# Carbon from Bagasse Activated with Water Vapor and Its Adsorption Performance for Methylene Blue
## 3 Results and Discussion
The FTIR spectra of carbonized bagasse compare to the raw bagasse is depicted in Figure 4. Detailed comparison of each peak is listed in Table 1 along with the possible source of the functional groups based on some related references. Ash precipitation to carbonized bagasse indicated ash content of 5.17 \(\pm\) 0.29%, or total carbon content in the carbonized bagasse of 94.83 \(\pm\) 0.29%. Moreover, the elemental CHN analysis to AC700 found C:H:N:others of 58.65:0.45:0.20:40.70 (%), respectively [47]. The results appeared to be consistent with the TG-DT analysis for the wet activated-carbon that was conducted to understand the interaction between steam or water molecules with the carbon that occurred under activation temperature, which was proven by an exothermic peak centered  
Figure 3: The optical image of carbonized bagasse (**a**), and SEM images of carbonized bagasse at different magnification: (**b**) 1000\(\times\) and (**c**) 5000\(\times\). at 526.88 \({}^{\circ}\)C (see Figure 5). This indicated that the decomposition of the carbon skeleton to form CO\({}_{2}\)[38; 39] caused weight reduction up to 22.62%, as presented in the TG-DTA curve, shown in Figure 6, for the wet activated-carbon at the furnace. Activation at 700 \({}^{\circ}\)C produced a carbon yield of 96.54 \(\pm\) 4.83% from the carbonized bagasse, or 22.84 \(  
Surface morphology analysis, as shown in Figure 6, found that the activation opened the channels within char blocks and spread over into small pieces, allowing the increase of surface area, as recorded in Table 2.  
N\({}_{2}\) adsorption analysis found that the carbonized bagasse had only 24.8 m\({}^{2}\)/g of surface area with a very low total pore volume of 4.0 \(\times\) 10\({}^{-3}\) cc/g (Table 2), which indicates that the pores of the carbonized bagasse were wide, with an average diameter of 3.2 nm; however, the channel was short. Activation seemed to clean out the pores, as they became deeper, and the total pore volume was increased, which resulted in a higher surface area, as can be seen in Table 2, in which the AC700 provided the highest total pore volume and surface area. The N\({}_{2}\) adsorption isotherm shows that the adsorption isotherm of carbonized bagasse and AC700 followed type IV, indicating mesopores that contributed to the adsorption with pore sizes of 2-50 nm [43; 50]. The meso-size pore was suitable for a macromolecule like methylene blue (MB). Even though the carbonized bagasse had the highest pore size of 3.2 nm, the very low surface area, however, caused low adsorption performance. AC700 showed a high surface area of 592.4 \(\pm\) 0.2 m\({}^{2}\)/g, even though the surface area was smaller than the carbon from bagasse, which was chemically activated by potassium hydroxide solution, i.e., 1620.69 m\({}^{2}\)/g [17], as well as with the carbon from bagasse, which was activated with ZnCl\({}_{2}\), i.e., 916.134 m\({}^{2}\)/g [21]. However, the activation with steam was preferable with regards to environmental issues. The MB adsorption on AC700 followed a type IV isotherm, indicating the high contribution of the large pore size. The pore size distribution curve (see Figure 7) showed that the AC700 provided the pore distribution at a larger size over 2 nm. Due to its highest surface area and mesopores available within the AC700, therefore for adsorption tests with such macromolecule as methylene blue (MB), AC700 was chosen. Another previous adsorption study was conducted for water vapor or as a dehumidifier [47]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**The Prepared Materials** & \multicolumn{2}{c}{**Surface Area**} & **Total Pore Volume** & \\
**Multi Point BET (m\({}^{2}\)/g)** & **(\(\times\)10\({}^{-1}\) cc/g)** & **Average Pore Size (nm)** \\ \hline Carbonized bagasse & 24.8 \(\pm\) 0.0 & 0.4 & 3.2 \\ AC500 & 366.7 \(\pm\) 0.1 & 2.1 & 1.1 \\ AC600 & 465.6 \(\pm\) 0.1 & 2.9 & 1.2 \\ AC700 & 592.4 \(\pm\) 0.2 & 4.7 & 1.6 \\ \hline \hline \end{tabular}
\end{table}