Removal of antibiotic Ciprofloxacin Hydrochloride from water by Kandira stone: Kinetic models and thermodynamic

In this study, Kandira stone, extensively used as a cladding material for building stone has been examined for the removal of an antibiotic Ciprofloxacin hydrochloride (CIP) from its aqueous solution. Batch experiments were performed to investigate the adsorption kinetics, equilibrium and thermodynamics between the adsorbent surfaces and CIP. The sorption data follows Freundlich isotherm. A chemical adsorption was dominant. The adsorption behaviour of CIP onto Kandira stone followed the pseudo-second-order kinetic model, indicating that the adsorption process can be expressed with the chemisorption mechanism. The intraparticle diffusion process is a rate-controlling step. The adsorption thermodynamic parameters of the free energy change (∆G^o), the isosteric enthalpy change (∆H^o) and the entropy change (∆S^o) were calculated. The negative ∆H^o values indicated that sorption of CIP was the exothermic process. The positive value of ∆G^o indicates non-spontaneous nature of CIP adsorption.