A spectroscopic and theoretical investigation of interaction mechanisms of tetracycline and polystyrene nanospheres under different conditions
2019
Wan, Tian | Lu, Songhua | Cheng, Wen | Ren, Jiehui | Wang, Min | Hu, Baowei | Jia, Ziyi | Li, Ying | Sun, Yubing
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 Mg2+ 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 Å) was shorter than that of TC− on PSs (3.988 Å). 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.
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