Removal potential and mechanism of sulfamethoxazole and norfloxacin by biochar derived from bagasse and polymeric ferric sulfate

To evaluate the potential for practical application of biochar derived from bagasse and polymeric ferric sulfate (BPFSB), its capabilities and mechanisms for the removal of sulfamethoxazole (SMX) and norfloxacin (NOR) were explored. The optimized conditions were as follows: pH=2, dosage of 0.5 g L-1 (SMX); pH=6, dosage of 0.5 g L-1 (NOR). The maximum removal capacities of SMX were 266.8 (298 K), 265.9 (308 K) and 258.7 mg g-1 (318 K), while those of NOR were 197.7 ( 298 K), 198.8 (308 K) and 211.6 mg g-1 (318 K), respectively. Their spontaneous removals were dominated by multilayer surface chemisorption. However, the removal of SMX was exothermic (ΔH=-12.27 kJ mol-1) while the removal of NOR was endothermic (ΔH=13.84 kJ mol-1). Their removals followed pseudo-second-order kinetic model better, and liquid film diffusion was the primary rate-controlling step. The electrostatic interactions, H-bonding, complexation and π-π interactions were the main pathways of their chemisorption, while their degradation also contributed significantly to their removals. After five regenerations, the BPFSB was still effective in removing SMX (>85%), suggesting that it was more suitable for SMX removal in practice.