A Sustainable Recycling Alternative: Electrospun PET-Membranes for Air Nanofiltration

Currently, the inappropriate disposal of plastic materials, such as polyethylene terephthalate (PET) wastes, is a major environmental problem since it can cause serious damage to the environment and contribute to the proliferation of pathogenic microorganisms. To reduce this accumulation, PET-type bottles have been recycled, and also explored in other applications such as the development of membranes. Thus, this research aims to develop electrospun microfiber membranes from PET wastes and evaluate their use as an air filter media. The solution concentrations varied from 20 to 12% wt% of PET wastes, which caused a reduction of the average fiber diameter by 60% (from 3.25 µm to 1.27 µm). The electrospun filter membranes showed high mechanical resistance (4 MPa), adequate permeability (4.4 × 10−8 m2), high porosity (96%), and provided a high collection efficiency (about 100%) and low-pressure drop (212 Pa, whose face velocity was 4.8 cm/s) for the removal of viable aerosol nanoparticles. It can include bacteria, fungi, and also viruses, mainly SARS-CoV-2 (about 100 nm). Therefore, the developed electrospun membranes can be applied as indoor air filters, where extremely clean air is needed (e.g., hospitals, clean zones of pharmaceutical and food industry, aircraft, among others).

Nano-HTDMA for investigating hygroscopic properties of sub-10 nm aerosol nanoparticles

<p>Interactions between water and nanoparticles are of great significance for atmospheric multiphase processes, physical chemistry, and materials science. Current knowledge of the hygroscopic and related physicochemical properties of nanoparticles, however, is insufficient due to limitations of the available measurement techniques. Here, we present the design and performance of a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) apparatus. To enable high accuracy and precision in hygroscopicity measurements of sub-10 nm aerosol nanoparticles, systematic and comprehensive calibration criteria of nano-HTDMA have been developed and applied, including sheath/aerosol flow rates, DMA voltage, relative humidity (RH) sensor, temperature sensor, and particle sizing. After calibration, the nano-HTDMA system has been shown to have an accurate sizing and a small sizing offsets between the two DMAs (<1.4%) for aerosol nanoparticles with diameters down to 6 nm. Moreover, to maintain the RH-uniformities that prevent the pre-deliquescence and non-prompt phase transition of nanoparticles within DMA2, the RH of sheath flow is kept as same as that of aerosol flow at inlet of DMA2, and the humidification system and the DMA2 system are placed in a well-insulated and air conditioner housing (±0.1K). Using nano-HTDMA system. We investigate the hygroscopic behavior of aerosol nanoparticles of two inorganic substances (e.g., ammonium sulfate and sodium sulfate). A strong size dependence of the hygroscopic growth factor is observed for ammonium sulfate and sodium sulfate nanoparticles with diameters down to 6 nm, respectively. For size dependence of phase transition, we find a weak size dependence of DRH and ERH of ammonium sulfate nanoparticles with diameters from 6 to 100 nm but a pronounced size dependence of DRH and ERH between 20 and  6 nm for sodium sulfate nanoparticles.</p>

Nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) for investigating hygroscopic properties of sub-10 nm aerosol nanoparticles

Interactions between water and nanoparticles are relevant for atmospheric multiphase processes, physical chemistry, and materials science. Current knowledge of the hygroscopic and related physicochemical properties of nanoparticles, however, is restricted by the limitations of the available measurement techniques. Here, we present the design and performance of a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA) apparatus that enables high accuracy and precision in hygroscopic growth measurements of aerosol nanoparticles with diameters less than 10 nm. Detailed methods of calibration and validation are provided. Besides maintaining accurate and stable sheath and aerosol flow rates (±1 %), high accuracy of the differential mobility analyzer (DMA) voltage (±0.1 %) in the range of ∼0–50 V is crucial for achieving accurate sizing and small sizing offsets between the two DMAs (<1.4 %). To maintain a stable relative humidity (RH), the humidification system and the second DMA are placed in a well-insulated and air conditioner housing (±0.1 K). We also tested and discussed different ways of preventing predeliquescence in the second DMA. Our measurement results for ammonium sulfate nanoparticles are in good agreement with Biskos et al. (2006b), with no significant size effect on the deliquescence and efflorescence relative humidity (DRH and ERH, respectively) at diameters down to 6 nm. For sodium sulfate nanoparticles, however, we find a pronounced size dependence of DRH and ERH between 20 and 6 nm nanoparticles.