## 3 Results and Discussion
### Characterization of AC Waste
#### 3.1.2 Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS)  
Investigations of AC Waste  
The correctness of the X-ray fluorescence (XRF) results of ACMs was also controlled by SEM investigations; this was, based on EDS determining and mapping the element distributions through the color and morphology characteristics of asbestos.  
The morphological study of the asbestos-cement sample surface at various magnifications (Figure 1a-e) showed the rough and inhomogeneous distribution of asbestos fibers.  
At some locations on the surface of this compact composite material sample, bundles of asbestos fibers composed of primary fibers are clearly visible. The length of the fibers exceeded a few hundred micrometers and their thickness was less than 1 \(\upmu\)m. EDS analysis was carried out on the whole area of the samples, see Figure 1c,e.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Components**} & \multicolumn{3}{c}{**Content (wt. \%)**} & \multirow{2}{*}{**Elements**} & \multicolumn{2}{c}{**Average Content**} \\ \cline{2-2} \cline{4-6}  & **Sample 1** & **Sample 2** & **Sample 3** & & **(wt. \%)** \\ \hline SiO\({}_{2}\) & 20.67 & 19.14 & 20.30 & Si & 9.36 \\ CaO & 40.02 & 38.82 & 40.54 & Ca & 28.44 \\ MgO & 5.85 & 5.65 & 5.36 & Mg & 3.39 \\ Al\({}_{2}\)O\({}_{3}\) & 2.98 & 3.02 & 2.40 & Al & 0.74 \\ Fe\({}_{2}\)O\({}_{3}\) & 2.16 & 2.20 & 2.05 & Fe & 0.74 \\ SO\({}_{3}\) & 2.34 & 2.53 & 2.35 & S & 0.96 \\ P\({}_{2}\)O\({}_{5}\) & 0.12 & 0.11 & 0.10 & P & 0.02 \\ K\({}_{2}\)O & 0.34 & 0.31 & 0.29 & K & 0.13 \\ Cl & 0.02 & 0.02 & 0.02 & Cl & 0.02 \\ LOI \({}^{*}\) & 25.30 & 25.90 & 26.60 & - & - \\ Others & 0.20 & 2.30 & - & - & - \\ \hline \hline \end{tabular}
\end{table}
Table 2: Chemical analysis of asbestos–cement (AC) waste samples (* loss on ignition).  
Figure 1: \(Cont\).  
The resulting contents obtained from the whole area of the asbestos-cement samples (Figure 1c,e) and point marked with a green cross (see Figure 1a) are compared in Table 3.  
Relatively large differences in the elemental analysis of the sample area and the individual point on the micrographs of different magnification were recorded. These differences observed in the content of elements are related to the composition heterogeneity. The highest content of magnesium was in the place where asbestos fibers predominate in the cement matrix.  
The distribution of all and the selected elements on the whole area of the AC sample identified by EDS mapping is illustrated in Figure 4. Here, the inhomogeneity of the fiber bundles' distribution can be observed.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Element**} & \multicolumn{3}{c}{**Content (wt. \%)**} \\ \cline{2-4}  & **Area 1** & **Area 2** & **Point** \\ \hline Si & 4.35 \(\pm\) 0.32 & 9.79 \(\pm\) 0.36 & 12.39 \(\pm\) 0.39 \\ Ca & 54.75 \(\pm\) 1.48 & 31.70 \(\pm\) 0.80 & 8.20 \(\pm\) 0.21 \\ Mg & 2.28 \(\pm\) 0.26 & 1.33 \(\pm\) 0.09 & 14.43 \(\pm\) 0.57 \\ Al & 3.55 \(\pm\) 0.30 & 0.63 \(\pm\) 0.06 & - \\ Fe & - & - & 1.25 \(\pm\) 0.07 \\ K & - & 0.52 \(\pm\) 0.50 & - \\ O & 22.05 \(\pm\) 5.86 & 34.31 \(\pm\) 3.78 & 33.47 \(\pm\) 2.81 \\ C & 2.05 \(\pm\) 1.15 & 6.48 \(\pm\) 1.00 & 9.12 \(\pm\) 0.94 \\ Au & 6.39 \(\pm\) 0.47 & 15.25 \(\pm\) 0.50 & 21.14 \(\pm\) 0.59 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Elemental analysis of the whole area of asbestos–cement sample (Area 1—Figure 1c; Area 2—Figure 1e) and at a selected point (Figure 1a).  
Figure 3: EDS spectrum of the sample from Figure 1e.