# Carbon from Bagasse Activated with Water Vapor and Its Adsorption Performance for Methylene Blue
## 3 Results and Discussion
Additionally, the peaks at 1093, 1570, 2884, and 3446 cm\({}^{-1}\) are decreased in terms of peak intensity and shifted to 1117, 1580, 2894, and 3421 cm\({}^{-1}\). These results are consistent with previous reports [32; 57]. The differences in IR spectra before and after MB adsorption could be connected to the possible interaction of MB functional groups on the activated-carbon surface during the adsorption process [58]. The interaction between organic compound with carbon can be \(\pi\rightarrow\pi\) electron-donor acceptor, hydrophobic interaction, hydrogen bonding, electrostatic and covalent interaction, and Van der Waals forces, which could work individually or simultaneously [55]. The hydrophobic side of carbon provides a high \(\pi\) electron of sp\({}^{2}\) carbons, in which MB molecules interact through \(\pi\)-\(\pi\) electron coupling. The \(\pi\)-\(\pi\) interaction is specifically in between \(\pi\) systems of carbonaceous material with the C=C or benzene ring of the MB [52]. Concurrently here, MB is a cationic dye that would bear a positive charge within an aqueous solution by releasing CI 'ions. The positive part would interact easily with the high electron-rich \(\pi\) orbital [53] or negatively charged surface of carbon using an electrostatic interaction [54]. The \(\pi\)-\(\pi\) interaction is specifically within \(\pi\) systems of carbonaceous material with the C=C or benzene ring of the MB [52]. At the same time, MB is a cationic dye that would bear a positive charge within an aqueous solution by releasing CI 'ions. The positive part would interact easily with the high electron-rich \(\pi\) orbital [53] or negatively charged surface of carbon [54], as described in Figure 9.  
A kinetic study was applied to the initial adsorption, the adsorption before it reached equilibrium, which was 30 min for this research. After reaching the equilibrium, the adsorption rate is similar to the desorption rate. The kinetics data are listed in Table 4. The linear fitting of the second-order reaction showed a higher adj. R\({}^{2}\) indicates that the initial rate of adsorption followed a second-order reaction. The result were similar to the rate of removal of MB onto hydroxyapatite nanoparticles [33]. The adsorption thermodynamic showed  
Figure 10: FTIR spectrum of AC700: before and after MB adsorption. negative values of \(\Delta\)G, confirming a spontaneous and thermodynamically favorable adsorption. It is generally accepted that physisorption occurs between \(-20\) and \(0\) kJ/mol, while chemisorption is in between \(-80\) and \(-400\) kJ/mol [59]. Moreover, the positive value of the enthalpy changes, \(1.48\times 10^{-4}\) kJ/mol indicated endothermic adsorption, and the entropy change of \(0.0408\) kJ/mol.K confirmed a small increase of irregularity. Table 5 summarizes the literature data on the MB adsorption parameters obtained for different carbon materials. The diffusion rate was studied by applying a Weber-Morris plot, as shown by Figure 11. The diffusion constant C was not zero. C \(\
eq\) 0 indicates the complexity of the adsorption process. The two-linearity on the plots indicates either intra-particle diffusion or external diffusion, the diffusion in between the boundary layer of adsorbent-adsorbate, which controls the process of adsorption [60]. The first step of adsorption was assigned to the transport of MB molecules to the external surface of the AC700, and then the second step was the transport into the micro/mesoporous structure of the adsorbent, followed by the adsorption at the surface of adsorbent or AC700 [61].