INTERACTIONS BETWEEN TETRACYCLINE AND KAOLINITE IN AQUEOUS SOLUTION

Tetracycline (TC) is a pharmaceutical antibiotic used for the treatment of bacterial infections in humans and animals, such as urinary tract infections and acne. When ingested, TC is not completely metabolized by the digestive tract, thus, it is excreted in high concentrations. This threatens to contaminate soil and water systems. It is known that clays have a high sorption capacity and can potentially remove contaminants from ground water. This study aimed to determine the reaction rate of kaolinite (KGA 1b) and sorption of TC in waters under specific conditions including varying concentration, pH, ionic strength, and temperature.

The results of this study indicate that the TC adsorption capacity was reached within 24 hours at 9 mmol/g on kaolinite, with the sorption being instantaneous and primarily on the external surfaces of kaolinite. An increase in pH decreased the sorption of TC slightly before pH reached the pK_a2 and drastically at pH values above the pK_a2 value of TC. Higher ionic strength also slightly reduced TC sorption. Increasing the temperature had little effect on the sorption of TC, with the exception of values near pH 8, where increasing the temperature decreased the amount TC sorbed. The balance between TC sorbed and metal cations desorbed suggests that cation exchange is responsible for TC sorption. Results from this study will provide a better understanding of TC transport in subsurface soils predominated by kaolinite and possible remediation strategies.