## 3 Results and Discussion
### Instrumental Analysis
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variable** & **Raw Vermiculite** & \
\begin{tabular}{c} **Base-Activated** \\ **Vermiculite** \\ \end{tabular} &
\begin{tabular}{c} **Acid–Activated** \\ **Vermiculite** \\ \end{tabular} \\ \hline Specific surface area (m\({}^{2}\)/g) & 29.93 & 2.152 & 2.777 \\ Average pore diameter (mm) & 0.558 & 1.487 & 1.737 \\ Mesopor diameter (mm) & 38.73 & 38.73 & 21.433 \\ Bulk density \(d_{b}\) (g/cm\({}^{3}\)) & 0.2393 \(\pm\) 0.0012 & 0.2460 \(\pm\) 0.0018 & 0.2775 \(\pm\) 0.0031 \\ Apparent density \(d_{p}\) (g/cm\({}^{3}\)) & 1.4893 \(\pm\) 0.0032 & 1.5550 \(\pm\) 0.0929 & 1.6757 \(\pm\) 0.1118 \\ Actual density \(d_{a}\) (g/cm\({}^{3}\)) & 2.3427 \(\pm\) 0.0060 & 2.4381 \(\pm\) 0.0213 & 2.6923 \(\pm\) 0.0443 \\ Relative density (\%) & 10.21 \(\pm\) 0.20 & 10.09 \(\pm\) 0.08 & 10.31 \(\pm\) 0.07 \\ Total porosity (\%) & 89.79 \(\pm\) 0.20 & 89.91 \(\pm\) 0.08 & 89.69 \(\pm\) 0.07 \\ Open porosity (\%) & 83.93 \(\pm\) 0.38 & 84.18 \(\pm\) 0.02 & 83.44 \(\pm\) 0.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Parameters of microstructural raw and activated vermiculite. Figure 2: Distribution of pore volume relative to pore width: (**A**) Raw vermiculite, (**B**) basic-activated vermiculite, (**C**) acid–activated vermiculite. Figure 5 shows the SEM micrographs of vermiculite before and after Ag\({}^{+}\) and Cu\({}^{2+}\) adsorption. The microphotographs analysis revealed a plate structure of vermiculite [36; 37]. The EDS technique revealed the presence of a number of elements. The base-activated material additionally contains sodium, which suggests the replacement of Mg\({}^{2+}\) with Na\({}^{+}\)[36]. After adsorption of silver ions, the material additionally contained silver or copper. The presence of both elements on the surface of vermiculite confirmed the effectiveness of the adsorption process. Table 5 presents a comparison \begin{table}
\begin{tabular}{c c c} \hline \hline
**Vermiculite FTIR Peaks [cm\({}^{-1}\)]** & **Assignment** & **References** \\ \hline
440–450 & Si––O–Si bending vibration & [30] \\
670–80 & Si–O–Si asymmetric stretching & [31] \\
730–760 & Al–O coordination & [32] \\
1000–1010 & Si–O asymmetric stretching & [33] \\
1100–1125 & Si–O–Si asymmetric stretching & [30] \\
1350 & N=O stretching & [32] \\
1630–1650 & O–H bending mode & [34] \\
3350–3450 & O–H stretching & [35] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: FTIR characteristic peaks of vermiculite before and after Ag\({}^{+}\)/Cu\({}^{2+}\) adsorption. Figure 4: FTIR analysis of vermiculite: A–raw vermiculite, B–NaOH-activated vermiculite, C–citric acid-activated vermiculite, D–vermiculite after the adsorption of silver ions, E–vermiculite after the adsorption of copper ions. Figure 3: X–ray diffraction of vermiculite before and after Ag\({}^{+}\) or Cu\({}^{2+}\) adsorption: A–raw vermiculite, B–NaOH–activated vermiculite, C–citric acid-activated vermiculite, D–vermiculite after the adsorption of silver ions, E–vermiculite after the adsorption of copper ions. of the maximum sorption capacities for metal ions of the raw and modified vermiculite found in the literature. Modified vermiculite is characterized by a higher sorption capacity compared to the raw material, which confirms a beneficial effect of activation processes on vermiculite. Figure 5: SEM images and EDS patterns of vermiculite: (**a**) Raw vermiculite, (**b**) NaOH–activated vermiculite, (**c**) citric acid–activated vermiculite, (**d**) after the adsorption of Ag\({}^{+}\). (**e**) after the adsorption of Cu\({}^{2+}\).