Cellulose nanofiber aerogels modified with titanium dioxide nanoparticles as high-performance nanofiltration...

Air pollution is a major environmental and public health issue. Each year, large amounts of particulate matter (PM) and other harmful pollutants are released into the atmosphere. Conventional polymer nanofiber filters lack the functionality to capture ultrafine PM. As a sustainable alternative, this work developed titanium dioxide (TiO₂) nanoparticle surface-modified cellulose nanofiber (CNF) aerogels for PM_2.5 filtration. CNFs were extracted via mechanical disintegration to diameters below 100 nm. The nanofibers were functionalized with 1.0-2.5 wt% TiO₂ nanoparticles using citric acid cross-linking. Cylindrical aerogels were fabricated by freezing and lyophilizing aqueous suspensions. Structural, morphological, thermal, and mechanical properties were characterized. TiO₂ modification increased density (11.8-19.7 mg/cm³), specific surface area (287-370 m²/g), and Young's modulus (33.5-125.5 kPa) but decreased porosity (99.6 %-97.7 %), pore size (20.2-15.6 nm) and thermal stability compared to unmodified cellulose aerogels. At 2.5 wt% loading, the optimized aerogels achieved 100 % absorption of 0.1-5 μm particulates owing to reduced pore size. Despite enhanced filtration capabilities, the modified CNF aerogels retained inherent biodegradability, degrading over 70 % within one month of soil burial. This pioneering research establishes TiO₂ functionalized CNF aerogels as promising sustainable alternatives to traditional petroleum-based air filters, representing an innovative approach to creating next-generation nanofiltration materials capable of effectively capturing fine and ultrafine particulate matter pollutants.