Green Synthesis of Nano-Iron Oxide Particles using Drynaria quercifolia Root Extract for Efficient Dye Adsorption in Wastewater Treatment

Rising water pollution from industrial dyes demands sustainable and eco-friendly treatment methods. The green synthesis of nanomaterials presents a viable alternative to conventional techniques, reducing environmental risks while enhancing efficiency. This study reports the green synthesis of Drynaria quercifolia extract-mediated nano-iron oxide particles (DQNIO). The resulting DQNIO displays a UV absorption peak at 236 nm, XRD reflection of spinel Fe₃O₄ (a notable peak at 311), and a characteristic IR peak (Fe–O) at 536.77 cm⁻¹. The DQNIO particles (~ 20 nm) exhibit high surface area (360 m²/g), mesoporosity (10–50 Å), colloidal stability (zeta potential: –26.4 mV) and superparamagnetism (Ms = 17.08 emu/g). DQNIO achieves maximum adsorption capacities of 77.7 mg/g for Congo Red (pH 4) and 59.9 mg/g for Rhodamine B (pH 8). It follows pseudo-second-order kinetics and correspondingly provides a better fit to the Freundlich and Langmuir isotherms. FTIR and zeta-potential analyses confirm dye binding via sulphonate-Fe ligand exchange, hydrogen bonding, coordinate bonding, and π–π stacking. Additionally, DQNIO demonstrates potent antibacterial activity, yielding 33.0 mm inhibition against E. coli and 31.0 mm against S. aureus, surpassing the inhibition of other green-synthesized iron oxides. An eco-scale assessment (81%) and low estimated cost (≈INR 780/kg) validate the sustainability and economic viability of this approach. The findings highlight the dual functionality of nano-iron oxide particles as effective adsorbents and antimicrobial agents.