Preparation of nanofiber membrane based on recycled keratin from chicken eggshell and its preliminary application in membrane distillation

The inner eggshell membrane (ESM) sanctions the unfettered conveyance of air across the membrane, ensuring the air provision for embryonic development. As such, the electrostatic spinning technique was availed to fabricate large-scale and flat-sheet 'artificial' eggshell membranes by extracting keratin from waste egg membranes. Keratin within eggshell membranes was initially extracted via the chemical reduction method. Subsequently, diverse electrospinning conditions encompassing the type and concentration of additives as well as the electrospinning voltage were utilised to explore their impact on membrane morphology, wetting, and mechanical attributes. Experimental outcomes demonstrated that the ESM-based nanofiber membrane with salubrious morphology, anti-wetting, and mechanical properties could be procured by adding 12 wt% PVA into the keratin solution at 10.5 kV. Eventually, DCMD experiments for the ESM-based nanofiber membrane evinced that a stable water flux (10 LMH) and salt rejection rate could be discerned throughout the 150-min operational tenure, yet its efficacy lags behind other reported membranes. In light of the lofty porosity (>70%) and meager thermal conductivity of ESM (0.04 W/m·K), ESM nanofiber was coalesced with commercial PTFE membrane to fashion a dual-layer porous composite MD membrane utilised in VMD. Experimental findings divulged that the ESM-PTFE hybrid membrane possesses a relatively elevated water flux (30.21 LMH), being commensurate with the reported PTFE-based MD membranes. Accordingly, this research can provide the theoretical underpinning for the fabrication of ESM-based nanofiber membranes by means of the electrostatic spinning approach, and is conducive to the highly efficient and highly valuable exploitation of waste eggshells.