Adsorption Interaction of Tetracyclines with Porous Synthetic Resins

The presence of tetracycline antibiotics (TCs) in aquatic environments poses potential risks to human health and ecosystems. In the present study, hypercrosslinked resins MN-200 and NDA-150 and aminated polystyrene resins MN-150 and MN-100 were selected as adsorbents for removing two tetracyclines, TC and oxytetracycline, OTC, from aqueous solutions. Despite the different surface properties and pore structures of the resins, similar patterns of pH-dependent adsorption were observed. The TCs adsorption on the resins exhibited ionic strength dependence, which is consistent with their adsorption mechanism. OTC presented stronger adsorption at pH 2.0 compared with TC; this is ascribed to the enhancement by H-bonding. The proposed mechanisms for TCs adsorption at lower pH are dependent on H-bonding, hydrophobic effect, and π–π electron donor–acceptor (EDA) interaction, whereas those at higher pH are regarded as the coordination of π–π EDA interaction and hydrophobic effect. The findings indicate that the hypercrosslinked resin is a promising adsorbent for the removal of antibiotics from aqueous solutions.