Green synthesis of iron nanoparticles from Pouteria caimito: An effective adsorbent for mercury (Hg) in aqueous solutions

Mercury is one of the most toxic heavy metals to human health, highlighting the urgent need to develop highly efficient adsorbents for its removal. This study investigates the eco-friendly synthesis of magnetite nanoparticles using Pouteria caimito extract (MNps-PC) as an innovative adsorbent for the removal of mercury (Hg) from aqueous solutions. The synthesis was carried out via a co-precipitation method, and characterization was performed using techniques such as UV–visible spectroscopy, FTIR, TEM, SEM, EDS, and laser granulometry. The adsorption effect was evaluated using Langmuir and Freundlich isotherm models, complemented by pseudo-first and pseudo-second order kinetic models to analyze the process behavior. Adsorption tests revealed that the process fits pseudo-second order kinetics and the Langmuir isotherm, achieving a notable adsorption capacity of 52.63 mg/g and a removal efficiency of 96 %. Desorption, conducted with HCl and HNO3, was limited (1.91 % and 2.05 %, respectively), indicating a high stability of the adsorption. Consequently, this work presents a sustainable method for obtaining an environmentally friendly adsorbent from iron, which has a high potential to replace commercial adsorbents in wastewater treatment. • Green synthesis of highly efficient magnetite nanoparticles (MNPs-PC) using Pouteria Caimito fruit extract. • MNPs-PC demonstrated a remarkable 96 % removal of Hg(II) within just 15 min under optimized conditions (pH 6.0, 25 °C). • The Langmuir model provided the best fit to the experimental data, with a maximum adsorption capacity of 52.63 mg/g. • The adsorption process was accurately described by a pseudo-second-order kinetic model, indicating a chemisorption mechanism. • Thermodynamic analysis revealed that the removal of Hg(II) is a spontaneous and exothermic process.