Removal of heavy metal ions using surface-modified melamine magnetite nanoparticles as effective sorbents prior to determination by atomic absorption spectroscopy

The melamine magnetic nanocomposite adsorbents were synthesized using the hydrothermal method with melamine, ethylene diamine tetraacetic acid, and ۳,۳'-diaminobenzidine. The adsorption efficiencies for the removal of cadmium and lead ions from aqueous solutions were investigated. The adsorbents were characterized using FTIR, high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray (EDX). Batch systems were carried out, and different operation parameters were optimized, including pH, agitation time, and temperature. The concentrations of heavy metal ions were determined with flame atomic absorption spectroscopy (F-AAS). It was observed that maximum removal efficiency was achieved at pH ۸.۰ and ۵.۰, with agitation times of ۶, ۳, and ۱ hours for Cd۲+ and ۲, ۱.۵, and ۱ hours for Pb۲+ respectively. Langmuir, Freundlich, Dubinin–Radushkevich, and Temkin isotherm models were applied, and the results showed that Langmuir was fitted very well for all adsorption systems. According to the linearized Langmuir equation, qmax cadmium and lead ions were ۴۹.۲۶, ۷۶.۹۲and ۲۵۶.۴ mg g-۱ and ۱۸۸.۷, ۲۹۴.۱, and ۵۸۸.۲ mg g-۱ for M@F, M@EDTA@F, and M@EDTA@Am@F, respectively. The kinetic models were conducted to understand the adsorption mechanisms, pseudo-second-order model agreed well with experimental data for cadmium and lead ions overall adsorbents. Adsorption systems results were evaluated by calculating thermodynamic parameters, including enthalpy, entropy, changes in free energy, and activation energy (Ea).

کلیدواژه ها:

Melamine magnetic nanocomposites ، Heavy metal ، Flame atomic absorption spectroscopy ، Isotherm ، Thermodynamic