Abstract：The kinetics characteristics and sorption amount under different pH conditions (i.e. pH=3.5, 5.0, 5.6 and 6.2) and the thermodynamics characteristics of norfloxacin (NOR) sorption on goethite (α-FeOOH) were determined by batch equilibrium experiments according to OECD Guideline 106 in this study. The sorption mechanisms were also found out. Results showed that the sorption of NOR on α-FeOOH began from a rapid stage with continuing for approximately 6 h, and then followed with a slow stage until a 48 h of sorption equilibrium time. Sorption kinetic curves fit a pseudo second-order kinetic model well at different pH. The sorption amount of different pH corresponded to the decreasing order of 5.6 > 5.0 > 6.2 > 3.5, which depended on the sum of the products concentrations obtained from different species of α-FeOOH and NOR at respective pH value. This result also indicated that the order of sorption amount was mostly attributed to the sorption of NORH2± on the surface of α-FeOOH. The Freundlich model could compatibly describe sorption isotherm of NOR on α-FeOOH. The 1/n of the isotherm fitted by the Freundlich model increased from 0.43 to 0.61 with increasing temperature from 15 ℃ to 35 ℃, which indicated that an increase in temperature could reduce the nonlinear sorption of NOR on α-FeOOH. Results with -39.45 kJ/mol of ΔH0 and less than 0 of ΔG0 revealed that the sorption of NOR on α-FeOOH was a spontaneously exothermic process. The exchange of ion was a dominant sorption mechanism for NOR sorption on α-FeOOH, while the H-bonding and dipole force were other possible sorption mechanisms. Less than 0 of ΔS0 indicated an entropy decrease during the sorption process.
