Green and Size-Specific Synthesis of Stable Fe–Cu Oxides as Earth-Abundant Adsorbents for Malachite Green Removal

Many challenges remain for the mass production of nanoparticles for the removal of contaminants from water, primarily due to the complexity of the synthetic protocols involved and the use of hazardous reagents. Although the development of phytosynthetic methods for the green fabrication of nanomaterials have seen keen interest, there remains much scope for improvement in terms of maximizing adsorption capacity and controlling the size of the nanoparticles produced. A green and sustainable pathway is described using Virginia creeper (Parthenocissus quinquefolia) leaf extract in the presence of oxalic acid for the synthesis of earth abundant Fe,Cu-based nanoparticle adsorbents. This optimized green method could produce Fe,Cu-based nanoparticles with a remarkably high maximum adsorptive capacity (1399 mg g–1) for aqueous Malachite Green (MG) removal. Furthermore, various particle sizes (between 160 and 1000 nm) were attained by simply varying the amount of oxalic acid. The synthesized adsorbent displayed other excellent characteristics, including (i) maintaining a high adsorption capacity over a wide range of pH conditions, (ii) remaining chemically stable under an ambient storage environment, and (iii) having good recycling potential, with consistent removal efficiency observed over four adsorption/desorption cycles. This work not only promotes the use of natural, earth-abundant, and renewable resources in synthesizing novel and efficient absorbents but also provides a simple, convenient, and cost-effective strategy for the purification of dye-laden wastewater.