%0 Journal Article
%T Sorption of Tetracycline, Oxytetracycline, and Chlortetracycline in Illite and Kaolinite Suspensions
%A O. P. Bansal
%J ISRN Environmental Chemistry
%D 2013
%R 10.1155/2013/694681
%X The sorption interaction of three widely used tetracycline antibiotics, namely, tetracycline, chlortetracycline, and oxytetracycline, under various conditions of time, pH, temperature, ionic strength, and exchangeable cations on illites and kaolinites was examined. First-order reaction indicated diffusion-controlled adsorption, maximum adsorption occurring at pH values of 3.5, 3, and 4 for tetracycline, oxytetracycline, and chlortetracycline, respectively. Adsorption isotherms of ¡°L¡± type showed that the adsorption of antibiotics was in the order of chlortetracycline > oxytetracycline > tetracycline. Adsorption was maximum for Al-saturated complexes and followed the order of Al- > Na- > K- Ca. The adsorption varied inversely with changes in temperature and ionic strength up to 0.6 after which it became constant. Free energy changes (¦¤G) were negative signifying a spontaneous reaction; the values of ¦¤G suggest a partial physical adsorption. Enthalpy changes showed that the process is exothermic. The positive values of entropy change suggest that adsorption of tetracyclines molecules is in disordered arrangement on clay surfaces. The data of these parameters with IR and X-ray studies revealed the existence of protonation and/or coordination between exchangeable cation and oxygen of >C=O group of antibiotics. The amount of cations desorbed indicated that cation exchange phenomena played an important role during adsorption. 1. Introduction The use of antibiotics as veterinary pharmaceuticals has become the integral part of the animal food industry because of their valuable contributions in treating diseases [1], as growth promoters [2], and in improving feed efficiency [3]. The tetracyclines (tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC)) are broad spectrum antibiotics widely used in animal food industry. Tetracyclines contribute approximately 50% of total antibiotics production. Antibiotics may appear in the environment when manure, sewage sludge, and wastewater effluents are used up in different agricultural applications. Thus, a genuine concern arises that residual concentration of antibiotics in agricultural soils may lead to the development of bacterial resistance which may disperse in the environment or, alternatively, highly mobile antibiotics will accumulate in the soil and leach into groundwater. So, efforts towards their removal from wastewater and manure have been stimulated. Parolo et al. [4] found that Patagonian montmorillonite appeared as a good adsorbent of TC. Barbooti et al. [5] reported that Iraqi montmorillonite
%U http://www.hindawi.com/journals/isrn.environmental.chemistry/2013/694681/