A spectroscopic and theoretical investigation of interaction mechanisms of tetracycline and polystyrene nanospheres under different conditions

Abstract Interaction mechanisms of tetracycline (TC, as a typical antibiotic) on polystyrene microsphere (PSs, as a typical nanoplastic) were conducted by the batch, spectroscopic and theoretical techniques. The batch results showed that Na + and K + had no obvious effects on TC adsorption towards PSs, whereas Mg 2+ significantly inhibited TC adsorption at pH > 5.0 due to its induced aggregations of PSs. The maximum TC adsorption capacity of PSs in the presence of humic acid (50.99 mg/g) was higher than that of PSs (44.77 mg/g) at pH 6.0. The highly effective adsorption was attributed to electrostatic attraction, π-π interaction and hydrophobic effect, which was determined by FT-IR and XPS analysis. According to DFT (density functional theory) calculations, the adsorption energy of TC/TC + on PSs (1.52 eV) was significantly higher than that of negative TC − (0.57 eV), whereas minimum distance of TC on PSs (3.684 A) was shorter than that of TC − on PSs (3.988 A). The results of theoretical calculations indicated that TC was more preferably adsorbed on PSs with more stable configuration compared to TC − . These findings indicated that PSs can be used as a promising adsorbent for immobilization and pre-concentration of TC from aqueous solutions.