150 & 25 & 68.7 & [49] \\ adsorbent & & & & & & & & \\ Cu(II)-loaded & 83.0 & - & 1.0 & 8.2 & 5 & 10-100 & 25 & 114.3 & [50] \\ Montmorillonite & & & & & & & & \\ Natural clay & 128.0 & 0.32 & 0.5 & 7.5 & 3 & 90–300 & 30 & 330.0 & [6] \\ Palm Petioles biochar & 640.0 & 0.403 & 1.0 & 7.0 & 24 & 5–250 & 20 & 196.5 & [7] \\ Woody biochar & & & & & & & & \\ (at 700 \({}^{\circ}\)C) & 808.0 & 0.89 & 2.0 & 8.0 & 4 & 5–200 & 30 & 125.5 & [51] \\ DSD & 39.08 & 0.089 & 1.0 & 7.0 & 4 & 4–250 & 20 & 183.6 & This study \\ DSD & 39.08 & 0.089 & 1.0 & 7.0 & 4 & 4–250 & 35 & 198.0 & This study \\ DSD & 39.08 & 0.089 & 1.0 & 7.0 & 4 & 4–250 & 50 & 243.6 & This study \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of the monolayer adsorption capacity (Q\({}^{\circ}\)max) of CV Dye onto DSD material to different adsorbents reported in the literature.  
Figure 8: Thermodynamic plot for the adsorption of CV dye onto DSD adsorbent.  
In general, \(\Delta\)G\({}^{\circ}\) value for a process dominated by physisorption is in the range of \(-20\) to \(0\) KJ/mol, whereas it is between \(-400\) and \(-80\) KJ/mol for chemical adsorption [52]. Therefore, \(\Delta\)G\({}^{\circ}\) values are between 28.2 and 30.7 kJ/mol for the range studied of temperatures (from 293 K to 323 K), indicating that the adsorption process was controlled by both ion exchange and physical interactions (i.e., pore filling) in our case. [PERSON] et al. (2014) [53] reported that the ion exchange is the predominate mechanism for \(\Delta\)G\({}^{\circ}\), ranging from \(-34\) to \(-40\) kJ/mol.  
On the other hand, the value of the standard change in enthalpy is negative (\(-\Delta H^{\circ}\)), indicating an exothermic process (Table 7). Several scholars have found a similar trend in the exothermic nature of the adsorption of cationic dyes onto various materials, such as natural clay [6], illite/kaolinite [45], and Montmorillonite [36]. Furthermore, the positive value of \(\Delta\)S\({}^{\circ}\) reflected that the organization of the CV dye molecules at the solid/liquid interface becomes more random during the sorption operation [7], and the reaction is a thermodynamically favorable [53]. In general, findings from this study contribute significantly on the development of new natural adsorbents for remediation of polluted water [54,55]. Although various natural adsorbents have been used for removal of pollutions [56, 57, 58, 59, 60], the use of dredging sediment employed in this study suggested that natural clays that are freely available have the potential not only for dye removal but also for other pollution removal.