诺氟沙星在胡敏酸上的吸附热力学与动力学特征研究

根据OECD Guideline106批平衡实验,研究了诺氟沙星在胡敏酸上的吸附热力学和动力学,并探讨了其可能吸附机理。结果表明,诺氟沙星在经过约12h的快速吸附阶段后,进入缓慢吸附阶段,其吸附平衡时间为48h。伪二级动力学方程能够较好地描述不同pH条件下诺氟沙星在胡敏酸上的吸附动力学特性。诺氟沙星在胡敏酸上的吸附等温线符合Freundlich方程,该方程的拟合系数1/n〈0.5,表明诺氟沙星在胡敏酸上为非线性吸附。ΔH0=-48.85kJ·mol-1和ΔG0〈0,表明诺氟沙星在胡敏酸上的吸附是自发进行的放热过程,且离子交换是其主要吸附机理,同时也可能存在着偶极间作用力、氢键力和电荷转移等吸附机理;ΔS0〈0表明吸附过程中熵在减小。吸附位点的能量随着吸附量的增大而降低,也表明胡敏酸的异质性和吸附的非线性。

Thermodynamics and Kinetics of Norfloxacin Sorption on Humic Acid

The thermodynamics and kinetics characteristics of norfloxacin（Nor） sorption on humic acid（HA） were investigated by batch equilibrium studies according to OECD Guideline 106,and the sorption mechanisms were also discussed in this study.Results showed that the sorption of Nor to HA began from a rapid stage with continuing for approximately 12 h,and then followed with a slow stage until a 48 h of sorption equilibrium time.Sorption kinetic curves at different pH were well fit with a pseudo second-order kinetic model.The Freundlich model could properly describe sorption isotherm.The sorption isotherm indicated nonlinear characteristics due to 1/n of isotherm fitted by the Freundlich model less than 0.5.Results with-48.85 kJ·mol-1 of ΔH0 and less than 0 of ΔG0 revealed that the sorption of Nor on HA was a spontaneously exothermic process.The exchange of ion was the dominating sorption mechanism for Nor sorption on HA,while the H-bonding and dipole force might be the other sorption mechanisms.Less than 0 of ΔS0 indicated an entropy decrease during the sorption process.Energy at sorption site decreased as the sorption amount increased,indicating the heterogeneity and non-linear sorption characteristic of HA.