An eco-friendly adsorption process for the removal lead ions [Pb (II)] from aqueous solutions using wetland macrophytes <i>Nymphaea pubescens</i> as natural adsorbent

Heavy metal pollution is acknowledged as a major issue at hazardous waste sites. Lead, like other heavy metals, is particularly dangerous at low quantities. The aim of the present study was to explore the potential of Nymphaea pubescens leaves (NPL) as a biosorbent for the removal of lead ions (Pb (II)) from aqueous solutions. Energy-dispersive X-ray (EDX), zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) were used to evaluate the adsorbent. The batch experiment was conducted to investigate the impact of several variables, including initial metal ion concentration, pH, adsorbent dose, contact time, and temperature. The nonlinear isotherm models of Toth, Langmuir, Temkin, Freundlich, and Dubinin-Radushkevich were implemented to analyze the equilibrium adsorption data. The batch results indicated that NPL can remove 99.58% Pb (II) from an aqueous solution. With the highest correlation coefficient, (R2 = 0.994), lowest error function (χ2 = 2.18), and the highest adsorption capacity (qm = 50.09 mg g-¹), Langmuir was determined to be the most suitable model for the experimental data. According to kinetic studies, the Elovich model effectively described the adsorption kinetics (R2= 0.995 and χ2= 0.111). With a positive value for ΔH0 (5.72 kJ mol-¹) and a negative value for ΔG0 (-11.44 to -12.57 kJ mol-¹), the adsorption is an endothermic and a spontaneous process. This study offers a sustainable approach with practical potential, providing useful insights to enhance strategies to counteract lead pollution in water resources.