Peracetic acid activation by natural chalcopyrite for metronidazole degradation: Unveiling the effects of Cu-Fe bimetallic sites and sulfur species

Abstract

In this work, we reported the effective activation of PAA by natural chalcopyrite (CuFeS₂) to eliminate metronidazole (MTZ) for the first time. The influence of PAA concentration, CuFeS₂ dosage, initial pH, initial MTZ concentration, and water matrix on MTZ decontamination was examined. The effective MTZ degradation (83.92%) was achieved after 30 min under conditions of 460 μM PAA, 4 g L⁻¹ CuFeS₂, and initial pH 3. CuFeS₂ exhibited satisfactory recyclability after five cycles. Hydroxyl radical (OH), organic radicals, and ferryl ion species were proved to exist in the synergistic system based on the scavenging and probe tests, and electron paramagnetic resonance spectrograph, and OH contributed mainly to the MTZ degradation. As expected, surface-bonded Cu(I) and Fe(II) were verified as the main active sites, and surface-bonded Cu(I) had a more significant effect than that of surface-bonded Fe(II). The sulfur atoms of CuFeS₂ could capture protons to form sulfur vacancies, facilitating the exposure of active sites. More importantly, the rich reductive sulfur species in CuFeS₂ could enhance the regeneration of active sites. In addition, major degradation products of MTZ were identified by mass spectrometry, and their toxicity was assessed. The study proposed a new method for combining natural chalcopyrite and peracetic acid for water treatment.