Table 2 Growth test with Pseudokirchneriella subcapitata – different dispersion methods and corresponding EC20 values (growth rate) with confidence intervals for the smaller TiO2 nanoparticles
Treatments for dispersion preparation | |||||
|---|---|---|---|---|---|
Stirring | Ultrasonication | Growth rate EC20 [mg/L] | 95 % confidence interval | Specific surface area [m2/g] | d(0.10) [µm] |
Experiment A: wide variation of stirring and ultrasonication | |||||
1 min | 15 min | 16.1 | 14.0–18.6 | 3.7 | 0.87 |
15 min | – | 10.6 | 6.6–16.3 | 3.0 | 1.13 |
1 d | – | 22.7 | 20.0–25.3 | 2.9 | 1.14 |
3 d | 15 min | 4.3 | 3.7–4.9 | 3.9 | 0.82 |
7 d | – | No toxicity | – | 2.9 | 1.05 |
Experiment B: fixed stirring period, variation of ultrasonication | |||||
1 min | 1 min | 46.0 | 34.4–65.3 | 3.6 | 0.87 |
1 min | 3 min | 25.5 | 11.8–57.6 | 3.7 | 0.85 |
1 min | 7 min | 22.2 | 16.0–29.4 | 3.3 | 0.92 |
1 min | 15 min | 27.2 | 18.2–40.6 | 3.8 | 0.85 |
Experiment C: variation of stirring, fixed ultrasonication period | |||||
1 min | 3 min | 6.9 | 2.8–11.4 | 3.7 | 0.85 |
3 min | 3 min | 8.9 | 2.8–16.3 | 3.7 | 0.83 |
7 min | 3 min | 4.0 | 2.0–6.3 | 3.6 | 0.82 |
15 min | 3 min | 0.8 | 0.1–2.4 | 3.7 | 0.82 |