Excellent capture of Pb(II) and Cu(II) by hierarchical nanoadsorbent Fe3O4@SiO2@PAA-SO3H: A combined experimental and theoretical study

Abstract

A novel magnetic nanoadsorbent (Fe₃O₄@SiO₂@PAA-SO₃H) was synthesized by grafting acrylic acid and sulfonic group to Fe₃O₄@SiO₂ using a facile cross-link technology. The adsorbent presented water-stability and biocompatibility in wastewater, which exhibited high-selectivity capture for Pb(II) and Cu(II) of 182.5 mg/g and 250.7 mg/g, respectively, at pH 6.0. Furthermore, the adsorption-desorption processes show that nanoadsorbent still retains high uptake capacity after 6 cycles, revealing structural stability and advanced recycling. Effects from other ions existed weak interference in removal of Pb(II) and Cu(II). Meanwhile, the mechanism was further analyzed from both electrostatic potential (ESP) and average local ionization energy (ALIE) based on the density functional theory (DFT). The results indicate that interaction among nanoadsorbent and heavy metal ions is bridged by oxygen active sites. As the Fe₃O₄@SiO₂@PAA-SO₃H adsorbent is a hierarchical, highly water-dispersible and biocompatible adsorbent, it is a potential new treatment option for wastewater.

Keywords: Density functional theory; Electrostatic interaction; Hierarchical nanoadsorbent; Water purification mechanism.