Photocatalytic Degradation of Rhodamine B via Fe-g-C₃N₄ Activated Sulfate Radical-Based Advanced Oxidation Processes and the Synergistic Mechanism

Fe-doped g-C₃N₄ has been proven to have the potential of visible light photocatalysis, but its catalytic activity of peroxymonosulfate (PMS) is neglected. Herein, the complex advanced oxidation processes of Fe-g-C₃N₄ mediated PMS and visible light photocatalysis was developed, named as Vis/Fe-g-C₃N₄/PMS system, whose effects and synergistic mechanism for decomposing Rhodamine B (RhB) was evaluated. The coupling of sulfate radicals and photocatalysis for RhB degradation showed that the synergistic efficiency (η_Syn) and factor (S_c) were 20.1% and 4.82, respectively, with a degradation efficiency of 99.8%. Iron species dispersed on g-C₃N₄ provided active sites for PMS activation to generate sulfate radicals, simultaneously reduced the forbidden band, and separated the photo-generated charges of g-C₃N₄. h⁺, SO₄^·‾ and ¹O₂ were the main active species, and the increase of ¹O₂ was the cause of the synergistic effect. The possible degradation path of RhB by this coupling system was proposed. Our findings prove that Vis/Fe-g-C₃N₄/PMS system has a great potential to decompose dye wastewater, and also to be an environmental remediation perspective.