Document Type : Research Paper
Authors
- Armin Jamali 1
- Hossein Yousefi 2
- Mahdi Mashkour 2
- Steven J. Severtson 3
- Alain Dufresne 4
- Prashant Kumar 5
1 PhD. In Lignocellulosic Composites/Renewable Nanomaterials, Department of Wood Engineering and Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
2 Associate Professor, Department of Wood Engineering and Technology, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran
3 Professor, Department of Bioproducts and Biosystems Engineering, University of Minnesota 2004 Folwell Avenue, St. Paul, Minnesota, 55108, United States
4 Professor, University Grenoble Alpes, CNRS, Grenoble INP, LGP2, F-38000 Grenoble, France
5 Professor, Global Centre for Clean Air Research (GCARE), School of Engineering, Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences (FEPS), University of Surrey Guildford, GU2 7XH Surrey, United Kingdom Institute for Sus
Abstract
Background and Objective: One of the most effective and direct methods to combat various types of air pollution is the use of filters. However, commercially available versions are manufactured from petroleum-based raw materials, and their waste has become a global challenge. In this regard, replacing these materials with bio-based raw materials can potentially not only solve the waste problem but also enhance filtration efficiency. Among these materials are cellulose nanofibers. The focus of most research has been on fabricating air filters via casting method using wood cellulose nanofibers. Studies on bacterial cellulose nanofibers and, fundamentally, investigations into different coating methods of these nanobiomaterials are very limited. Therefore, the present study aimed to investigate and compare the effects of two coating methods—dip coating and fog-spray coating—for fabricating air filter media using wood cellulose nanofibers and bacterial cellulose nanofibers.
Materials and Methods: For this purpose, wood cellulose nanofibers (WCNF) produced by mechanical method with a degree of polymerization of 700-1200 nm and bacterial cellulose nanofibers (BCNF) synthesized by bacteria with a degree of polymerization of 1500-2500 nm were procured from Nanonovin Polymer Company. Cellulosic fabric with a grammage of 30 g/m² was prepared as the substrate for coating from Live Company and cut into dimensions of 15×15 cm. To fabricate the samples, the nanobiomaterials were first diluted to a concentration of 0.5% by weight using distilled water and then coated onto the cellulosic fabric substrate at a grammage of 2 g/m² using dip coating and fog-spray coating methods. The samples were then transferred to a freeze dryer and prepared at -50°C and 0.04 mbar for 24 hours. To evaluate the raw materials used in this study, tests such as Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), and zeta potential measurement were employed. To evaluate and compare the performance of the fabricated samples, tests including field emission scanning electron microscopy (FESEM), particle removal efficiency, pressure drop measurement, and filter quality factor calculation were used.
Results: The results of FTIR and XRD tests showed that the raw materials used, including the fabric substrate, wood cellulose nanofibers, and bacterial cellulose nanofibers, are all cellulose type Iβ, whose chemical similarity potentially enhanced the formation of hydrogen bonds between the nanobiomaterials and the substrate. FESEM images indicated more uniform distribution and a network structure with finer pores in the samples coated via the fog-spray method compared to the dip coating method. Filtration performance evaluation demonstrated that both coating methods achieved over 90% removal efficiency for all particles in the range of 0.3 to 10 microns. The fog-spray method showed superior performance for both types of nanomaterials, which is attributed to the formation of a more uniform surface layer with more precise grammage control. Bacterial cellulose nanofibers, due to their higher degree of polymerization (1500-2500 nm) and more negative zeta potential (-25 compared to -12), showed higher removal efficiency than wood cellulose nanofibers in both coating methods. The best performance belonged to the bacterial cellulose nanofiber sample coated via the fog-spray method, which achieved a removal efficiency of 99.56% for 300 nm particles and a pressure drop of 112 Pa, earning the highest quality factor among all samples. The removal efficiency of 300 nm particles for BCNF-D, BCNF-F, WCNF-D, and WCNF-F samples were 93.92%, 99.56%, 91.63%, and 95.4%, respectively, and their pressure drops were 88±8, 112±7, 96±4, and 118±8 Pa, respectively.
Conclusion: Both dip coating and fog-spray coating methods demonstrated high potential for fabricating bio-based air filter media. However, the media fabricated via the fog-spray method were more efficient than those fabricated via the dip coating method for both nanobiomaterials. On the other hand, the removal efficiency of samples fabricated using bacterial cellulose nanofibers was also higher than those fabricated using wood cellulose nanofibers. The fog-spray method for wood cellulose nanofibers enabled the fabrication of filters with N95 performance and for bacterial cellulose nanofibers enabled the fabrication of filters with N99 performance in this study.
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