Sustainable engineering of coconut coir-derived cellulose acetate: Macromolecular control for charge-neutral, most-penetrating-particle-size-resolved air filtration.

Here, we report the fabrication of ultrafine, high efficiency cellulose acetate (CA) electrospun fibrous membranes from coconut husk derived cellulose. Cellulose isolated from coconut husk was acetylated to afford CA that remained spinnable in acetone/DMAc mixtures. The effects of polymer concentration, solvent ratio, and metal additives (AgNPs and CuSO4) on solution properties, membrane structure, and filtration performance were systematically examined. Viscosity measurements showed consistent shear-thinning behavior for all formulations. In contrast, solution conductivity increased substantially after metal incorporation, particularly for CA-CuSO4. SEM revealed pronounced fiber refinement in the metal-containing systems, while BET/BJH analysis showed strong formulation dependence of N2-accessible surface area and mesopore volume, with CA-AgNPs exhibiting the highest surface area. FTIR deconvolution indicated local perturbation of oxygen-centered environments after metal incorporation, and XRD confirmed that all membranes remained predominantly amorphous. Under charge-neutralized, size-resolved NaCl aerosol testing, all membranes displayed a clear most penetrating particle size (MPPS) in the 89-121 nm range. CA 15% (2:1) and CA-AgNPs gave the highest minimum quality factors, 2.31 × 10-2 and 2.28 × 10-2 Pa-1, respectively, demonstrating an effective route to MPPS-optimized CA air filters. These results highlight the potential of biomass-derived CA for sustainable air filtration applications.