Synthesis of a Novel Supermagnetic Fe3O4 Nanoparticles and their Congo Red Dye Removal, Cytotoxic, Antioxidant, and Antimicrobial Activities

Abstract Plantago lanceolata is a traditional medicinal plant that has attracted significant interest from researchers due to the use of its physiologically active components, particularly polyphenolics (flavonoids, hydroxycinnamic acids), in various fields. The aim of this study is to synthesize iron oxide (PLE@FeNPs) nanoparticles using a green synthesis approach with Plantago lanceolata ( P. lanceolata ) leaf extracts, characterize them, evaluate their in vitro effects, and assess their use in the removal of Congo red (CR) from wastewater. We carried out the physicochemical characterization of the nanoparticles using UV–Vis, FT-IR, and XRD spectroscopies; TEM and SEM microscopy; and Zetasizer particle size analysis. While the distinct peaks in XRD confirm the crystalline structure, TEM has determined an average particle size (8 nm) for PLE@NPs with deformed spherical nanoparticles. The FT-IR spectra showed that bioactive compounds from P. lanceolata were involved in the participation of PLE@FeNPs. EDX confirmed the presence of iron in the designed PLE@FeNPs. The antibacterial, antioxidant, and anticancer analyses of the studied PLE@FeNPs revealed significant activities. We investigated the adsorption kinetics of CR on PLE@FeNPs, taking into account initial dye concentration, different pH levels, adsorbent dosages, and temperature. At optimal conditions (concentration, 50 ppm; dosage, 15 mg; pH, 8), the degradation of CR dye in sunlight was found to be 99%. The small size of PLE@NPs (8 nm) and the more negative zeta potential (− 12.2 mV) support this situation. The equilibrium data demonstrated a good fit to the Langmuir isotherm model, outperforming the Freundlich isotherm model. The results showed that the pseudo-second-order kinetic model accurately described the kinetic data. PLE@NPs exhibited significant antioxidant, antimicrobial, and anticancer activities. This situation suggests that the nanocomposition of PLE@NPs obtained through the green route may have improved efficiency due to various synergistic effects. Overall, these results pave the way for further applications in dye removal and biological applications of environmentally friendly PLE@FeNPs. Graphical Abstract