Sustainable industrial wastewater purification: Fabrication of magnetic γ-Fe2O3@NiFe-layered double hydroxides and efficient Rhodamine B degradation without light irradiation

Addressing the environmental impact of heavy metal ions and organic dye pollution from industrial processes is a critical challenge for sustainable development. Herein, an innovative approach is reported to sustainable purification of industrial wastewater through the synthesis of magnetic γ-Fe 2 O 3 @NiFe-layered double hydroxides (γ-Fe 2 O 3 @NiFe-LDHs) from wastewater containing various heavy metal ions, which are recovered by a magnetic field and then applied to Rhodamine B (RhB) wastewater treatment. The synthesized γ-Fe 2 O 3 @NiFe-LDHs were proved to possess LDHs characteristics, as confirmed through a comprehensive suite of techniques including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and electron paramagnetic resonance (EPR) analysis. Remarkably, these γ-Fe 2 O 3 @NiFe-LDHs demonstrate exceptional efficacy in removing high concentrations of heavy metal ions (including Fe, Ni, Cr, Cu, Ca, Al, and Mg), as well as Mn, achieving removal efficiencies of 99.99 % and 97.89 %, respectively, through highly super-stable mineralization process. Meanwhile, the integration of multiple transition metals (Ni, Fe, Cr, Cu, and Mn) within the NiFe-LDHs laminates enables critical electronic cycling for RhB degradation via Fe-based Fenton-like reactions, achieving both cost-effective and highly efficient catalytic performance. Specifically, these γ-Fe 2 O 3 @NiFe-LDHs facilitated the degradation of RhB (100 mL, 50 mg/L) to an impressive 96.44 % without any light irradiation, and notably retained catalytic activity across several reused cycles. This environmentally friendly approach promotes sustainable treatment among different industrial wastewaters and offers great potential for the development of multilevel resource utilization and green environmental management.