Abstract:
Large-scale animal production has been responsible for the introduction of fluoroquinolones in the environment and the occurrence of adverse effects in non-target organisms. Under this scenario, this study evaluated the sorption of danofloxacin (DAN) in a Brazilian sandy (N1) and clay soil (S2) and in their isolated humic acids (HAs) and clays. The drug presented higher sorption on S2 with Freundlich coefficient pH-dependent ranging from 85 to 676 ?g1-1/n (mL)1/n g-1 on soils. Distribution coefficients (Kd) showed the order: humic acids > clays > soils for N1 and S2. The Kd of N1 HA (less humificated and richer in oxygenated groups) was higher than S2 HA, but S2 clay (with higher content of oxides of Fe and Al) sorbed more DAN than N1 clay. The DRX data pointed a sorption process restricted to the external surfaces of kaolinite. After the sorption of DAN, the FTIR of HAs presented a reduction of signals of COO-, C=O and OH- groups, suggesting the contribution of ionic interactions and hydrogen bonding for sorption. The cation exchange mechanism was supported by the dependence of the ionic strength and nature of the exchangeable cation for the sorption of DAN. Also, the FTIR of sorbed DAN on S2 clay indicated the contribution of Fe and Al oxides in additional interactions with the molecule. |
