Abstract
Airborne particulate matter (PM) is causing more and more serious air pollution and threatening the public health. However, existing air filter technologies with the easy-to-block manner can rarely meet the requirements of high-performance PM filters. Here we propose a conceptually new type of inertial impaction filters for rapidly high-efficiency PM removal. Under the airflow velocity of 8.0 m/s, the real inertial impaction filters show high PM removal efficiencies of up to 97.77 ± 1.53% and 99.47 ± 0.45% for PM2.5 and PM10, respectively. Compared with the traditional air filters reported previously, the inertia impaction filters exhibit extremely low pressure drop of 5–10 Pa and high quality factor (QF) values of 0.380 Pa−1 and 0.524 Pa−1 for PM2.5 and PM10, respectively. These greatly improved QF values are achieved through a series of inertial separation processes. The feature dimension of filtration channel is dozens of times larger than PM average size, which greatly decreases airflow resistance. Particularly, this inertial structure can be made of various types of materials, which shows great potential for low-cost fabrication of large-area devices. As a stand-alone device or incorporated with the existing PM air filter, this inertial impaction filter will bring great benefits to the public health.
Highlights
Air pollutions have raised serious concerns for the public health[1]
Another type of air filter is a porous membrane filter based on size exclusion filtration, which is similar to a water filter, as shown in Fig. 1(b) (II)
In order to resolve this contradiction fundamentally, here we demonstrate a conceptually new type of air filter for particulate matter (PM) removal, which can work at high air flux with extremely low pressure drop
Summary
According to the second law of Newton, the trajectory of a PM particle obeys the process that a particle mass multiplied by acceleration equals to the force exerted on it. In order to precisely describe the trajectories of incident particles, we calculate the instantaneous velocity (u, v) of related flow field at every point based on the Navier-Stokes equation at first. By use of an inertia impaction filter with the inlet width of 20 μm, under the airflow velocity of 7.7 m/s, all the particles with aerodynamic diameter larger than 1.0 μm (Stk ≥ 1.79) can be removed by inertial effect while no particles with diameter smaller than 0.95 μm (Stk ≤ 1.63) impact with the collection plate. For PM particles with different sizes, the trajectories inside an inertial impaction filter can be simulated and traced for 1.0 m/s inlet velocity as shown in Fig. 3 and for other inlet velocities as shown in Supplementary Material 4. We anticipate that there are no fundamental obstacles to extending these new techniques to PM filtrations at higher airflow velocity and this inertial impaction filter will be a start point for future low-cost, high-efficiency, and durable air filter with good thermos-stability, extremely low airflow resistance, and long operation life
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