Abstract—A low-cost coffee-based activated carbon for Rhodamine B (RhB) removal was investigated. Spent coffee grounds obtained from a local coffee shop in Pathio, Chumphon, Thailand, were utilized as the raw material to produce biochar. The coffee grounds were pre-treated by washing with 1M H2_SO₄before carbonization at 600 ºC for 2 h under a limit-oxygen atmosphere. The acid washing process was found to be a promising method for preparing activated carbon without requiring an inert gas flow during the carbonization. This approach resulted in activated carbon free of ash after carbonization. The carbonized coffee grounds were activated using a microwave-assisted process with KOH as the activating agent. The performance of the prepared activated carbon for Rhodamine B adsorption was evaluated using the batch method. Key parameters, including initial concentration of Rhodamine B (3–11 mg/L), pH (3–11), and contact time (15–150 min), were optimized. The maximum adsorption capacity was 16 mg/g of adsorbents. The optimal pH for Rhodamine B adsorption was found to be 7. The adsorption of Rhodamine B onto the adsorbent fits a Langmuir isotherm and a pseudo-second-order kinetic model. The study revealed that the prepared activated carbon from waste coffee grounds is an efficient and affordable solution for removing Rhodamine B contaminants from the water system.

Keywords—activated carbon, Rhodamine B, KOH, limitoxygen carbonization, microwave activation, acid washing

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Cite: Kanchalar Keeratirawee, Orasa Choola-aied, and Pornprapa Kongtragoul, "Preparation of Low-Cost Activated Carbon from Spent Coffee Grounds for Rhodamine B Removal," International Journal of Environmental Science and Development vol. 16, no. 5, pp. 386-392, 2025.

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