Oxytetracycline Adsorption on Iron Oxides: A Comprehensive Approach.

Oxytetracycline (OTC) is an important veterinary antibiotic.  Environmental fate of oxytetracycline has been directly linked to its adsorption on common iron oxides.  Here we report a comprehensive approach of studying the interactions of OTC with magnetite, goethite, and hematite.  Macroscopic adsorption isotherms, kinetics, and pH envelope experiments were coupled with surface complexation modeling (SCM) and in situATR-FTIR spectroscopic techniques to identify the molecular level information.  Spectroscopic results indicated that OTC formed inner-sphere type surface complex with magnetite, goethite, and hematite. However, increasing concentration or loadings had different effects on magnetite compared to goethite and hematite.  For magnetite, SCM modeling suggested that four complex ligand exchange reactions controlled the adsorption of OTC on magnetite.  Ongoing work is focusing on the surface interactions of OTC with mixtures of these iron oxides.