Anionic surfactant-mediated transport of tetracycline antibiotics with different molecular structures in saturated porous media

Tetracyclines (TCs), a class of antibiotics that are most widely used veterinary and human medicine, possessed an ability to produce irreversible damage towards humans and environment. Antibiotics transport and deposition are critical processes in their environmental fate. In this study, the mobility properties of various TCs such as oxytetracycline (OTC), chlortetracycline (CTC) and tetracycline (TC), in quartz sand columns with sodium dodecylsulfate (SDS), a typical anionic surface-active agent over the pH array of 5.0 similar to 9.0 were investigated. The mobility of TCs through the column was in the order: OTC > TC > CTC. The difference in the molecular structures of various TC antibiotics could explain the trend. Interestingly, SDS enhanced TC transport via deposition site competition between surfactant and TC molecules, increased electrostatic interaction, and steric hindrance. SDS, on the other hand, inhibited OTC and CTC mobility primarily owing to the strong aquaphobic collaboration between antibiotics and the absorbed surfactant on the sand surface (i.e., SDS molecules as bridge agents between antibiotics and sand grains). Furthermore, at higher pH conditions (5.0 similar to 9.0), the enhanced or inhibitory effect of surfactant on the mobility of TCs declined. The observed decrease in the steric hindrance effect, competitive deposition, or hydrophobic interaction was attributed to the decreased deposition of SDS. Innovative information obtained from this work provides insight into the important role of an anionic surfactant on the mobility and deposition of various tetracycline antibiotics in aquifers. (C) 2022 Elsevier B.V. All rights reserved.