Thermally treated lanthanum oxide nanoparticles-embedded polyamide composite nanofiber membrane for enhanced mechanical properties and phosphorus adsorption kinetics

Lanthanum oxide (La₂O₃) nanoparticles-embedded polyamide 6 nanofiber membranes were electrospun using hexafluoroisopropanol (HFIP) as the solvent. Unlike other solvents such as formic acid and an acetone: trifluoroacetic acid (ace: TFA) mixture, HFIP allowed La₂O₃ nanoparticles to remain well-suspended without altering their composition. Various material characterizations confirmed La₂O₃ nanoparticles are well embedded in polyamide nanofibers. The phosphorus uptake capacity remains consistent when La₂O₃ nanoparticles were embedded in polyamide 6 nanofibers (∼10.4 mg/g) compared to free suspended nanoparticles (∼10.3 mg/g). By optimizing post-thermal treatment, both mechanical strength (e.g., yield strength (σ_y) from 1.68 × 10⁷ to 2.67 × 10⁷ Pa) and adsorption kinetics (e.g., k₂ from 2.63 × 10^-2 to 1.49 × 10^-1 g/(mg·min)) were improved. This study confirms that post thermal processing can be used to further enhance the mechanical properties of the composite nanofiber membrane while maintaining its phosphate adsorption capabilities and improved adsorption kinetics.