pH-dependent mechanisms of sulfadiazine degradation by natural pyrite-driven heterogeneous Fenton-like reactions

• Published in: Journal of environmental management 2024-08, Vol.365, p.121607, Article 121607
• Main Authors: Lin, Xiaoxuan, Hu, Jinwen, Mo, Zhihua, Wang, Zhen, Wang, Ruyi, Liang, Jialin
• Format: Article
• Language: English
• Subjects: Active species pathway; Advanced oxidation; Hydrogen Peroxide - chemistry; Hydrogen-Ion Concentration; Iron - chemistry; Natural pyrite; Peroxides; pH-dependent mechanism; Sulfadiazine - chemistry; Sulfides - chemistry; Water matrix; Water Pollutants, Chemical - chemistry
• ISSN: 0301-4797; 1095-8630; 1095-8630
• DOI: 10.1016/j.jenvman.2024.121607

The development of a natural pyrite/peroxymonosulfate (PMS) system for the removal of antibiotic contamination from water represented an economic and green sustainable strategy. Yet, a noteworthy knowledge gap remained considering the underlying reaction mechanism of the system, particularly in relation to its pH sensitivity. Herein, this paper investigated the impacts of critical reaction parameters and initial pH levels on the degradation of sulfadiazine (SDZ, 3 mg/L) in the pyrite/PMS system, and elucidated the pH dependence of the reaction mechanism. Results showed that under optimal conditions, SDZ could be completely degraded within 5 min at a broad pH range of 3.0–9.0, with a pseudo-first-order reaction rate of >1.0 min−1. The low or high PMS doses could lower degradation rates of SDZ through the decreased levels of active species, while the amount of pyrite was positively correlated with the removal rate of SDZ. The diminutive concentrations of anions exerted minor impacts on the decomposition of SDZ within the pyrite PMS system. Mechanistic results demonstrated that the augmentation of pH levels facilitated the transition from the non-radical to the radical pathway within the natural pyrite/PMS system, while concurrently amplifying the role of •OH in the degradation process of SDZ. This could be attributed to the change in interface electrostatic repulsion induced by pH fluctuations, as well as the mutual transformation between active species. The stable presence of the relative content of Fe(II) in the used pyrite was ensured owing to the reduced sulfur species acting as electron donors, providing the pyrite/PMS system excellent reusability. This paper sheds light on the mechanism regulation of efficient removal of organic pollutants through pyrite PMS systems, contributing to practical application. [Display omitted] •Natural Pyrite/PMS system completely removes sulfadiazine within 5 min.•Unsuitable peroxymonosulfate dose affects levels of reactive oxygen species.•(Non-) free radical pathways and reactive oxygen species are regulated by pH levels.•Stabilisation of Fe(II) valence state in natural pyrite ensures reuse stability.