Stereocomplex Crystallite-Based Eco-Friendly Nanofiber Membranes for Removal of Cr(VI) and Antibacterial Effects

Poly(lactic acid) (PLA) stereocomplex crystallite (SC)-based electrospun nanofibers were fabricated via annealing the as-spun membranes at 100 degrees C for 1 h. The heat-treated nanofibers exhibit enhanced mechanical properties and thermal resistance due to the existence of SCs, which restricts the lactide chain mobility. The formation of SCs increases the intermolecular forces between L-lactide and D-lactide segments, resulting in almost 2 times higher tensile strength (8.52 +/- 0.29 MPa) and 3 times higher Young's modulus (285.48 +/- 1.19 MPa) than that of the untreated membranes, which is benefitting for wider applications. Additionally, a green absorbent named HTA synthesized from tannic acid and hexamethylenediamine was introduced into the nanofibers, giving the membrane richer functions. Based on the abundant reactive functional groups on the surface, small pore size and large surface area-to-volume ratio of the nanofibers, the HTA containing membranes exhibited excellent performance in adsorbing heavy metal ions and inhibiting bacterial growth. This bifunctional membrane showed reusability for 4 cycles with retaining good removal capability of Cr(VI) and antibacterial effects. Furthermore, Cr(VI) was found to be adsorbed and converted to less toxic Cr(III) during the adsorption process, and bacteria, such as Escherichia coli and Staphylococcus aureus, were captured and broken on the surface of the nanofibers. In this study, we focused on a novel eco-friendly bifunctional SC-based PLA nanofiber to repeatedly adsorb metal ions and capture bacteria, and thus it is expected to have potential in various fields in the future.