# Fine Activated Carbon from Rubber Fruit Shell Prepared by Using ZnCl\({}_{2}\) and KOH Activation
## 3 Results
### Characterization of RFSFACs
The following equation may describe the reaction on a carbon surface (C\({}_{\rm f}\)) using KOH activation [44; 45]:  
\[2{\rm KOH}\rightarrow{\rm K_{2}O}+{\rm H_{2}O}\;({\rm dehydration}) \tag{1}\]  
\[{\rm C_{f}}+{\rm H_{2}O}\rightarrow{\rm H_{2}}+{\rm CO}\;({\rm water-gas}\;{\rm reaction}) \tag{2}\]  
\[{\rm CO}+{\rm H_{2}O}\rightarrow{\rm H_{2}}+{\rm CO_{2}}\;({\rm water-gas}\;{\rm shift }\;{\rm reaction}) \tag{3}\]  
\[{\rm K_{2}O}+{\rm CO_{2}}\rightarrow{\rm K_{2}CO_{3}}\;({\rm carbonate}\;{\rm formation}) \tag{4}\] \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Proximate Analysis (Weight \%)**} & \multirow{2}{*}{**RFSFC Powder**} & \multicolumn{6}{c}{**KOH**} & \multicolumn{6}{c}{**ZnCl\({}_{2}\)**} \\ \cline{3-8}  & & \multicolumn{6}{c}{**RFSFC Powder**} \\ \cline{3-8}  & & **1** & **2** & **3** & **4** & **5** & **6** \\ \hline Moisture & 0.43 & 16.76 & 20.61 & 23.51 & 13.31 & 13.76 & 14.98 \\ Volatile matter & 97.06 & 56.38 & 47.37 & 42.24 & 48.24 & 34.90 & 33.44 \\ Fixed carbon & 1.05 & 16.26 & 21.25 & 23.84 & 23.26 & 36.97 & 38.09 \\ Ash & 1.46 & 10.59 & 10.77 & 10.41 & 15.19 & 14.38 & 13.50 \\ \hline \hline \multicolumn{8}{c}{**Elemental Contents (Atomic \%)**} \\ \hline Carbon & 74.11 & 72.29 & 77.63 & 78.40 & 65.94 & 81.83 & 80.05 \\ Oxygen & 11.06 & 27.65 & 19.92 & 18.73 & 23.77 & 12.67 & 17.42 \\ Nitrogen & 13.66 & - & - & - & - & - & - \\ Silicon & 0.16 & 0.05 & 0.61 & 0.37 & 0.93 & 0.03 & 0.10 \\ Potassium & 0.86 & - & 1.84 & 2.5 & 0.08 & 0.02 & 0.07 \\ Chlorine & - & - & - & - & 4.41 & 3.45 & 1.25 \\ Zinc & - & - & - & - & 4.86 & 2.00 & 1.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Proximate analysis results and elemental contents before and after the activation process with different activating agents and impregnation ratios. Figure 1: Thermal decomposition analysis results for RFSAC products prepared using different activating agents and impregnation ratios. During the activation process, K2 CO3 was formed, and the carbon was simultaneously reduced to K, K2O, and CO2, and a porous carbon surface was also developed. The metal of K was created at a temperature above 700 \({}^{\circ}\)C during activation of the K2O. The potential reaction could be as follows [45,46]:  
\[\text{K}_{2}\text{O}+\text{H}_{2}\to 2\text{K}+\text{H}_{2}\text{O}\ \text{(reduction by hydrogen)} \tag{5}\]  
\[\text{K}_{2}\text{O}+\text{C}_{\text{f}}\to 2\text{K}+\text{CO}\ \text{(reduction by carbon)} \tag{6}\]  
\[\text{K}_{2}\text{CO}_{3}+2\text{C}\to 2\text{K}+\text{3 CO}\ \text{(reduction by carbon)} \tag{7}\]  
Because the boiling point of K is 780 \({}^{\circ}\)C [44] and the activation process was carried out at 800 \({}^{\circ}\)C, there is a significant loss of potassium metal in the activated carbon. The XRD patterns, presented in Figure 2a, show that the activated RFSFAC products prepared using KOH have an amorphous carbon structure. The presence of broad peaks at around 26.69\({}^{\circ}\) and 43.24\({}^{\circ}\) indicates that the carbon layer planes are aligned [47]. Referring to the TGA results in Figure 1, it can be observed that the ZnCl2-activated samples (RFSFAC4-6) experience a weight loss of around 80% by the end of the heating process. The significant reduction in mass that occurs over the temperature range from 150 to 450 \({}^{\circ}\)C can be attributed to the release of moisture from the solid-phase ZnCl2. The more gradual reduction in mass from 450 to 650 \({}^{\circ}\)C is, then, the result most likely of volatile evolution, while that at temperatures higher than 700 \({}^{\circ}\)C reflects the total evaporation of the liquid phase from the ZnCl2. Previous studies have reported that ZnO/carbon compounds are formed at 550 \({}^{\circ}\)C and reduce to metallic zinc at temperatures higher than 800 \({}^{\circ}\)C [21]. These findings are supported by the XRD patterns shown in Figure 2b for the present RFSFACs activated using ZnCl2.