Removal of lead (II) from aqueous solutions using iron nanoparticles synthesized from watermelon peel extract

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Abstract

In this research, we explored the synthesis and application of iron oxide magnetic nanoparticles functionalized with watermelon peel extract (NP-FeO-CL) using an eco-friendly approach. These nanoparticles were characterized by FT-IR, SEM, and UV-Visible spectroscopy, confirming their structure, magnetic properties, and purity. Their efficiency was evaluated in removing lead (Pb) ions from aqueous solutions under various experimental conditions, including variations in contact time, adsorbent mass, pH, temperature, and initial Pb concentration. The results showed a maximum Pb removal of 91.40% under optimum conditions (pH=4, temperature=25 °C, and contact time=5 min). Adsorption isotherms indicated an excellent fit to the Freundlich model (R²=0.94, KF=16.99 mg/g, n=1.97), reflecting heterogeneous and multi-layered adsorption. Likewise, a good fit to the Langmuir model (R²=0.91) was observed, suggesting a single-layer adsorption with a maximum adsorption capacity q_max of 47.16 mg/g. As for the kinetics, the pseudo-second order model adequately described the process (R²=0.99), suggesting that the adsorption rate is controlled by the availability of active sites. Thermodynamic analysis evidenced that the process is spontaneous and favorable at moderate temperatures, although the efficiency decreases at higher temperatures. This study highlights the potential of NP-FeO-CL as a sustainable and efficient solution for the remediation of water contaminated with heavy metals. Moreover, the green synthesis method used not only minimizes the environmental impact but also promotes the reuse of agro-industrial waste, contributing to the circular economy. Tests conducted under real conditions, such as in mining waters fortified with Pb, validated its practical applicability, achieving efficiencies above 90% in the first minutes of the process. These results position NP-FeO-CL as a versatile tool for treating contaminated water, with a significant impact on the sustainable management of water resources and environmental protection.

Keywords

Pb adsorption / mining wastewater treatment / green synthesis / adsorption isotherms / nanoparticles

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