A Chitosan Nanofiber Sponge for Oyster-Inspired Filtration of Microplastics

For the first time, an ultralight chitosan-glutaraldehyde nanofiber sponge (chitosan NF sponge) was prepared. The present work describes its processing from pure electrospun chitosan nanofibers and its use for filtration applications. Chitosan/polyethylene oxide (PEO) nanofibers (NF) were electrospun from acetic acid into 309 +/- 56 nm-thick nanofibers using high-throughput free-surface electrospinning. To yield chitosan NF sponges, PEO was extracted from the defect-free nanofiber mats. From these mats, nanofiber suspensions were prepared followed by casting and freeze-drying. Cross-linking of such obtained pristine chitosan NF sponges with glutaraldehyde improved water stability and resulted in chitosan NF sponges with a bulk density of 5.77 mg cm(-3) and a porosity of 99.59%. The hierarchical pore architecture of the chitosan NF sponges was perfectly suited for particle adsorption as tested for poly(ethylene terephthalate)-microplastic (PET-MP) and Arizona test dust (ISO 12103-1) suspensions. Hydrostatic filtration with chitosan NF sponges reduced turbidity of particle suspensions by 99.46% nephelometric turbidity units (NTU) (PET-MP) and 99.49% (Arizona test dust). An oyster-inspired adsorption setup with 4000 actuated compression/relaxation cycles reduced the turbidity of PET-MP and Arizona test dust suspensions by 80.1 +/- 1.5 and 91.9 +/- 0.3% NTU, respectively. The preparation of biocompatible NF sponges from chitosan marine biomass has been demonstrated. These chitosan NF sponges can be used as efficient filters to tackle environmental challenges such as microplastics.

Automated summary

This study presents the preparation of ultralight chitosan-glutaraldehyde nanofiber sponges for filtration applications. The sponges showed excellent particle adsorption capabilities and significant reduction in turbidity of particle suspensions. This biocompatible filter has potential applications in addressing environmental challenges such as microplastics.