S vacancies-introduced chalcopyrite switch radical to non-radical pathways via peroxymonosulfate activation: Vital roles of S vacancies

Abstract

Regulation of peroxymonosulfate (PMS) activation from radical to non-radical pathways is an emerging focus of advanced oxidation processes (AOPs) due to its superiority of anti-interference to complex wastewater. However, the detailed correlation mechanism between the defect structure of the catalyst and the regulation of radicals/non-radicals remains unclear. Herein, natural chalcopyrite (CuFeS₂) with different levels of S vacancies created by a simple NaBH₄ reduction process was employed to explore the above-mentioned underlying mechanism for constructing high efficiency and low cost of catalyst towards AOPs. With the assistance of simulated solar light, S-deficient chalcopyrite (Sv-NCP) exhibited prominent performance for PMS activation. More interestingly, the different degrees of S vacancies regulated the active species from radicals to non-radical ¹O₂, thus showing excellent purification of complex wastewater as well as actual pharmaceutical wastewater. Mechanistic analysis reveals that PMS tends to loss electrons on S vacancies sites and is dissociated into ¹O₂ rather than ·OH/SO₄^·- due to electron deficiency. Meanwhile, the improved adsorption performance makes the degradation sites of pollutants change from solution to surface. Most importantly, Sv-NCP presented excellent detoxication for antibiotic wastewater due to the high selectivity of ¹O₂. This work provides novel insights into the regulation of active species in Fenton-like reactions via defect engineering for high efficiency of pollutant degradation.

Keywords: Chalcopyrite; Fenton-like; NaBH(4); Peroxymonosulfate; S vacancies.