# CO\({}_{2}\) Adsorption Reactions of Synthetic Calcium Aluminum Ferrite (CAF)
## 3 Result and Discussion
### Characteristics of Carbo Reaction of SCAF  
#### 3.2.1 Analysis of Thermal Properties by Carbo Reaction of SCAF  
In order to investigate the reactivity of SCAF with CO\({}_{2}\), carbonation was conducted in two methods: a gas-solid reaction (dry method) with direct reaction between SCAF powder and CO\({}_{2}\), and a gas-liquid reaction (wet method) in which SCAF powder is dispersed in water (binder:water = 1:1) to form a slurry state and is reacted with CO\({}_{2}\). The absorption reaction time was set to 30 min, 1 h, 3 h, and 6 h, with the sampling carried out in line with the set time. In addition, thermogravimetry analysis (TGA) was performed to determine the amount of CO\({}_{2}\) adsorption with the reaction time. Figure 3 shows the results of thermogravimetric analysis of SCAF with different reaction times and sintering temperatures.  
The results of thermogravimetric analysis can be divided into three temperature sections, and Table 1 outlines the weight loss for each section by sintering temperature. The first section shows a weight reduction due to decomposition of water, and the second section is judged to be a weight loss due to Ca(OH)\({}_{2}\). The final section shows the weight loss due to the decomposition of calcite at 700-900 \({}^{\circ}\)C, which is considered to be a typical characteristic of thermal decomposition of calcite produced by the reaction between SCAF and CO\({}_{2}\)[8,9].  
Figure 4 shows the content of calcite (CaCO\({}_{3}\)) as a percentage based on the CO\({}_{2}\) reaction time. It can be seen that the generation of calcite increases with elapse of the reaction time, and as for the CO\({}_{2}\) reactivity, as shown in the XRD analysis result, more calcite generation is observed at a sintering temperature of 1000 \({}^{\circ}\)C than of 1100 \({}^{\circ}\)C. This is  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & & **1000 \({}^{\circ}\)C** & & & **1100 \({}^{\circ}\)C** & \\ \hline \multirow{2}{*}{
\begin{tabular}{c} **Reaction** \\ **Time** \\ \end{tabular} } & \multirow{2}{*}{**Method**} & **1 st** & **2 nd** & **3 rd** & **1 st** & **2 nd** & **3 rd** \\  & & **Section** & **Section** & **Section** & **Section** & **Section** & **Section** \\  & & **100–200 \({}^{\circ}\)C** & **350–500 \({}^{\circ}\)C** & **600–900 \({}^{\circ}\)C** & **100–200 \({}^{\circ}\)C** & **350–500 \({}^{\circ}\)C** & **600–900 \({}^{\circ}\)C** \\ \hline \multirow{3}{*}{30 min} & D & 0.56 & 0.24 & 0.05 & 0.54 & 0.38 & 0.11 \\  & W & 12.22 & 1.81 & 5.22 & 6.32 & 7.27 & 2.82 \\ \multirow{2}{*}{1 h} & D & 0.41 & 0.37 & 0.04 & 0.36 & 0.52 & 0.19 \\  & W & 8.69 & 6.56 & 6.51 & 7.89 & 7.14 & 4.28 \\ \multirow{2}{*}{3 h} & D & 0.47 & 0.22 & 0.18 & 0.40 & 0.54 & 0.22 \\  & W & 6.86 & 5.03 & 12.03 & 4.97 & 7.34 & 11.01 \\ \multirow{2}{*}{6 h} & D & 0.43 & 0.47 & 0.02 & 0.37 & 0.93 & 0.02 \\  & W & 6.89 & 1.33 & 13.67 & 2.27 & 6.12 & 12.93 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The weight lost (wt.%) with reaction time.  
thought to be due to unreacted lime, in which the reaction of the unreacted CaO with CO\({}_{2}\) led to more calcite formation [9,10].  
Figure 3: TGA curves of carbonation with (**a**) dry method and (**b**) wet method.