Generation of TiO₂ Aerosols from Liquid Suspensions: Influence of Colloid Characteristics

Figures & data

Figure 1 Scheme of the experimental setup (a) used for nanoparticle nebulization. The system generates liquid droplets with similar sizes for both pure water (b) and nanoparticle suspensions (c). Droplet size distributions were measured using an OPC without diffusion dryer in the range from 0.3 to 20 μm. (Color figure available online.)

Figure 2 XRD diffraction patterns of the TiO₂ and MWTiO₂ nanoparticles. Anatase and rutile peak positions are shown for identification purposes. (Color figure available online.)

Figure 3 SEM images of TiO₂ (a) and MWTiO₂ (b) nanoparticles.

Table 1 Particle sizes in the colloidal (measured by DLS) and in aerosol state (measured by SMPS) of TiO₂ and MWTiO₂ at different pH values

	MWTiO2			TiO2
pH	D^ah (nm)	GMD^b (nm)	GSD^c	D^ah (nm)	GMD^b (nm)	GSD^c
11	166	34.5   106	1.73   1.63	446	59.1	1.67
5	203	14.4   80.8	1.34   1.52	803	54.6	2.08
2	195	10.1   45.6	1.25   1.49	632	37.9	1.65

^aHydrodynamic diameter of particles in the suspension. The polydispersity index was always under 0.2 nm; ^bgeometric mean diameter of aerosol particles, determined from SMPS measurements; ^cgeometric standard deviation.

Figure 4 TEM images of TiO₂ (a, b) and MWTiO₂ (c, d) nanoparticles. Insets show size histograms for both nanoparticles (N > 100). (Color figure available online.)

Figure 5 Particle number total concentration (in #/cm³) of residual particles generated upon nebulization of water of different origins as function of the flow rate. (Color figure available online.)

Figure 6 Particle number total concentration (in #/cm³) generated at different flow rates from the nebulization of colloidal dispersions (1 mg/ml, pH 5) of TiO₂ and MWTiO₂ nanoparticles. Particle number concentration from the nebulization of milli-Q water are shown for the sake of comparison. (Color figure available online.)

Figure 7 Particle number size distributions (in #/cm³) obtained at different nebulization flow rates of TiO₂ (a) and MWTiO₂ (b) from colloidal dispersions of 1 mg/ml at pH 5. (Color figure available online.)

Figure 8 SEM images of TiO₂ (a, b) and MWTiO₂ (c, d) nanoparticles collected on a polycarbonate filter grid at 1.2 L/min. Insets show EDX analysis. (Color figure available online.)

Figure 9 Particle number size distributions (in #/cm³) of aerosols generated from the nebulization of colloidal dispersions of TiO₂ (a) and MWTiO₂ (b) at different pH values. (Color figure available online.)