Development, characterization, and photocatalytic evaluation of poly(ε-caprolactone) based nanofilms reinforced with green cobalt oxide nanoparticles for methylene blue dye degradation

This study aims to develop and characterize a poly(ε-caprolactone) (PCL) nanofilm functionalized with green-synthesized tricobalt tetraoxide nanoparticles (Co 3 O 4 -NPs) using Ginkgo biloba extract to photodegrade methylene blue (MB) under visible irradiation. The films were produced by electrospinning and subsequently immersed in suspensions containing 5 and 10 wt.% Co 3 O 4 -NPs, characterized by XRD, FEG-SEM/EDS, ATR-FTIR, contact angle measurements, mechanical testing, and applied in phytotoxicity assays, photochemical degradation, and photodegradation of MB. The XRD diffractograms confirmed the preservation of the characteristic crystalline peaks of PCL, while the micrographs revealed the formation of Co 3 O 4 -NPs agglomerates dispersed over the polymeric fibers. Moreover, the incorporation of Co 3 O 4 -NPs in the nanocomposite reduced the mechanical strength, while maintaining the polymer's hydrophobic character. Phytotoxicity tests showed no toxicity to Brassica oleracea seeds, and photochemical degradation indicated that the nanocomposite containing 5 wt.% of Co 3 O 4 -NPs was the most stable. PCL@5%Co 3 O 4 -NPs exhibited the photocatalytic activity under visible radiation, achieving 63.41% MB degradation at the end of 180 min. Furthermore, the reuse assay demonstrated catalytic stability over three cycles, with the PCL@5%Co 3 O 4 -NPs maintaining efficiency above 50% despite a slight decrease attributed to leaching or obstruction of active sites. Tests with scavengers indicated that the process is mediated by hydroxyl radicals (•OH - ), valence holes (h + ), and free electrons (e - ), making PCL@5% the most promising for applications under visible light. Therefore, PCL@Co 3 O 4 -NPs nanofilms represent a sustainable and efficient material for treating dye-containing wastewater, correlating nanobiotechnology and sustainable development, and offering a promising, eco-friendly solution to a critical environmental issue.