Environmental Chemistry Environmental Chemistry Society
Environmental problems - Chemical approaches

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An adsorption and thermodynamic study of ofloxacin on marine sediments

wenqing CAO , jun song , Guipeng Yang

Abstract

Abstract: The adsorption behavior of ofloxacin (OFL) on marine sediments treated with different methods were investigated using batch experiments. Three factors (sediment organic carbon content, salinity, and temperature) that might affect the adsorption behavior of OFL were analyzed. The equilibrium time of OFL adsorption on marine sediment in natural seawater was approximately 4−5 h. The adsorption of OFL on all sediments with different treatments fitted the Freundlich model well. Kf value was in the order of Kf (H2O2 treatment) < Kf (H2O treatment) < Kf (HCl treatment) over the studied concentration range. The adsorption of OFL was influenced not only by the sediment organic carbon content but also by external factors such as salinity of media and temperature. The adsorption was favorably influenced by the decreased salinity and temperature of seawater. The adsorption capacity of OFL on marine sediments decreased with the increase of temperature and salinity. The adsorption parameter Kf values decreased from 33.73 ± 1.66 (L/kg)1/n to 22.54 ± 1.12 (L/kg)1/n when the temperature increased from 283 K to 313 K. The changes of standard Gibbs free energy (ΔGθ) and enthalpy (ΔHθ) were −6.62 ± 0.34 kJ/mol (at 298 K) and −7.58 ± 0.38 kJ/mol, respectively, indicating that the adsorption process of OFL was spontaneous and exothermic. The positive value of the change of entropy ΔSθ (i.e., 3.38 ± 0.17 J K−1 mol−1) suggested that the degree of freedom increased during the adsorption process. Keywords: ofloxacin; marine sediments; adsorption isotherms; thermodynamics; media; temperature

EN16188  Accepted 29 July 2017

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