# Carbon from Bagasse Activated with Water Vapor and Its Adsorption Performance for Methylene Blue
## 2 Materials and Methods
### Activated-Carbon Preparation  
The bagasse was chopped into small pieces and soaked in distilled water for 24 h. The water was then removed, and the cleaned bagasse was dried at 120 \({}^{\circ}\)C for 24 h in the oven. The dried bagasse was then burned in an installed-tube furnace at 600 \({}^{\circ}\)C for 30 min in N\({}_{2}\) atmosphere. The result was a black char or carbonized bagasse. A 460 \(\pm\) 5.6 mg quantity of the carbonized bagasse was then activated by water vapor or steam. The activation was done by heating the char at 500 \({}^{\circ}\)C, 600 \({}^{\circ}\)C, and 700 \({}^{\circ}\)C for 1 h under steam flow of 0.23 \(\pm\) 0.001 kg/h. The heating rate of both the carbonization and activation process was 18 \({}^{\circ}\)C\(\_\)min\({}^{-1}\). After 1 h, the temperature of the furnace was decreased to 30 \({}^{\circ}\)C, and then the activated-carbon was pulled out from the furnace and dried in the oven for 30 min under 110 \({}^{\circ}\)C. The activation products were denoted by AC500, AC600, and AC700. Carbonization yield (%) was calculated by dividing mass of carbonized bagasse with the initial mass of bagasse for carbonation, which was 2.29 \(\pm\) 0.02 g. Moreover, the activation yield (%) was calculated by dividing the dry mass of the activation result with the mass of carbonized bagasse.  
The dried bagasse was characterized by thermo gravimetric analysis (TGA, STA Linseis PT-1600) and scanning electron microscopy/energy dispersive X-ray (SEM/EDX, JEOL JSM 6510 LA) to investigate its surface morphology. The TGA analysis was conducted at 0-1000 \({}^{\circ}\)C with an increasing rate of 5 \({}^{\circ}\)C/min to study its thermal properties. The flask was vacuumed before heating. PXRD analysis was conducted (Rigaku Miniflex) using Cu/K\(\alpha\) radiation ranging from 0 to 80\({}^{\circ}\) to identify the characteristic peaks, phase content, and crystallinity of dried bagasse by comparison with standard diffraction of carbonaceous material. Fourier transform infrared (FTIR) analysis (Shimadzu IR Prestige-2) was done to analyze the presence of some specific functional groups. The surface area and porosity of the char and the prepared activated-carbon were analyzed using a surface area analyzer (Quantachrome Instruments, type Nova 1200e) through the measurements of adsorption and desorption of N\({}_{2}\) at 77K at a relative pressure.  
The carbon content was determined by taking 0.2 g of the carbonized bagasse and then dissolved it in 200 mL of 1M NaOH solution, by heating at 70 \({}^{\circ}\)C under continuous stirring for 30 min. The mixture was then stored overnight, followed by filtration. The residue was washed with 0.1 M HCl solution and followed by water leaching until the pH was 7. The neutralized-carbon was then dried at 80 \({}^{\circ}\)C for 12 h and then was gravimetrically weighted.  
Moreover, acidity of the activated-carbon was determined by ammonia adsorption. The ammonia adsorption test was conducted by placing a definite amount of the activated-carbon in a flacon that was kept in a desiccator along with 100 mL of ammonia solution. The desiccator was vacuumed and then cured for 24 h. The weight of the activated-carbon before and after ammonia adsorption was analyzed to calculate mg of NH\({}_{3}\) being adsorbed by a gram of the activated-carbon to determine the acidity value (mg/g).