多孔树脂及碳纳米管对环丙沙星的吸附行为与机理

Adsorption behavior and mechanism of ciprofloxacin onto porous resins and carbon nanotube

以环丙沙星为研究对象,研究了多孔树脂(超高交联树脂MN-202,氨基修饰树脂MN-150,大孔树脂XAD-4)和多壁羧基碳纳米管C-MWCNT对环丙沙星的吸附行为和机理。结果表明:吸附剂的吸附量随溶液pH值的升高呈先增加后减小的变化趋势。3种树脂的吸附能力随溶液离子强度的增强而提高,而碳纳米管则呈相反趋势,这是因为疏水作用和静电引力对两类吸附剂的贡献不同。环丙沙星在4种吸附剂上的吸附动力学都符合准二级动力学模型,吸附等温线符合Langmuir模型。升高温度可以增强MN-202和MN-150的吸附能力,可能是微孔填充受温度影响;温度对XAD-4吸附能力的负相关作用是由于疏水作用,是主要吸附机理。对于C-MWCNT,温度对它的影响很小,这是由于疏水作用、静电作用、π-π键和氢键的共同作用。

Porous resins（hypercrosslinked resin MN-202,aminated polystyrene resin MN-150,and macroporous resin XAD-4）and carboxylated multiwall carbon nanotube C-MWCNT were used to remove ciprofloxacin from aqueous solutions.Similar patterns of pH-dependent adsorption show that the adsorption amounts of ciprofloxacin increase with the increase of their percentages of zwitterionic form,implying the importance of zwitterionic form.Ciprofloxacin adsorption to the three resins exhibits similar ionic strength dependence,consistent with the positive contribution of hydrophobic effect and the negative contribution of electrostatic interaction.The amounts of ciprofloxacin adsorbed decrease much more in the presence of CaCl2on the surface of C-MWCNT than with NaCl because of the dominant contribution of electrostatic interaction.The adsorption kinetics of the four adsorbents follow the pseudo-second order model while the adsorption isotherm data fit well to the Langmuir models,indicating the coverage of the surface by a mono-molecular layer.The apparent temperature influence on the adsorption process demonstrates that hydrophobic effect is dominant mechanism responsible for ciprofloxacin removal by XAD-4,while micropore-filling is likely the main mechanism for the adsorption by MN-202and MN-150,with the aid of hydrophobic effect,electrostatic interaction,H-bond andπ-πelectron-donor-acceptor interactions.