INTRODUCTION
Air pollution is an environmental problem that poses a significant threat to human health worldwide, ranging from minor upper irritation to chronic respiratory and heart disease, premature mortality, and lung cancer 1,2. The World Health Organization (WHO) data reveals that 99% of the world’s population is exposed to air containing elevated levels of pollutants 64. One of the primary components of the most harmful air pollution, impacting air quality, human health, and ecosystems, is particulate matter (PM) 3,4. PM is a general term for solid and liquid particles of small size suspended in air 5,6. Most of the PM comes from motor vehicle emissions 7, coal combustion 8, industrial emissions 9, and the burning process 10.
Many epidemiological data and clinical studies prove that PM
exposure harms human health. Among the various impacts, one of the
notable consequences is the onset of cardiovascular dysfunction
11. The long-term inhalation of PM,
especially PM2.5 (diameter size < 2.5
\mu
Nanofiber-based filtration membranes, known for their high PM
removal efficiency, offer a promising solution for some applications,
such as enhancing face masks and respirators for effective virus
protection and reducing air pollution from PM
16. Nanofiber, with an average
diameter below 1 \mu
Nanofiber membranes can be fabricated through several methods, including electrospinning. Electrospinning is a method capable of producing selective, cost-effective, and flexible membranes for various polymers 22,23,24,25,26. Electrospinning can fabricate fibers continuously with diameters ranging from micro to nanometers 19,27,28,29,30,31,32,33,34. Many polymers can be used for nanofiber membrane fabrication, including polyacrylonitrile (PAN) 35,36, polyvinyl pyrrolidone (PVP) 37,38, polyvinyl acetate (PVAc) 39,40,41, polyvinyl alcohol (PVA) 42, polystyrene (PS) 43,44, polypropylene (PP) 45,46, and others. Among these polymers, nanofiber membranes made from PAN polymers are often applied as filtration media because they have good chemical, mechanical strength, and thermal stability 47. In addition, it also has an average diameter of about 141 nm48. Considering the average fiber diameter achieved by previous researchers, the PAN membrane is predicted to filter PM that might pass through the membrane. However, research has been widely reported on fabricating nanofiber membranes using PAN polymer material by electrospinning as an air filtration membrane 49,50. In this study, we focus on the effect of PAN nanofiber thickness on its performance as a PM filtration membrane. Cigarette smoke, which is widely dispersed in the air, was used as a PM source to mimic the ability of the fabricated membrane to the real sample. The morphology and functional groups of the PAN nanofiber membrane were observed by scanning electron microscope (SEM) and Fourier-transform infrared (FTIR). The fabricated PAN nanofiber-based PM filtration membrane from this research is expected to be utilized as an air filter in indoor devices and respiratory protective equipment, such as masks and respirators.
MATERIAL AND METHODS
Reagents And Instruments
Polyacrylonitrile (PAN) powder (Mw 150,000 g.mol-1) dan N, N-dimethyl formamide (DMF) (Mw 73.09 g.mol-1) were all produced by Sigma Aldrich, Singapore. A commercial cigarette was used as a PM source (PT. Gudang Garam Tbk.). Scanning electron microscopy (SEM, JEOL JSM-6510) and Fourier-transform infrared spectroscopy (FTIR, Thermo Nicolet iS10) were employed to investigate the morphologies and chemical compositions of the fabricated PAN nanofiber-based PM filtration membrane. The particle counter (CEM DT-9881) and digital manometer (HT 1890) were utilized to measure the PM concentrations and pressure drop of the membrane before and after passing the membrane. ImageJ and OriginLab software were used to measure the diameter of the nanofiber and visualize the data in the graph, respectively.
Nanofiber Fabrication Process
PAN solution, with a concentration of 6 wt%, was achieved by
dissolving the PAN polymer in DMF. The solution was stirred for 2
hours at 40 ^\circ
Filtrations Test Process
In this research, cigarette smoke was used as the PM source, and
the PM filtration setup is shown in figure 1. The test was
carried out by placing the PAN nanofiber-based membrane in the
membrane holder. PM concentration was measured using a particle
counter in each tank (before and after passing the membrane,
recorded as \mathrm{C_0}
where \eta
RESULTS AND DISCUSSION
Morphology, Size Analysis, And Chemical Composition of PAN Nanofiber-Based Membranes
Figure 2 shows the SEM images of PAN nanofiber with two
different magnifications of 5,000× and 3,000×. PAN nanofiber is seen
to have a smooth and continuous morphology; these results are in
accordance with previous studies
58,59.
Based on the SEM image, nanofiber diameters were measured using
ImageJ software (see figure 3a). The measurement results
show that the nanofibers have a diameter of 224 nm to 738 nm, with
an average diameter of (410 ± 78) nm, tending to have a small
diameter. The small diameter is very beneficial in increasing the
efficiency of the nanofiber-based PM membrane on the Kuwabara model,
which shows that the filtration efficiency is inversely proportional
to the diameter of the nanofiber
47,60,61,62.
In this study, the thickness of the nanofiber membrane was varied
using the volume of solution, namely 4 mL, 6 mL, and 8 mL (denoted
as NF-4, NF-6, and NF-8 membranes, respectively). Figure 3b
shows the measurement of nanofiber membrane thickness. The thickness
of the membrane is measured by measuring the results of the SEM
cross-sectional image of the membrane using ImageJ software.
Measurements were made three times (n = 3) at different locations.
The result shows that nanofiber membranes have a thickness of (52 ±
2) 63.
In this study, the thickness of the nanofiber membrane was varied
using the volume of solution, namely 4 mL, 6 mL, and 8 mL (denoted
as NF-4, NF-6, and NF-8 membranes, respectively). Figure [FIGREF:3]b
shows the measurement of nanofiber membrane thickness. The thickness
of the membrane is measured by measuring the results of the SEM
cross-sectional image of the membrane using ImageJ software.
Measurements were made three times (n = 3) at different locations.
The result shows that nanofiber membranes have a thickness of (52 ±
2) \mu
In addition to confirming the morphology and thickness of the PAN
nanofibers by SEM images, we also provided FTIR spectra of
fabricated nanofibers (see figure 3c). An FTIR spectra was
conducted to identify functional groups and chemical composition of
the fabricated nanofiber. The PAN nanofiber has a peak at a
wavenumber of 2923.84 cm-1 and 2243.07 cm-1,
indicating the presence of C-H and C\equiv
PM Filtration Performance
PM filtration performance tests were carried out to determine the
ability of fabricated PAN nanofiber to filter the PM with a size
below 2.5 \mu
CONCLUSION
This study successfully produced polyacrylonitrile (PAN) nanofiber
membranes of various thicknesses for particulate matter (PM)
filtration from cigarette smoke, employing the electrospinning
technique. Scanning electron microscopy (SEM) images and
Fourier-transform infrared (FTIR) spectra were provided to examine the
nanofiber membrane’s morphology and chemical composition. Nanofiber
thickness was achieved of (52 ± 2) \mu