Surface-collection efficiency of Nuclepore filters for nanoparticles

Figures & data

Table 1. Structural characteristics of Nuclepore filters, test conditions for collection efficiency, and minimum surface-collection efficiency.

	0.08 µm pore filter		0.2 µm pore filter		0.4 µm pore filter	0.8 µm pore filter		1 µm pore filter
Reference	This study		This study		Cyrs et al. (2010)	Cyrs et al. (2010)		Chen et al. (2013)
Pore diameter (µm)	0.059 ± 0.008		0.17 ± 0.01		0.29 ± 0.05	0.72 ± 0.18		1
Pore density (pores·cm^−2)	7.0 × 10^8		2.9 × 10^8		9.7 × 10^7	1.8 × 10^7		2 × 10^7
Porosity (%)	1.9		6.3		6.4	7.3		16
Thickness (µm)	6		10		10.6	10.5		11
Face velocity (cm·s^−1)	1.9	8.4	1.5	8.6	3.7	3.7	18.4	5
Pressure-drops (kPa)	6.3	25	2.3	12	2.4	0.8	4	0.8–1
Minimum surface collection efficiency	0.79 ± 0.17(30 nm PSL);0.61 ± 0.08(30 nm Ag)	0.72 ± 0.08 (30 nm PSL);0.69 ± 0.15 (20 nm Ag)	0.79 ± 0.08 (30 nm PSL);0.76 ± 0.15 (30 nm PSL)	0.60 ± 0.08 (30 nm PSL);0.64 ± 0.08 (30 nm Ag)	0.22 ± 0.08 (42–75 nm KCl)	0.27 ± 0.03 (42–75 nm KCl)	0.15 ± 0.02 (42 nm KCl)	0.3 (80 nm PSL)

Table 2. Pressure-drops of filters with and without filter support screen^aa.

		Pressure-drop [kPa]
	Flow rate[L·min^−1]	With screen	Without screen	Ratio [−]
0.08 μm pore filter	0.3	6.3 ± 0.7	4.6 ± 0.3	1.4 ± 0.15
	1.0	25 ± 1.6	13 ± 0.6	1.9 ± 0.13
0.2 μm pore filter	0.3	2.3 ± 0.1	2.1 ± 0.2	1.1 ± 0.06
	1.5	12 ± 0.7	9.4 ± 0.7	1.3 ± 0.05

^a Values are given as mean ± standard deviation (n = 10).

Figure 1. Schematic diagram of the experimental setup.

Figure 2. Schematic diagram of portions of the filter sample used for SEM observation.

Figure 3. SEM images of (a) 30 nm Ag particles collected on the 0.2 μm pore filter and (b) 30 nm PSL particles collected on the 0.08 μm pore filter.

Figure 4. Collection efficiency due to interception in terms of N_r for each flow assumption.

Table 3. Results of experimentally measured surface collection efficiency^aa.

			0.08 µm pore filter		0.2 µm pore filter
	Particle diameter(nm)	Region of filter	Face velocity = 1.9 cm·s^−1	Face velocity = 8.4 cm·s^−1	Face velocity = 1.5 cm·s^−1	Face velocity = 8.6 cm·s^−1
Ag	15	Center (n = 3)	0.92 ± 0.04	0.81 ± 0.18	0.77 ± 0.06	0.66 ± 0.11
		Surroundings (n = 6)	0.82 ± 0.26	0.77 ± 0.18	0.83 ± 0.15	0.76 ± 0.09
		All (n = 9)	0.85 ± 0.21	0.79 ± 0.17	0.81 ± 0.12	0.73 ± 0.11
Ag	20	Center (n = 3)	0.68 ± 0.05	0.71 ± 0.07	—	—
		Surroundings (n = 6)	0.66 ± 0.13	0.68 ± 0.18	—	—
		All (n = 9)	0.67 ± 0.11	0.69 ± 0.15	—	—
Ag	30	Center (n = 3)	0.60 ± 0.06	0.70 ± 0.22	0.67 ± 0.22	0.65 ± 0.10
		Surroundings (n = 6)	0.62 ± 0.10	0.70 ± 0.10	0.80 ± 0.10	0.64 ± 0.07
		All (n = 9)	0.61 ± 0.08	0.70 ± 0.14	0.76 ± 0.15	0.64 ± 0.08
PSL	30	Center (n = 3)	0.67 ± 0.13	0.80 ± 0.05	0.77 ± 0.08	0.64 ± 0.02
		Surroundings (n = 6)	0.85 ± 0.15	0.67 ± 0.05	0.80 ± 0.09	0.58 ± 0.09
		All (n = 9)	0.79 ± 0.17	0.72 ± 0.08	0.79 ± 0.08	0.60 ± 0.08
PSL	50	Center (n = 3)	0.84 ± 0.09	0.99 ± 0.11	0.78 ± 0.06	0.59 ± 0.12
		Surroundings (n = 6)	0.89 ± 0.22	0.83 ± 0.16	0.83 ± 0.04	0.69 ± 0.07
		All (n = 9)	0.87 ± 0.19	0.89 ± 0.16	0.81 ± 0.05	0.66 ± 0.10
PSL	100	Center (n = 3)	1.07 ± 0.12	1.14 ± 0.13	0.82 ± 0.05	0.67 ± 0.08
		Surroundings (n = 6)	1.06 ± 0.07	0.93 ± 0.06	0.84 ± 0.07	0.74 ± 0.04
		All (n = 9)	1.06 ± 0.09	1.00 ± 0.13	0.83 ± 0.06	0.71 ± 0.06
PSL	300	Center (n = 3)	1.01 ± 0.16	1.02 ± 0.06	1.11 ± 0.03	1.11 ± 0.17
		Surroundings (n = 6)	1.00 ± 0.13	1.07 ± 0.10	1.07 ± 0.07	1.11 ± 0.12
		All (n = 9)	1.01 ± 0.13	1.06 ± 0.09	1.08 ± 0.06	1.11 ± 0.13
PSL	800	Center (n = 3)	1.01 ± 0.15	1.11 ± 0.04	—	1.13 ± 0.04
		Surroundings (n = 6)	0.98 ± 0.15	1.11 ± 0.07	—	1.09 ± 0.08
		All (n = 9)	0.99 ± 0.14	1.11 ± 0.06	—	1.10 ± 0.07

^a Values are given as mean ± standard deviation.

Figure 5. Surface-collection efficiency of the 0.08 μm pore filter at a face velocity of 1.9 cm·s⁻¹ (n = 9; shown as mean ± standard deviation).

Figure 6. Surface-collection efficiency of the 0.08 μm pore filter at a face velocity of 8.4 cm·s⁻¹ (n = 9; shown as mean ± standard deviation).

Figure 7. Surface-collection efficiency of the 0.2 μm pore filter at a face velocity of 1.5 cm·s⁻¹ (n = 9; shown as mean ± standard deviation).

Figure 8. Surface collection efficiency of the 0.2 μm pore filter at a face velocity of 8.6 cm·s⁻¹ (n = 9; shown as mean ± standard deviation).

Figure 9. Trajectories for particles with different Stokes number approaching a Nuclepore filter.

Cyrs, W. D., Boysen, D. A., Casuccio, G., Lersch, T., and Peters, T. M. (2010). Nanoparticle Collection Efficiency of Capillary Pore Membrane Filters. J. Aerosol Sci., 41:655–664.

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Chen, S. C., Wang, J., Fissan, H., and Pui, D. Y. H. (2013). Use of Nuclepore Filters for Ambient and Workplace Nanoparticle Exposure Assessment–Spherical Particles. Atmos. Environ., 77:385–393.

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