Wooden-framed all-cellulose HEPA nanofilter for sustainable air purification.

Conventional high-efficiency particulate air (HEPA) filters are made from non-biodegradable materials, resulting in persistent waste. Herein, we present the development of an all-cellulose HEPA nanofilter (AC-HEPA) membrane composed of fog-sprayed and freeze-dried bacterial cellulose nanofibers (BCNFs) as the active filtration layer, with tissue paper composed of wood-derived cellulose microfibers (CMFs) as the supporting substrate housed within a modular wooden frame sealed with a starch-based adhesive gasket. The particulate matter removal efficiency increased with increasing BCNFs grammage up to 2 g/m2, followed by a decline at higher values. Cyclic relative humidity modulated particulate matter ≤0.3 μm (PM0.3) adsorption in AC-HEPA, with efficiency peaking at high RH. The optimal wooden-framed AC-HEPA achieved a PM0.3 removal efficiency of 99.998% with a pressure drop of only 150 Pa, which falls within the efficiency range specified for H13 and H14 classifications according to the European EN 1822 standard. This demonstrates its strong potential for a scalable and sustainable air filtration system.