Composite electrospun nanofibres for treatments of air and water

The objective of the work is to develop composite nanofibres suitable for filtration of air and water by merging biopolymer processing and sol-gel techniques using electrospinning technology. In particular the attention will be focused on the production of innovative multifunctional filter media by integrating keratin nanofibre membranes with inorganic nanoparticles (as nanometals or nanometal oxides). Among the functional polymers, bio-based polymers as proteins (keratin or fibroin) or carbohydrates (chitosan), offer an attractive solution for the preparation of nanofibrous membranes able to adsorb heavy-metal ions, dyes and VOCs. The advantage of keratin-based nanofibre membranes is that they can offer both removal of suspended small particles filtration (due to the controlled porosity and small pore size) and adsorption of heavy-metals, dyes and VOCs, such as formaldehyde (due to the presence of many functional groups able to bind toxic substances). Nanometals and/or nanometal oxides improve membrane functionalities towards removal of bacteria (antimicrobial, low bio-fouling) and exploitation of photocatalytic reactivity (removal of drugs, antibiotics, pesticides, and fertilizers), respectively. The keratin nanofibrous membranes were tested as adsorbent of heavy metal ions. The pure keratin nanofibres showed excellent adsorption performances for copper ions reaching removal efficiency of 90% and their selectivity for different metal ions follows the order Cu(II)>Ni(II)>Co(II). Keratin nanofibre membranes were also tested as adsorbent of dyes. Methylene Blue was used as an organic dye. Keratin nanofibres showed a maximum adsorption capacity of 170 mg/g, reached at the initial MB concentration of 250 mg L-1, pH 6, adsorbent dosage of 1g L-1 and contact time of 24 hours. Keratin nanofibres showed an adsorption capacity towards Methylene Blue of two order of magnitude higher than that of wool fibres, due to their high specific surface. Finally, the ability to remove airborne formaldehyde of keratin nanofibres deposited on the polypropylene conventional air filters was studied in order to test these membranes for active air cleaning. The keratin nanofibres are able to reduce the airborne formaldehyde concentration up to 100%. In this work, different strategies will be followed to prepare nanoreactive membranes active for selective removal of different classes of pollutants in water and air treatment. In particular, electrospinnable keratin solutions doped with inorganic nanoparticles were prepared by mixing keratin solutions with Ag and TiO2 nanopowder or Ag and TiO2 nanosol. The inclusion of inorganic nanoparticles, with antibacterial or with photo-catalytic/self-cleaning properties, in electrospun nanofibrous materials can transfer such new functions to final polymeric product towards the creation of hybrid multifunctional materials.