Tetracyclines Sorption in the Presence of Cadmium on River Sediments: the Effects of Sorption Mechanism and Complex Properties
2016
Chen, Zhenhe | Li, Guoao | Sun, Liquan | Li, Ye
Metal cations could enhance the sorption of tetracyclines but sometimes the effects are negligible. It is still not clear how these metals produce different effects. In this study, the sorption of chlortetracycline (CTC), tetracycline (TC), and oxytetracycline (OTC) was performed in the presence of Cd (II) to reveal the unknown mechanisms with two river sediments. It is found that Cd (II) could enhance the sorption of TCs on sediment SS, while it is negligible on sediment SY. For different tetracyclines, the enhancement effect by Cd (II) was more significant for CTC, while it is inferior for OTC and TC. Sorption isotherms of Cd (II) under strong and weak background electrolyte and pH decrease of sorption solutions indicate specific sorption is major on SY and cation exchange is significant on SS. Consequently, specific sorption is unfavorable for the enhanced sorption of TCs in the presence of Cd (II) because it is not favorable for the sorption of Cd-TCs by complexation and cation exchange. By the theoretical calculations, it is found that the significant enhancement of CTC is due to the higher electron affinity of Cd-CTC complex than the others to the surface groups. In conclusion, TCs sorption will not be affected by Cd (II) on sediments or soils with strong specific sorption characters of Cd (II).
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