Valorization of Indonesian Cassava (Manihot esculenta) Stem Waste into Activated Carbon for Efficient Antibiotic Removal from Aqueous Media

Antibiotics are frequently detected in aquatic environments due to incomplete removal in conventional wastewater treatment plants, contributing to the spread of antimicrobial resistance and ecological risks. However, the widespread application of commercial activated carbon for antibiotic removal is limited by its high cost and reliance on non-renewable precursors, creating a need for low-cost, sustainable adsorbents derived from abundant agricultural wastes such as cassava stems (Manihot esculenta). In this work, cassava stem waste from Indonesia was converted into hydrochar via hydrothermal carbonization and subsequently activated by thermal treatment to produce cassava stem-derived activated carbon (CS-AHC). The materials were systematically characterized by XRD, FTIR, Raman spectroscopy, and SEM-EDS, and their adsorption performance toward selected antibiotics in aqueous solution was evaluated through batch experiments. The optimized CS-AHC exhibits a hierarchically porous structure with increased surface area, enhanced graphitic domains, and abundant oxygen-containing functional groups originating from the cassava stem precursor and activation process. These structural and chemical features provide a high density of accessible adsorption sites and favorable interactions with antibiotic molecules, enabling efficient removal from water while valorizing a locally abundant agricultural residue.