Environmental applications of electrospun keratin nanofibers

Electrospun nanofibers have gained increasing interest for solving critical environmental issues such as air pollution and water contamination. Electrospinning is based on the application of a high voltage to the viscous polymer solution in order to generate an electrified jet stream from an electrically charged liquid drop that solidifies into nanofibers by solvent evaporation. Electrospinning process parameters lead the production of nanostructured layers with different characteristics (e.g. fiber size, morphology, layer density and thickness). Highly porous and flexible web can act as a membrane separating two distinct phases through processes such as adsorption, distillation, and extraction. High porosity, interconnected open pore structure, high permeability and high surface area per unit volume are very attractive properties in separation technology. One of the advantages of nanofiber membranes is that they can offer, at the same time, filtration and adsorption. Moreover, electrospinning process is scalable; to increase both productivity and covering area, large-scale nanofibre production by multi-jet electrospinning systems can be designed [1]. Many natural materials such as agricultural wastes or industrial by-products have been proposed as low cost adsorbents available in large quantities for heavy metals. Among them, keratin proteins are characterized by a great number of functional groups able to bind cationic species. Keratin is the most abundant non-food protein in nature is available as waste (more than 5*106 t/y) from textile and breeding industry. Considering its applications, it is worth to note that is biocompatible and biodegradable and can be electrospun pure or in blend with other polymers, such as polyamides. Among the natural electrospinnable polymers, keratin is able to remove toxic substances such as formaldehyde, metal ions and dyes efficiently [2]. Moreover, keratin nanofibers integration with nanoparticles as TiO2 and Ag colloidal properly dispersed in the electrospinning solutions improves membrane functionalities such as biocidal action and photocatalytic properties [3].