Adsorption of Sulfamethoxazole on to Microwave-Activated Biochar

Antibiotics are widely used in human and veterinary medicine for disease prevention and treatment. However, a considerable portion of the administered doses are not metabolized or assimilated by animal or human bodies and are subsequently excreted in their urine and feces. In addition, antibiotics, as well as many pharmaceuticals, cannot be adequately degraded in wastewater treatment plants (WWTPs), given plant processes are typically designed to treat only easily and moderately biodegradable organics. Sulfamethoxazole (SMX) has been reported as the most often observed sulfonamide antibiotic in effluents of WWTPs. The current research aimed to prepare an agricultural residue-based biochar for the adsorption of SMX from water. Phosphoric acid (H₃PO₄) was used for biochar preparation as it is an efficient microwave activator. The activated biochar had a BET surface area of 1452 m²/g and showed a high SMX adsorption capacity of 181 mg/g. The adsorption site energy and its distribution based on the Freundlich model were estimated to describe the adsorption mechanism. The SMX molecules initially occupied the high-energy interlayer of the biochar before spreading to the low-energy active sites. Overall, the results indicated that microwave pyrolysis is an efficient method for creating an activating biochar adsorbent for removing SMX from water.