## 3 Results
### DSC-TG/MS Measurements  
DSC-TG/MS measurements of the wollastonite raw material (educt) and the carbonated wollastonite (CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\), 333 K, 2 MPa) were carried out to determine the full content of water and carbonate (Table 3). This was necessary because X-ray amorphous carbonate could not be determined directly with PXRD, when additional phases (SiO\({}_{2}\)) contributed to the total amorphous content [6]. DSC-TG/MS measurements (Figure 2a) were carried out by [PERSON] et al. [6] with the raw material. Figure 2b represents the results of DSC-TG/MS measurements of carbonated wollastonite (24 h CO\({}_{2}\), 333 K, 2 MPa). During the measurement of the raw material, the weight loss was 2.1%, from which 1.7 wt.% could be associated with CO\({}_{2}\). Hence the original content amounts to 3.9 wt.% carbonate (CaCO\({}_{3}\)) in the sample (Figure 2a, Equation (2)). The Rietveld analysis (5 wt.%) and the DSC-TG (4 wt.%) measurements of the raw material for the CaCO\({}_{3}\) exhibited similar values [6]. DSC-TG/MS/IR analysis of the carbonated wollastonite (24 h CO\({}_{2}\), 333 K, 2 MPa), shown in Figure 2b, was carried out. During heating, a weight loss of 24.4% was recorded. From which 23.9 wt.% could be attributed to CO\({}_{2}\). According to Equation (2), the original content of carbonate was 54.8% (Figure 2b). The results of the Rietveld method and the DSC-TG measurements of the carbonated wollastonite for the content of carbonate showed again similar results (Rietveld: 50%; DSC-TG: 55%) [6]. Thermal (DSC-TG) and spectroscopic (MS) analyses on previously treated wollastonite with CO\({}_{2}\) and SO\({}_{2}\)/NO\({}_{2}\) (-70 ppm each) at 333 K and 2 MPa is shown exemplarily in Figure 3. During \begin{table}
\begin{tabular}{c c c c} \hline
**Temperature [K]** & **Carbonation Medium** & **Gas Composition** & **Pressure [MPa]** & **Reaction Time [h]** \\ \hline
333 & water & CO\({}_{2}\) & 2 & 24 \\
333 & brine & CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\) & 2 & 0, 3, 6, 12, 18, 24 \\ \hline \end{tabular}
\end{table} 
Table 2: Overview of performed series of experiments at constant pressure and temperature and varied time. \begin{table}
\begin{tabular}{c c c c c} \hline
**Reaction Time [h]** & **Gas Composition** & **Weight Loss [\%]** & **CO\({}_{2}\) Content [wt.\%]** & **Calculated Content of CaCO\({}_{3}\) [wt.\%]** \\ \hline
0 & & 2.1 & 1.7 & 3.9 \\
3 & CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\) & _7.6_ & _7.0_ & 16.1 \\
6 & CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\) & 13.4 & 12.2 & 28.0 \\
12 & CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\) & 20.2 & 18.6 & 42.7 \\
18 & CO\({}_{2}\) + SO\({}_{2}\) + NO\({}_{2}\) & 22.4 & 21.4 & 49.0 \\
24 & CO\({}_{2}\) + SO\(heating, 25.9% of the weight was lost; 24.4% could be attributed to CO\({}_{2}\), i.e., to 56 wt.% carbonate in the sample (Figure 3, Table 3, Equation (2)). The MS curve (green) detected a maxima of the mass flow of H\({}_{2}\)O (Figure 3) at approximately 400 K, which decreased distinctly at 500 K. From 500 to 700 K the release of H\({}_{2}\)O increased again and dropped afterwards until 1050 K. The MS curve of CO\({}_{2}\) (Figure 3, magenta line) remained at a constant level until 700 K and increased slightly until 900 K, then it increased more distinctly and held a plateau until 950 K. Afterwards, a maximum at 1100 K was reached. At temperatures beyond 1100 K, no significant release of CO\({}_{2}\) could be observed. The TG curve (weight loss, Figure 3, black line) decreased with a small rate until 900 K. The loss of CO\({}_{2}\) could be observed clearly in the curve between 900 and 1080 K. Beyond 1100 K, the release of CO\({}_{2}\) stopped. The DSC signal (Figure 3, blue line) showed a maximum (endothermic) amplitude at 1080 K and correlated with the detected MS maximum of CO\({}_{2}\). At approximately 1150 K, a positive amplitude for the DSC signal could be observed and indicated the formation of Ca\({}_{2}\)SiO\({}_{4}\) (i.e., C\({}_{2}\)S, larnite), which was confirmed by PXRD of the TG sample.