In situ growth of g-C3N4/MIL-101(Fe) on iron mesh to activate persulfate for enhanced removal of methyl orange: mechanism and pathway

Abstract

Organic contamination of water results in significant risks to the biosphere and human health. The treatment of organic pollutants found in effluents urgently requires a green, sustainable, and effective approach. Herein, a straightforward one-step procedure was developed to create a photocatalytic mesh using iron mesh as the substrate and the g-C₃N₄/MIL-101(Fe) heterostructure as the photocatalytic material to activate persulfate (PS) for the removal of methyl orange (MO) from water. Fluorescence stereo microscopy (FSM), scanning electron microscopy (SEM), nitrogen adsorption–desorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD) were used to characterize the morphological and physicochemical properties of the synthesized composites, which confirmed the successful growth of g-C₃N₄/MIL-101(Fe) on the iron mesh. The outstanding PS activation capacity of g-C₃N₄/MIL-101(Fe) promoted electron transfer and accelerated the generation of SO₄˙⁻, resulting in up to 91.05% MO degradation under 60 min of visible light exposure. The removal mechanisms were investigated by quenching experiments and electron spin resonance (ESR), which proved that ˙OH, ˙O₂⁻ and h⁺ contributed to the removal of MO. Moreover, the degradation pathways of MO and the as-formed intermediates were identified by high-resolution mass spectroscopy (HRMS). This study provides a convenient and economical method to build innovative photocatalytic systems for organic pollutant degradation.