Nanofibre filters for air and water purification by multi-jet electrospinning

Air pollution and water contamination are serious environmental issues. Small aerosol particles and volatile organic compounds (VOCs) in air adversely affect human health. The discharge of wastewater containing dyes and heavy metals harms the aquatic life and limits water resources. New filtration systems based on electrospun nanofibres have been proposed. Nanofibre filters showed an enhance filtration efficiency to remove ultrafine particulate from air stream due to small pore size. Nanofibres composed by polymers with functional groups (i.e. keratin) allow the depuration of water from pollutant compounds such as metal ions and dyes, or air purification from VOCs (e.g. formaldehyde) with improved performances thanks to the high specific surface. Academic and industrial interest for electrospinning raised in the 1990s, but up-scaling of the process have to reach in order to fulfil industrial production requirements. Large-scale electrospinning systems should be designed to increase productivity, allowing continuous nanofibre production and deposition. One approach is the use of multi-nozzle electrospinning plant. In this work, an electrospinning pilot plant equipped with 62 nozzles was designed and developed. Electrospun nanofibres were continuously deposited on textile substrates, moved during electrospinning by a roll-to-roll system for filter production. The shifting speed of the substrate influenced thickness, porosity and density of the deposited nanofibre layers. Performances of keratin-based filters in terms of filtration efficiency and air permeability were evaluated, as well as the adsorption of formaldehyde. Moreover, removal of metals ions (copper, nichel, cobalt) and methylene blue were measured by dynamic adsorption tests.