Abstract
In this study equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The Kd parameter from Linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin–Radushkevich (D–R) sorption models were applied to describe the equilibrium isotherms by linear and non-linear method.
The estimated Kd values ranging from 171 to 37347 mL/g indicate a very high sorption of ciprofloxacin on all investigated sediments. The obtained values of E were found to be from 3.51 to 8.64 kJ/mol for all experiments …show more content…
Due to fluoroquinolones limited metabolism in animal body, they are eliminated mainly as parent compounds (Pereira Leal et al., 2012; Turiel et al., 2006). In addition, they are move rapidly from the water compartment into solids (Picó and Andreu, 2007), mainly because their lipophilicity (log Kow = -1.00 to 1.60 (Thiele-Bruhn, 2003)), sorption coefficient (Kd=260 to 5612 L/kg (Thiele-Bruhn, 2003)) and carbon-normalized sorption coefficient which are responsible for their strong sorption onto solid samples. According to that, their concentrations up to 5770 ng/g were found in the sediments of three rivers in northern China (Zhou et al., …show more content…
Mechanisms such as surface complexation with metal ions (Ca2+, Mg2+, Cu2+, Fe3+ or Al3+), H-bonding, cation bridging, ion-exchange, and hydrophobic partition could affect onto sorption of pharmaceuticals (Tolls, 2001; Pereira Leal et al., 2013). But, their sorption varies greatly with soil or sediment physico-chemical properties; especially solid pH, quantity and quality of organic matter, and the types of minerals present (Thiele-Bruhn, 2003; Pereira Leal et al., 2013]. Except these, the sorption and the consequent accumulation of pharmaceuticals in solid matrices are firmly governed by the ionization property of numerous pharmaceuticals with the pKa values within an environmentally significant pH range (Hörsing et al., 2011). The sorption of pharmaceuticals onto solid matrices is not only influenced by their pH values but also by the ionic strength (Thiele-Bruhn, 2003). For example, the distribution coefficient Kd for enrofloxacin has been reported to vary by a factor of 30 (Boxall et al., 2004; Pereira Leal et al., 2013) which is a confirmation that is extremely important to understand the behaviour of these compounds under different environmental conditions (Pereira Leal et al., 2013). Because of that, and especially for the fact that the Kd value varies depending on the organic carbon content, it is recommended to use the organic
In this study equilibrium isotherms, kinetics and thermodynamics of ciprofloxacin on seven sediments in a batch sorption process were examined. The effects of contact time, initial ciprofloxacin concentration, temperature and ionic strength on the sorption process were studied. The Kd parameter from Linear sorption model was determined by linear regression analysis, while the Freundlich and Dubinin–Radushkevich (D–R) sorption models were applied to describe the equilibrium isotherms by linear and non-linear method.
The estimated Kd values ranging from 171 to 37347 mL/g indicate a very high sorption of ciprofloxacin on all investigated sediments. The obtained values of E were found to be from 3.51 to 8.64 kJ/mol for all experiments …show more content…
Due to fluoroquinolones limited metabolism in animal body, they are eliminated mainly as parent compounds (Pereira Leal et al., 2012; Turiel et al., 2006). In addition, they are move rapidly from the water compartment into solids (Picó and Andreu, 2007), mainly because their lipophilicity (log Kow = -1.00 to 1.60 (Thiele-Bruhn, 2003)), sorption coefficient (Kd=260 to 5612 L/kg (Thiele-Bruhn, 2003)) and carbon-normalized sorption coefficient which are responsible for their strong sorption onto solid samples. According to that, their concentrations up to 5770 ng/g were found in the sediments of three rivers in northern China (Zhou et al., …show more content…
Mechanisms such as surface complexation with metal ions (Ca2+, Mg2+, Cu2+, Fe3+ or Al3+), H-bonding, cation bridging, ion-exchange, and hydrophobic partition could affect onto sorption of pharmaceuticals (Tolls, 2001; Pereira Leal et al., 2013). But, their sorption varies greatly with soil or sediment physico-chemical properties; especially solid pH, quantity and quality of organic matter, and the types of minerals present (Thiele-Bruhn, 2003; Pereira Leal et al., 2013]. Except these, the sorption and the consequent accumulation of pharmaceuticals in solid matrices are firmly governed by the ionization property of numerous pharmaceuticals with the pKa values within an environmentally significant pH range (Hörsing et al., 2011). The sorption of pharmaceuticals onto solid matrices is not only influenced by their pH values but also by the ionic strength (Thiele-Bruhn, 2003). For example, the distribution coefficient Kd for enrofloxacin has been reported to vary by a factor of 30 (Boxall et al., 2004; Pereira Leal et al., 2013) which is a confirmation that is extremely important to understand the behaviour of these compounds under different environmental conditions (Pereira Leal et al., 2013). Because of that, and especially for the fact that the Kd value varies depending on the organic carbon content, it is recommended to use the organic