Enhanced peroxymonosulfate activation by hierarchical porous Fe3O4/Co3S4 nanosheets for efficient elimination of rhodamine B: Mechanisms, degradation pathways and toxicological analysis

Abstract

Fenton-like catalysts have usually superior catalytic activities, however, some drawbacks of ion leaching and difficult-to-recovery limit their applications. In this work, a hierarchical porous Fe₃O₄/Co₃S₄ catalyst was fabricated via a simple phase change reaction to overcome these shortcomings. The introduced iron cooperates with cobalt achieving high-efficiency activation of peroxymonosulfate (PMS) to eliminate Rhodamine B (RhB). The results showed that 0.05 g/L Fe₃O₄/Co₃S₄ and 1 mM PMS could quickly remove 100% of 200 mg/L RhB within 20 min, and the removal rate of RhB remained above 82% after 5 cycles. Moreover, the as-prepared Fe₃O₄/Co₃S₄ possessed a great magnetic separation capacity and good stability of low metal leaching dose. Radical quenching experiments and electron paramagnetic resonance (EPR) techniques proved that sulfate radicals (SO₄^•-) were the dominant reactive oxygen species responding for RhB degradation. X-ray photoelectron spectroscopy (XPS) pointed out that the synergism of sulfur promoted the cycling of Co³⁺/Co²⁺ and Fe³⁺/Fe²⁺, boosting the electron transfer between Fe₃O₄/Co₃S₄ and PMS. Moreover, the degradation pathways of RhB were deduced by combining liquid chromatography-mass spectrometry (LC-MS) analysis and density functional theory (DFT) calculations. The toxicities of RhB and its intermediates were evaluated as well, which provided significant assistance in the exploration of their ecological risks.

Keywords: DFT calculation; Fe(3)O(4)/Co(3)S(4); PMS activation; RhB degradation; Toxicity.