Dispersion and sedimentation of titanium dioxide nanoparticles in freshwater algae and daphnia aquatic culture media in the presence of arsenate

Figures & data

Table 1. Water chemistry analysis of algae and daphnia culture media.

Medium	TDS (mg/L)	Conductivity (μs/cm)	Ionic strength (mM)	pH
BG-11	1239 ± 6	1846 ± 23	23.44 ± 0.30	7.13 ± 0.30
SM7	419 ± 9	1619 ± 17	20.56 ± 0.20	7.76 ± 0.07

Figure 1. SEM images of TiO₂ nanoparticles dispersal in (a) ultrapure water, (b) BG-11, and (c) SM7.

Table 2. Hydrodynamic diameter (d_H), polydispersity index (PDI), zeta potential (ζ), and pH measurements of TiO₂ nanoparticles in culture media at a 20 ppm TiO₂ concentration.

Medium	dH (nm)	PdI	ζ (mV)	pH
Ultrapure water	206 ± 19	0.26	22.90 ± 0.15	6.96 ± 0.1
BG-11	544 ± 135	0.39	−10.90 ± 0.31	7.07 ± 0.3
SM7	605 ± 157	0.40	−0.71 ± 0.05	7.63 ± 0.3

Table 3. Zeta potential (ζ) and pH measurements of nTiO₂ at 20 ppm in culture media of different arsenate concentrations.

Culture media	As (uM)	ζ (mV)	pH
Ultrapure water	0	22.90 ± 0.15	6.41 ± 0 .02
	1	19.70 ± 0.21	6.84 ± 0.04
	10	11.23 ± 0.19	6.38 ± 0.01
	100	0.06 ± 0.00	7.27 ± 0.14
BG-11	0	−10.90 ± 0.30	7.16 ± 0.09
	1	−16.20 ± 0.17	7.31 ± 0.24
	10	−29.70 ± 0.09	6.82 ± 0.15
	100	−34.90 ± 0.37	7.39 ± 0.21
SM7	0	−0.71 ± 0.05	7.53 ± 0.06
	1	−4.90 ± 0.08	7.51 ± 0.07
	10	−15.20 ± 0.52	7.54 ± 0.1
	100	−29.70 ± 1.21	8.36 ± 0.07

Figure 2. TiO₂ agglomerate size as determined by DLS analysis, increasing with increasing TiO₂ nanoparticle concentration. Error bar: mean ± SD (n = 3). *denotes statistical differences from the control with p-values of P < 0.001.

Figure 3. Sedimentation of TiO₂ nanoparticles under different TiO₂ nanoparticle concentrations.

Figure 4. Effects of arsenate concentration on TiO₂ nanoparticles dispersion. nTiO₂ concentration was 20 ppm for all media. Error bar: mean ± SD (n = 3). *denotes statistical differences from the control with P-values of <0.001.

Figure 5. Sedimentation of TiO₂ nanoparticles under different arsenate concentrations. nTiO₂ concentration was 20 ppm for all media.