Adsorption kinetics of the antibiotic ciprofloxacin on bentonite, activated carbon, zeolite, and pumice

This study analyzes ciprofloxacin (CIP) sorption by bentonite, activated carbon, zeolite, and pumice, which have been recently considered for their potential use in the adsorption of specific pollutants. Batch experiments were performed to investigate the adsorption kinetics between the adsorbents surfaces and CIP. Adsorption kinetics for adsorbents were well described by the pseudo-second kinetic model. The amount of CIP adsorbed by the adsorbents at equilibrium showed the following sequence: bentonite > activated carbon > zeolite > pumice. The adsorption thermodynamic parameters of the free energy change, the isosteric enthalpy change, and the entropy change for 22(degrees)C were calculated. Thermodynamic of CIP adsorption shows that adsorption is the endothermic adsorption. The negative values of Delta G degrees for bentonite and activated carbon indicate the spontaneous nature of the adsorption. The positive value of Delta G degrees for zeolite and pumice indicates nonspontaneous nature of CIP adsorption. The positive entropy change indicated that the adsorption process was aided by increased randomness.