One-step synthesis of water-dispersible cysteine functionalized magnetic Fe₃O₄ nanoparticles for mercury(II) removal from aqueous solutions

Graphical abstract: Using Fe²⁺ as precursors, air as oxidant and cysteine as protectant, this novel cysteine functionalized Fe₃O₄ magnetic nanoparticles (Cys-Fe₃O₄ MNPs) was facilely one-pot synthesized at room temperature by oxidation–precipitation method with the assistance of sonication. Then the Cys-Fe₃O₄ MNPs were demonstrated as an inexpensive and quite efficient magnetic nano-adsorbent for as high as 95% Hg(II) removal efficiency. These results indicated that Cys-Fe₃O₄ MNPs is a potentially attractive material for the removal of Hg(II) from water. - Highlights: • A simplified one-step synthesis method of superparamagnetic Cys-Fe₃O₄ MNPs was developed. • It was synthesized at room temperature by oxidation-precipitation method with the assistance of sonication. • It was demonstrated as an inexpensive and quite efficient magnetic nano-adsorbent for Hg(II) removal. - Abstract: Cysteine functionalized Fe₃O₄ magnetic nanoparticles (Cys-Fe₃O₄ MNPs) were prepared facilely for Hg(II) removal from aqueous solutions. Using Fe²⁺ as precursors, air as oxidant and Cys as protectant, this novel material was one-pot synthesis at room temperature by oxidation–precipitation method with the assistance of sonication. The MNPs were characterized by TEM, VSM, FTIR, X-ray powder diffraction analysis (XRD) and TGA methods. Under the optimum experimental conditions, the removal efficiency was as high as 95% and the maximum sorption capacity is found to be 380 mg/mol for Hg(II). Study on adsorption kinetics shows that adsorption of Hg(II) onto Cys-Fe₃O₄ MNPs follows pseudo-first-order kinetic model and the adsorption rate constant was 0.22 min⁻¹. Additionally, the Hg(II)-loaded Cys-Fe₃O₄ MNPs could be easily regenerated up to 95% using 1.0 M acetic acid. These results indicated that Cys-Fe₃O₄ MNPs is a potentially attractive material for the removal of Hg(II) from water