Microwave-assisted activation is a green technology technique that can synthesize activated carbon from bagasse. In this study, microwave-assisted ZnCl₂ chemical activation was applied to convert bagasse to activated carbon (BAC). Activating activated carbon was optimized using surface response methodology (RSM). The Box-Behnken (BBD) design was used to assist in the optimum synthesis condition, with the loading of ZnCl₂ concentration (A: 10–50% w/v), heating time (B: 2–12 min), and microwave power (C: 150–800 W). The BAC was characterized using Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FT-IR), and moisture content. The findings of the BAC optimization were at a ZnCl₂ concentration of 24.281 (% w/v), 12 min of heating time, and 800 W of microwave power. The characterization result shows that BAC_op has mesoporous carbon and a desirable surface area of 446.874 m²/g, average pore size of 4.071 nm, pore volume of 0.054 cc/g, and total pore volume of 0.2531 cc/g. SEM analysis revealed that microwave-generated pore structures lead to the ZnCl₂ activation process. The pore structures of the raw material and activated carbon were different. The FT-IR analysis shows the existence of functional groups as well as changes in functional groups from raw material to activated carbon. The moisture content study findings are 5.51 to 9.21% in accordance with the Indonesian National Standard (SNI) 06-3730-1995. The isothermal adsorption-desorption process is classified as type IV adsorption with hysteresis loop H4, suggesting that the pore distribution in activated carbon is mesoporous with a tiny pore width and slit-shape pore materials.

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