# Carbon from Bagasse Activated with Water Vapor and Its Adsorption Performance for Methylene Blue
## 3 Results and Discussion  
The bagasse was taken from a sugarcane factory located in Kudus, Central Java, Indonesia, during production time. EDX analysis found that the bagasse contained C, O, and Si with a composition of 43.47%, 56.08%, and 0.45%, respectively. The EDX spectra along with the optical and SEM images are depicted in Figure 1a, and the higher magnification SEM images are described in Figure 1b. SEM image shows cell wall flakes with some pits rarely spread on the wall. Thermal analysis of the bagasse provided the DTA-TGA curve as described in Figure 2. An exothermic peak revealed on the DTA curve at 304.2 \({}^{\circ}\)C was attributed to the decomposition of cellulose and hemicellulose in bagasse [35] in the range of 243.6-309.5 \({}^{\circ}\)C, providing 8.43% of mass loss. Another exothermic peak revealed at 417 \({}^{\circ}\)C indicated decomposition of lignin in bagasse, which hovered along 309.5-495 \({}^{\circ}\)C, caused, 9.05% mass loss, and remained carbon at above 495 \({}^{\circ}\)C. Considering the thermal analysis results, carbonization or the burning step to produce char was conducted at 600 \({}^{\circ}\)C.  
Carbonization at 600 \({}^{\circ}\)C under N\({}_{2}\) flow produced a black char, as described in the optical image (Figure 3a). The carbonization yield was 26.43% of the initial weight of bagasse, which was different than the TGA curve, as shown in Figure 2, in which only 17.48% content was released during heat treatment, leaving carbon at around 80%. The TG analysis was operated using a sample flask under vacuum; therefore, the sample was heated without any interactions with gas molecules in order to maintain carbon at rest. Moreover, during carbonization at 600 \({}^{\circ}\)C, most of the volatile components were released as pyrolysis gases [36], which was carried out by nitrogen flows. The pyrolysis gases were  
Figure 1: (a) EDX result of bagasse along with its optical and SEM images and (b) the higher magnification of SEM images. Figure 2: DTA-TGA curve of bagasse. the breakdown products of cellulose, hemicellulose, and lignin [37], in which the C-O and C-C functional groups from the cellulose, hemicellulose, and lignin were thermally broken down to form tar, H2O, CO, and CO2 and flushed out by nitrogen flows. During activation with steam, the char was in contact with H2O molecules. A thermal analysis of the wet activated-carbon found an exothermic peak centered at 528 \({}^{\circ}\)C, indicates the release of the carbon skeleton and CO2 release [38; 39], which indicates the interaction between water molecules with C, and the release of products, which causes weight reduction. Moreover, precipitation with NaOH followed by acid and water leaching found ash content of 5.17 \(\pm\) 0.29%, and the carbon content of carbonized-char was 94.83 \(\pm\) 0.29%. The SEM image of the carbonized-product in Figure 3b shows many channels formed in which the channels consisted of pores (Figure 3c) that regularly formed after the degradation of volatile components, cellulose, and lignin during carbonization. FTIR analysis found that after carbonization, some vibrations of the functional groups revealed, i.e., at 3422-3445 cm\({}^{-1}\), belonged to stretching vibrations of hydroxyl O-H and phenol hydroxyl groups [40; 41]. The intensity reduction of the O-H vibration peak confirmed the release of water molecules after the carbonization step. A small peak at 2883-2884 cm\({}^{-1}\) referred to C-H aliphatic stretching [42; 43]. A peak at 1712 cm\({}^{-1}\) referred to C=O stretching belonging to aldehydes, carboxylic acids, and ketones of cellulose or hemicellulose [44; 45]. A bond stretching of C=C aromatic was revealed at 1592-1570 cm\({}^{-1}\). Additionally, a C-O vibration and para substitution of benzene occurred at 1092-1223 cm\({}^{-1}\)[40; 46]. The intensity reduction of peak intensity of C=C aromatic, C=O stretching, and the C-O vibration confirmed the breakdown of cellulose and lignin during carbonization.