Abstract: The low-cost calcium-based bentonite modified by anionic and cationic surfactants was granulated and a particulate adsorbent was prepared by response surface optimization. The dynamic adsorption behavior of norfloxacin (NOR) in water was studied in a downflow fixed bed column. The effects of the contact time of empty bed, the height of the bed and pH value of the solution influent on the adsorption process were investigated. Considering the economy and high efficiency of the practical application, the optimal operating conditions of the adsorption column were selected in the experiment. The initial concentration of NOR was 2 mg·L^-1, the solution pH was 3, the contact time of empty bed (EBCT) was 20 min, the bed height (H) was 15 cm, and the flow rate (Q) was 1.33 mL·min^-1. The experimental results show that the removal rate of NOR can reach to more than 70% under these conditions. And the penetration time of NOR by the modified bentonite particles (C/S-Mt) was increased by 270 min. The maximum adsorption amount(q_t) increased by about 910 μg while the equilibrium adsorption amount was about 330 μg·g^-1 higher than the unmodified native soil particles (Ca-Mt). The performance of bed column was estimated by Thomas and Yoon-Nelson models. The analysis indicate that the two models can accurately predict the adsorption quantity and the breakthrough curves, respectively.

Key words: bentonite particles, norfloxacin, fixed bed column, dynamic adsorption