Airborne Nanoparticles Filtration by Means of Cellulose Nanofibril Based Materials

Nanoparticles in air are of particular concern for public health and employee exposure in work-places. Therefore, it is very important to prepare effective filters for their removal. In this work filters were prepared from nanocellulose, i.e. cellulose nanofibrils (CNF). CNF was produced using two methods giving two different qualities of CNF. One quality had negative charges on the fibril surfaces while the other was neutral, and had in addition thinner fibrils compared to the other qualities. Filter samples were produced from water dispersions of CNF, by removal of the water by freeze drying. The performance of the CNF based filters was assessed and compared with filters based on synthetic polymer fibres. The ability to collect NaCl particles with a broad size distribution, ranging from nanometer to micrometer scale, was determined. CNF filters showed quality values comparable with the synthetic polymer based filters. Filters based on both the two CNF qualities had very good filtration efficiency for a given pressure drop across the filter.