High Efficiency Particulate Matter Research Articles

Electrospinning of Biodegradable, Monolithic Membrane with Distinct Bimodal Micron-Sized Fibers and Nanofibers for High Efficiency PMs Removal.

Atmospheric particulate matter (PMs) pollution has raised increasing public concerns, especially with the outbreak of COVID-19. The preparation of high-performance membranes for air filtration is of great significance. Herein, the biosynthetic polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was adopted to create a hierarchical structure and biodegradable nonwoven membrane for PMs filtration through a facile directly electrospinning method. The as-prepared membranes with hierarchical structure contain abundant nanowires (5-100 nm) and microfibers (2-5 μm) with different diameter (1000-5000 nm). We have achieved realization of formation mechanisms of such bimodal micro- and nanofibers, which stem from the branching of microfiber at early stage of electrospinning. The PHBV membranes exhibit a very high PM0.3 removal efficiency of 99.999% and PM2.5 removal efficiency of 100% with 0.077% standard atmospheric pressure in the air flow speed of 5.3 cm/s. More importantly, the PHBV membranes can be completely disintegrated within 1 week under composted conditions, indicating the great biodegradability of PHBV membranes. Our work provides insights for the development of biodegradable, high performance air filters for pollutants, molds, bacteria, and viruses.

Electrospinnability analysis of natural cellulose nanofibers for use in high-efficiency particulate matter capture based on rheological behaviors

To aid the development of air filters with high-efficiency fine particulate matter (PM) capture properties, the electrospinnabilities of natural cellulose nanofibers, which considerably affect filter performance, were investigated via rheological behavior analysis. The cellulose nanofibers were prepared by mixing trifluoroacetic acid (to dissolve cellulose) and 1,2-dichloroethane (to improve electrospinnability) with various types of cellulose. The rheological behavior of the precursor solution was analyzed according to mixing time via large amplitude oscillatory shear studies. The electrospinnability of the cellulose precursor solution was investigated based on the flow-induced structural anisotropy characteristics and the storage-loss moduli plot obtained by varying the frequencies. The precursor solution with hardwood pulp (HP) exhibited the highest specific surface area and the lowest combined content of hemicellulose and lignin, and thus, the optimal electrospinnability. The electrospun HP nanofiber sample with an HP content of 1.5 wt% displayed the optimal electrospinnability and the highest specific surface area of 1021 m2/g. It also exhibited high-efficiency PM capture characteristics, such as a PM2.5 capture efficiency and quality factor and an air permeability of 98.99%, 0.27, and 309 cm3/cm2 s, respectively. This study suggests the potential for the development of next-generation green nanofiber air filters using cellulose nanofibers.

Self-Powered Air Filter Based on an Electrospun Respiratory Triboelectric Nanogenerator

High-efficiency particulate matter (PM) filtration has been an important effort in air purification; however, conventional physical filtration mechanisms are inefficient in blocking submicron particles, which are extremely hazardous to public health. Here, a self-powered triboelectric air filter (STAF) with high efficiency in filtering PM of different sizes is demonstrated. The STAF consists of conductive sponges (CSs) and electrospun fibers (nanofibrils, NFs), which constitute a respiratory triboelectric nanogenerator (R-TENG) through the coupling of the electrical difference between both materials and the respiratory airflow. It utilizes a reciprocating airflow drive to generate triboelectric charges and improve electrostatic adsorption, especially for fine particles. In the experiment, the STAF can maintain a filtration efficiency of 98% for PM2.5 and up to 91.5% for PM0.5, which clearly exceeds the level of commercial masks. In addition, the STAF maintains a high filtration capacity after one month of storage and has a good performance life. This research is of great importance to effectively improve air purification capacity, protect personal health, and prevent respiratory diseases, and it is also of great value to the development of self-driven wearable applications.

Electrospun polyetherimide/zeolitic imidazolate framework nanofibrous membranes for enhanced air filtration performance under high temperature and high humidity conditions

Efficient filtration of particulate matter (PM) is the major goal for various air cleaning technologies. However, most existing air filters are conducted at room temperature with a relative humidity (RH) of around 45%, ignoring the fact that many operate under high temperature and RH above 90%. Herein, we report the successful fabrication of a polyetherimide (PEI)/zeolitic imidazolate framework-67 (PEI/ZIF-67) nanofibrous membranes using electrospinning technology, which showed steady and high efficiency PM filtration performance under a high temperature of 200 °C and RH of 90%. Compared with pure PEI nanofibrous membranes, the resultant nanofibrous membranes containing 2 wt% of ZIF-67 showed an increase of 112% and 109% in removal efficiency of PM2.5 and PM10, respectively, which are attributed to synergistic effects of enhanced surface roughness, strengthened electrostatic interaction and small pore size by the introduction of the ZIF-67. More importantly, after operating under a high RH of 90% over 70 h, the removal efficiency of such PEI/ZIF-67 nanofibrous membranes remained almost unchanged. Density functional theory calculations suggested that the ZIF could efficiently reduce water adsorption and thereby avoid the PEI being damaged by water. Such a finding demonstrated that the ZIFs should be promising candidates for designing highly stable nanofibrous membranes under extremely high RH and high temperature conditions.

Porous-foam mullite-bonded SiC-ceramic membranes for high-efficiency high-temperature particulate matter capture

Membranes of ceramic foams exhibit excellent prospects for application in the field of high-temperature particulate matter (PM) capture. Production of ceramic membranes that can achieve good removal efficiency as well as low pressure drop in high-efficiency PM filtration represents a great challenge. This paper reports on the preparation of porous-foam mullite-bonded SiC-ceramic membranes (MSCMs) with a 3D interconnecting pore network by a direct foaming method combined with gel-tape casting. The produced MSCMs contained large pores with a diameter of 60–150 µm, which were interconnected with abundant small functional (for filtering) pores of<10 µm. Increasing the amount of the foaming agent favored the increase of porosity of the MSCMs, which was tailored between 69.2% and 84.1%, while the bending strength decreased from 10.3 to 4.0 MPa, respectively. High PM filtration efficiency (70.2%, 90.1%, and 94.6% for PM0.3, PM2.5, and PM10, respectively) and ultra-low pressure drop (27 Pa) were also recorded. Hence, the produced MSCMs qualify for application as high-temperature PM filters. This work also aims at providing a new insight into developing high-efficiency air filters.

Preparation and Characterization of an Electrospun PLA-Cyclodextrins Composite for Simultaneous High-Efficiency PM and VOC Removal

Electrospinning is known to be a facile and effective technique to fabricate fibers of a controlled diameter-distribution. Among a multitude of polymers available for the purpose, the attention should be addressed to the environmentally compatible ones, with a special focus on sustainability. Polylactic acid (PLA) is a widespread, non-toxic polymer, originating from renewable sources and it can degrade into innocuous products. While the production of fibrous membranes is attractive for airborne particles filtration applications, their impact on the removal of gaseous compounds is generally neglected. In this study, electrospun PLA-based nanofibers were functionalized with cyclodextrins, because of their characteristic hydrophobic central cavity and a hydrophilic outer surface, in order to provide adsorptive properties to the composite. The aim of this work is to investigate a hybrid composite, from renewable sources, for the combined filtration of particulate matter (PM) and adsorption of volatile organic compounds (VOCs). Results show how their inclusion into the polymer strongly affects the fiber morphology, while their attachment onto the fiber surface only positively affects the filtration efficiency.

High-Temperature Particulate Matter Filtration with Resilient Yttria-Stabilized ZrO2 Nanofiber Sponge.

Particulate matter (PM) is a major air pollutant in many regions, jeopardizing ecosystems and public health. Filtration at pollutant source is one of the most important ways to protect the environment, however, considering the high-temperature exhaust gas emissions, effective removal of PM and related pollutants from their sources remains a major challenge. In this study, a resilient, heat-resisting, and high-efficiency PM filter based on yttria-stabilized ZrO2 (YSZ) nanofiber sponge produced with a scalable solution blow spinning process is reported. The porous 3D sponge composed of YSZ nanofibers is lightweight (density of 20 mg cm-3 ) and resilient at both room temperature and high temperatures. At room-temperature conditions, the YSZ nanofiber sponge exhibits 99.4% filtration efficiency for aerosol particles with size in the range of 20-600 nm, associated with a low pressure drop of only 57 Pa under an airflow velocity of 4.8 cm s-1 . At a high temperature of 750 °C, the ceramic sponge maintains a high filtration efficiency of 99.97% for PM0.3-2.5 under a high airflow velocity of 10 cm s-1 . A practical vehicle exhaust filter to capture particles with filtration efficiency of >98.3% is also assembled. Hence, the YSZ nanofiber sponge has enormous potential to be applied in industry.

High-performance inertial impaction filters for particulate matter removal

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.

Necklace-like fiber composite membrane for high-efficiency particulate matter capture

The necklace-like fiber membranes are fabricated using electrospinning technique for high-efficiency PM (particulate matter) capture. Poly-N,N′-[(4,5-dihydroxy-1,2 phenylene)bis(methylene)]bisacrylamide (POHABA) nanospheres as “pearls” are embedded in poly(ethylene oxide) (PEO) and poly(vinylpyrrolidone) (PVP) matrix substrates to make necklace-like fibers. The reason for choosing POHABA nanospheres is due to their broad-spectrum inhibitory effect on bacteria. The diameters of three POHABA nanospheres are controlled to be 190±50, 364±39 and 467±65nm, respectively. The necklace-like structures become more pronounced with the increase of POHABA diameter. The PM2.5 removal efficiencies of PEO necklace-like fiber membranes obtained with electrospinning time of half an hour are in the range from 88.0 to 92.5%. Under the same fabrication conditions, the PEO/POHABA-467 fiber membrane displays better capture efficiency than that of PVP/POHABA-467 fiber membrane. Using thicker PEO/POHABA-467 filter membrane (electrospinning for one hour), excellent removal efficiency of PM2.5 (99.2%) is achieved, which is better than that obtained from other membranes and even commercial QMA filter (Whatman). The necklace-like fiber membranes have a great potential in the fields of aero filter and mask.