Efficient Removal of Antibiotics from Aqueous Solutions through a Zn (II)–Norfloxacin Complex Formation on Porous Carbon from Sugar Cane Leaf Waste

Sustainable porous carbon adsorbents were developed from waste sugar cane leaves and tops (SC), while adsorption testing revealed that they are highly effective for the removal of antibiotics (norfloxacin and amoxicillin) from aqueous systems. Chemical activation of SC with ZnCl2, KOH, or H3PO4 led to superior surface area and adsorption capacity of the antibiotics at pH 7, compared to physical activation with nitrogen or carbon dioxide (SC-N2 and SC-CO2). ZnCl2-activated carbon (SC-ZnCl2) exhibited the highest surface area (548 m2 g–1) and greatest adsorption for norfloxacin (451 mg g–1) and amoxicillin (157 mg g–1) at pH 7. X-ray photoelectron spectroscopy analyses confirmed the presence of ZnO on the surface of the SC-ZnCl2 resulting from the activation process. Importantly, at pH 9, SC-ZnCl2 achieved an extraordinary norfloxacin adsorption capacity of 793 mg g–1, which could be attributed to the first reported formation of a Zn–norfloxacin complex on the surface of an activated carbon adsorbent. ZnCl2 activation is an efficient, low-cost method for producing high-performance carbons from sugar cane wastes, while ZnO incorporation plays a crucial role in the selective removal of norfloxacin at pH 9.