ACS Sustainable Chemistry & Engineering
pubs.acs.org/journal/ascecg
Research Article
Figure 4. Molding approaches for EFB/(hairy) cellulose fiber nonwovens through (A) never-dried state and (B) steam-rewetted state. (C) Deformation stage by introducing a load over a metallic base. (D) The deformed EFB/(hairy) cellulose fiber nonwovens. Moldability results for EFB/(hairy) cellulose fiber nonwovens using (E) never-dried approach and (F) steam-rewetted approach. R denotes radius. The illustrations were designed using BioRender.com.
used as the challenge particles and the size distribution of NaCl particles used can be seen in Supporting Information. We quantified the concentration of NaCl PM of less than 1 μ m (PM 1 ), 2.5 μ m (PM 2.5 ), and 4 μ m (PM 4 ) both upstream and downstream of the EFB/(hairy) cellulose fiber nonwovens. From Figure 2A, it can be inferred that the randomly arranged EFB fibers in the nonwoven without any cellulose fibers as binder could create a more tortuous path for the challenge NaCl particles and offer some level of particulate capture efficiency, 15 albeit at a lower PM 1 , PM 2.5 , and PM 4 filtration efficiency of ∼ 25%, ∼ 33%, and ∼ 42%, respectively. Increasing the loading and refining time of the (hairy) cellulose fiber binder improves the particulate filtration efficiency of the resulting EFB/(hairy) cellulose fiber nonwovens. At 10 wt % unrefined cellulose fibers as the binder, the particulate filtration efficiency was measured to be ∼ 54%, ∼ 71%, and ∼ 82% for PM 1 , PM 2.5 , and PM 4 , respectively. To achieve a particulate filtration efficiency of >90% for PM 1 , PM 2.5 , and PM 4 , one could keep the hairy cellulose fiber loading constant at 10 wt % and use hairy cellulose fibers with higher degree of fibrillation (i.e., cellulose fibers refined for 20 and 30 min) or to increase the loading of the (hairy) cellulose fibers >10 wt %. For the
latter, using hairy cellulose fibers could achieve a PM 1 filtration efficiency of 99%. Such particulate filtration efficiency is comparable to the air filter bags made from polyester 48 and even HVAC air filters made from polypropylene. 49 The high particulate filtration efficiency of the EFB/(hairy) cellulose fiber nonwoven stems from the “void filling” effect by the (hairy) cellulose fibers within the EFB nonwoven structure. 50 This then leads to two key particulate filtration mechanisms: (i) size exclusion, where the NaCl particles larger than the now smaller pores in the nonwoven structure are physically trapped, and (ii) interception, where smaller particles adhere to fibers as they pass through the now more tortuous paths created by the more fibrillated hairy cellulose fibers. 51 An aerosolized particulate filter may achieve high filtration efficiency simply by the virtue of increasing the thickness of the filter but this can also lead a high pressure drop, 52 which is undesirable for practical applications. To assess the balance between aerosolized particulate filtration efficiency and pressure drop, the quality factor (QF) is often used 53
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https://doi.org/10.1021/acssuschemeng.5c00041 ACS Sustainable Chem. Eng. 2025, 13, 6209 − 6221
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