Efficient with low-cost removal and adsorption mechanisms of norfloxacin, ciprofloxacin and ofloxacin on modified thermal kaolin: experimental and theoretical studies.

Quinolone antibiotics (QNs) can be potential hazard to environment and human. Combination of experimental and theoretical studies was used to analyze the adsorption properties of norfloxacin, ciprofloxacin and ofloxacin on modified thermally activated kaolin (KL). Main factors (calcination temperature, dose, pH, cations and regeneration) affecting the adsorption were discussed. Adsorption processes fit the pseudo-second order kinetic and Langmuir model well. The adsorption removal of norfloxacin, ciprofloxacin and ofloxacin can reach 88.53%, 89.43% and 91.46%, respectively. Cations inhibited adsorption, and AlS-KLB can maintain 80% efficiency in five cycles under optimal conditions. Simulations showed that the materials had good adsorption capacity for QNs, and the "①" of KL had the best capacity. Simulations explain the adsorption mechanism: F, H, O atoms of QNs are covalently bonded to O atoms from KL, AlO and Al (OH), C atoms from amorphous carbon and H atoms from C-H and Al (OH). The Al atoms of AlO and Al, Si atoms of KL are ionically bonded to F, H, O atoms of QNs. This study shed new light on the removal of QNs by providing low-cost and efficient modified KL and elucidating the adsorption mechanism in conjunction with DFT simulations.