Sprayable colloidal cellulose nanocrystal dispersions for efficient PM2.5 capture and removal

An active, filter-free strategy for removing fine particulate matter characterized by aerodynamic diameters of <2.5 μm, or PM 2.5 , using aerosolized dispersions of sulfated cellulose nanocrystals (CNCs) is demonstrated. Laboratory-prepared bacterial cellulose nanocrystals (BCNCs) and industrially manufactured CelluForce CNCs were validated. Transmission electron microscopy, dynamic light scattering, zeta potential analysis, and conductometric titration were employed to characterize the morphology, average hydrodynamic diameters, zeta potentials, and sulfate half-ester contents of CelluForce CNCs and BCNCs, respectively. Using a purpose-built chamber–nebulization platform for controlled exposure to incense-derived PM 2.5 , both types of aerosolized CNC dispersions at 1% (w/v) delivered substantially higher PM 2.5 removal than aerosolized ultrapure water microdroplets. Additionally, no statistically significant difference in PM 2.5 removal efficiency between the two CNC sources was observed, as analyzed by one-way analysis of variance (ANOVA), supporting source-independent performance. The CelluForce CNC dispersion at 2% (w/v) exhibited the highest average PM 2.5 removal efficiency of 93.1 ± 2.7%. A plausible PM 2.5 capture mechanism by aerosolized sulfated CNC dispersions was proposed based on time-resolved PM 2.5 capture monitored by scanning electron microscopy and elemental analysis by energy-dispersive X-ray spectroscopy. In contrast to conventional passive air filtration, the aerosolized CNCs remained mobile and became incorporated into PM-CNC composite aggregates upon exposure to particulate matter. This study demonstrates sprayable, renewable, and potentially biodegradable CNC dispersions as a high-efficiency PM 2.5 scavenging medium for localized, scalable, and filter-free mitigation (e.g., indoor hotspots and community-level episodes), aligning with the need for non-toxic and environmentally benign dust removers suitable for residential settings.