Sorption of Antibacterial Compounds, Penicillin and Triclosan, to Clays: Implications for Removal of Pharmaceuticals from Aqueous Systems

The fate of antibacterial compounds is an important area of research due to the correlation between antibiotic contamination and the proliferation of antibiotic-resistant bacteria. Triclosan (TCS) is a common active antimicrobial agent in antibacterial hand soaps and other antimicrobial products. The effects of TCS contamination in the environment are not understood. TCS sorption to three clays (illite, kaolinite, and montmorillonite) was studied in batch experiments at various pH conditions and TCS concentrations. Preliminary results indicate that sorption of hydrophobic TCS does not follow adsorption trends of polar antibacterial compounds at near-neutral pH. Also, expansion of the clay crystal structure interlayer spacing (d-spacing) in montmorillonite (as detected by powder X-ray diffraction) suggests multiple TCS-clay sorption mechanisms. The sorption of Na-ampicillin (AMP) to clays was also investigated in batch mixing experiments at various pH conditions. AMP is a common penicillin-class human and veterinary antibiotic. Results yield non-linear isotherms as well as interlayer expansion and clay-enhanced degradation of AMP under certain conditions. Overall preliminary results of the ongoing study indicate an important and complex role for clays in the fate, transport, and removal of antibacterial compounds in sediment-water systems