Effective Use of Sugarcane-Bagasse-Derived KOH-Activated Biochar for Remediating Norfloxacin-Contaminated Water

Bagasse-derived biochar (SCB₇₅₀) was prepared at 750 °C using Chinese sugarcane bagasse as a carbon source and then modified with KOH for the removal of the antibiotic norfloxacin (NOR) from aqueous solutions. 3K-SCB₇₅₀, prepared using a solid-to-liquid mass ratio of bagasse:KOH = 1:3, was found to have the best adsorption performance for NOR. Under the conditions of pH 5, 25 °C, 2.4 g L⁻¹ adsorbent, and 300 mg L⁻¹ NOR, its adsorption of NOR reached equilibrium (97.5% removal) after 60 min. The adsorption behaviours were in line with the quasi-second-order kinetic and Langmuir isotherm models, respectively. The maximum theoretical adsorption capacity reached up to 157.4 mg·g⁻¹ at 40 °C. The thermodynamic parameters showed that the adsorption of NOR onto 3K-SCB₇₅₀ was a spontaneous, endothermic, and physical process. In addition, Brunauer−Emmett−Teller analysis (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy were conducted to investigate the structural and adsorption properties of 3K-SCB₇₅₀. Fourier transform infrared spectroscopy (FTIR) was also applied to understand the mechanism of adsorption of NOR onto 3K-SCB₇₅₀. All of the results indicated that 3K-SCB₇₅₀ had a large specific surface area of 1038.8 m²·g⁻¹, an average pore size of 1.9 nm, and hierarchical structures with random pores and cracks for efficient removal of NOR. NOR adsorption mechanisms on 3K-SCB₇₅₀ were related to the pore-filling effect and electrostatic attraction. Therefore, 3K-SCB₇₅₀ biochar may be used as a promising adsorbent of antibiotics in wastewaters.