Air filtration performance of symmetric polypropylene hollow-fibre membranes for nanoparticle removal

This work aimed to determine filtration performance of polypropylene hollow-fibre membranes (HFMs) for removing submicron particles from air. Experiments were performed in a glass chamber supplied with a nanoaerosol particles formed by burning incense sticks. Three types of HFMs varying in packing density, active filtration area and pore-size distribution were tested in an outside-in configuration. By measuring the number of particles upstream and downstream of the HFM, the filtration efficiency was determined. Three permeate velocities (5, 10 and 15 cm/s) were used to compare the velocity effect on filtration efficiency. Particle counting was carried out using a TSI 3075 condensation particle counter connected to a TSI 3080 scanning mobility particle sizer in 48 particle size channels from 18.1 to 100 nm. The results show high efficiency, mostly higher than 99% for particles above 60 nm size. The most penetrating particle sizes (MPPS) were between 35.9 and 40 nm at 5 cm/s with an efficiency of 82-86%. At permeate velocity of 10 and 15 cm/s, MPPS slightly decreased to range of 34.6-40 nm, with efficiency decreasing to 72-84% and 69-83%, respectively. The quality factor of HFMs was within the 2-28 kPa(-1) range.