Efficient removal of Pb(ii) from water using magnetic Fe3S4/reduced graphene oxide composites

Abstract

Nanostructured metal sulfides hold great promise for adsorption and catalysis applications, but it remains challenging for them to achieve highly efficient decontamination and facile separation of heavy metal ions from water. Herein, Fe₃S₄/reduced graphene oxide composites (Fe₃S₄/rGO) were successfully prepared and utilized for the removal of Pb(II) from water. Uniform Fe₃O₄ nanoparticles were firstly dispersed on the rGO, and employed as sacrificial materials for a facile sulfuration approach. This gave rise to the fabrication of Fe₃S₄ nanoparticles (Fe₃S₄ NPs) with an average size of 14.3 nm. The resultant Fe₃S₄/rGO presented an evidently greater adsorption capacity (285.71 mg g⁻¹) and advantages in driving fast adsorption of Pb(II) in comparison with Fe₃O₄/rGO (106.27 mg g⁻¹). A remarkable selectivity for Pb(II) was achieved in the presence of coexisting cations and anions, and the addition of humic acid promoted the removal of Pb(II) by Fe₃S₄/rGO. The enhanced performance of Fe₃S₄/rGO was mostly facilitated by synergetic contributions of the strong and selective Pb–S interactions between Pb(II) and small Fe₃S₄ NPs associated with the surface adsorption. Remarkably, a single treatment of smelting wastewater with Fe₃S₄/rGO effectively reduced Pb(II) concentration below the drinking water standard that is recommended by the U.S. Environmental Protection Agency, along with a surprisingly high removal efficiency toward arsenic (96.18%). However, Fe₃O₄/rGO merely exhibited a low removal rate of 29.59% for Pb(II). The efficient removal performance of Fe₃S₄/rGO exhibited its great potential in the remediation of heavy metal polluted water via simultaneously taking advantage of magnetic properties and a high affinity for heavy metals.