Table 3.
Physicochemical parameters of MNPs and ecotoxicity (EC50 *, mg/L) of MNPs and humic acids (HA).
| Sample | %Fe3O4 | ξ, mV | Hydrodynamic Diameter, nm | 24 h EC50 for P. caudatum, mg/L | 96 h EC50 for S. alba, mg/L |
|---|---|---|---|---|---|
| Fe3O4 | 83 | −25.5 ± 6.03 | 400.8 | >33 ** | >3300 |
| HA | - | - | - | >33 ** | 900.65 ± 106.2 |
| Fe3O4/HA | 79 | −38.8 ± 7.1 | 153.2 | 32 ± 3.1 | 902.71 ± 211.5 |
| Fe3O4/HA harsh oxidation | 48 | −16.19 ± 2.1 | 886.7 | 0.33 ± 0.01 | 330 ± 10.1 |
| Fe3O4/HA mild oxidation | 0 * | −49.63 ± 2.2 | 586.1 | 1.40 ± 0.5 | 951.6 ± 80.2 |
* EC50 is the concentration of a sample reducing the root length or survival of ciliates by 50%; ** highest concentration that was tested; Color code: ≤1 mg/L (red )= very toxic; >1-10 mg/L (orange ) = toxic; >10–100 mg/L (yellow ) = harmful; >100 mg/L (green ) = “not classified/not harmful”. EC50 data not allowing ranking are on white background.