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 CaCl2 on 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-202 and MN-150

with the aid of hydrophobic effect

electrostatic interaction

H-bond and π-π electron-donor-acceptor interactions.