Fe3S4 nanoparticles wrapped in a g-C3N4 matrix: an outstanding visible active Fenton catalysis and electrochemical sensing platform for lead and uranyl ions

Abstract

Fe₃S₄, commonly known as greigite, is a transition metal chalcogenide and has attracted enormous attention in the field of energy storage and environmental remediation. Herein, a graphitic carbon nitride (g-C₃N₄) encapsulated zero-dimensional Fe₃S₄ nanostructure was synthesized by a solvothermal strategy. The nanocomposite material was characterized in detail by FTIR, PXRD, TGA, FE-SEM, TEM, HRTEM, BET, and XPS techniques. The highly active adsorption and catalytic centers in Fe₃S₄-g-C₃N₄ facilitate (a) the mineralization of methylene blue (MB) dye, (b) electrochemical sensing of Pb²⁺ and UO₂²⁺ ions, and (c) reductive adsorption of UO₂²⁺ ions from aqueous system. Almost complete (>98%) photo-Fenton degradation of MB dye was achieved at pH = 6.0 and by using direct sunlight with the least input of H₂O₂. A glassy carbon electrode (GCE) modified with Fe₃S₄-g-C₃N₄ was fabricated to sense micromolar concentrations of Pb²⁺ and UO₂²⁺ ions in the aqueous medium. The limit of detection for Pb²⁺ and UO₂²⁺ ions was 0.71 and 0.22 μM in the linear concentration range of 1–7 μM and 0.05–8 μM, respectively. Finally, the nanocomposite material was tested for the removal of uranyl ions. The removal of uranyl ions was very rapid, with >95% removed within 30 min of contact time. The adsorption of uranyl ions was described by the Langmuir model with a maximum monolayer adsorption of 185.20 ± 4.3 mg g⁻¹. XPS analysis of U4f and S2p spectra confirmed the charge transfer from the sulfide ion to the uranyl ion, resulting in the reduction of U(VI) to U(IV). The magnetically recoverable Fe₃S₄-g-C₃N₄ nanocomposite showed excellent stability and reusability over multiple catalytic and adsorption cycles.