Self-cleaning nanofiber membrane for air filtration

By Pablo E. Baltazar On Mar 23, 2022

Indonesian researchers published an article in ACS Omega focusing on the synthesis of PAN-TiO₂-Ag nanofiber membranes via an electrospinning process. The membrane was developed specifically to be able to act as an effective air filtration device.

Study: Synthesis of an electrospun membrane of PAN/TiO2/Ag nanofibers as a potential air filtration media with photocatalytic activity. Image Credit: Kateryna Kon/Shutterstock.com

Harmful effects of air pollution

Air pollution, which can contain hydrocarbons, nitrogen oxides and particulate matter 2.5 (PM2.5), damages the nasal passages and is a risk factor for early mortality. Several studies have shown that a high level of PM_2.5 concentrations can induce a variety of respiratory diseases as well as Alzheimer’s disease and dementia.

Effectiveness of face masks

Wearing masks is a common approach to reducing human exposure to pollutants and preventing disease. With an effectiveness rate of 95%, the N95 face mask is one of the most frequently used variants of face masks in the corporate world.

It is however only suggested for eight hours of use before needing to be replaced with a new mask. Unfortunately, the use of temporary masks increases the amount of face mask waste, which poses a significant risk to the environment. Therefore, self-cleaning masks with superior air filtering capacity are essential.

Figure 1. SEM images of (a) PAN and (b) PAN/TiO₂/Ag nanofiber membranes. (c) EDS spectrum of PAN/TiO₂/Ag nanofiber membrane. © Hartati, Sri, et al. (2022)

Importance of nanofibers

Nanofibers are 1-D structures with dimensions less than one millimeter. Due to their small fiber diameter, large surface area, excellent surface adhesion, light weight and superior permeability, nanofibers have been used in high performance filtration systems. Their pore structures are narrow and convoluted, and they are connected like a barrier, allowing PM_2.5 particles to collect in the air while reducing pressure drop.

Why PAN/TiO₂/Ag Are nanofibers preferred?

PAN/TiO₂Nanofibers/Ag are very efficient considering their operational efficiency and usefulness. These nanofiber membranes have the potential to be used in wastewater treatment and possess high antibacterial action against Escherichia coli and Staphylococcus aureus as well as exceptional electrocatalytic efficiency in dissolving dyes below the visible region. Moreover, pure polyacrylonitrile (PAN) nanofiber membranes and PAN nanofibers containing active material are well known as effective air filtration media with high PM content._2.5 deletion.

Figure 2. Image of a drop of water on the surface of (a) PAN and (b) PAN/TiO₂/Ag nanofiber membranes. © Hartati, Sri, et al. (2022)

Introduction to the electrospinning process

Electrospinning is one of the most common ways to produce nanofibers. A high voltage generator, a syringe pumping mechanism, a nozzle and a collector are the main elements of the spinning process. The syringe pump ejects a free-flowing strand of precursor solution from a nozzle, while the solution is drawn to the manifolds by the intense electrostatic interaction.

The shape of the nanofibers can be tuned by changing process factors such as operating voltage, separation between nozzles and manifolds, flow velocity, and saturation of the polymer solution.

Results and discussion

The FTIR spectrum showed that there is an interaction between Ag and TiO₂suggesting that TiO₂ and Ag react with each other. After one hour of exposure to ultraviolet light, the PAN nanofibrous barrier exhibited good dye degradation on 60 ppm methylene orange drops.

Deterioration with an 80 ppm methylene orange drop, on the other hand, was not achieved. The inclusion of Ag with TiO₂ reduces its optical absorption.

Picture 3. Quality factor of PAN and PAN/TiO₂/Ag compared to results from other studies and commercial membranes. © Hartati, Sri, et al. (2022)

Woven or non-woven nanofiber membrane separation process with permeability is extremely effective in removing PM_2.5 from the air. Pressure drop is an essential characteristic to consider when designing an air filtration system.

Under the same rotation time, the PAN nanofiber membrane exhibited a greater pressure drop than the PAN/TiO₂/Ag nanofiber film. Pressure loss was highest in PAN/TiO₂/ Ag nanofiber membrane (dried for 60 minutes).

PAN/TiO₂The nanofibrous/Ag barrier had an inhomogeneous dimension variation, resulting in huge holes. This large pore size is less effective at filtering out particles.

When the two membranes were centrifuged for 30 minutes, the PAN/TiO₂/Ag nanofiber membrane demonstrated less efficiency in filtering PM_2.5 than the PAN nanofiber membrane. This is due to the structure of the PAN nanofiber barrier. During 60 minutes of spinning, the PAN/TiO₂The /Ag membrane showed an efficiency of 96.9%.

In summary, the spin coating process was used to efficiently construct a PAN/TiO₂/Ag nanofibrous barrier. PAN/TiO₂The nanofibrous/Ag barrier has the ability to be used as a material of filtration systems with self-cleaning capabilities.

Reference

Hartati, Sri, et al. (2022) Synthesis of electrospun PAN/TiO₂/Ag Nanofibers Membrane as potential air filtration media with photocatalytic activity. ACS Omega. Available at: https://pubs.acs.org/doi/10.1021/acsomega.2c00015

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