π-π interaction and electron transfer mediated activation of peroxymonosulfate by quartz sand-supported ZIF-8 composite catalyst for enhanced tetracycline hydrochloride degradation

Tetracycline hydrochloride (TCH), owing to its structural stability and resistance to degradation, has emerged as a typical persistent pollutant in aquatic environments. However, the development of effective and environmentally friendly strategies for the removal of TCH remains highly challenging, owing to limited pollutant enrichment and low catalyst activation efficiency. In this study, a quartz sand-supported ZIF-8 catalyst functionalized with chitosan-derived N-doped carbon (QN@ZIF-8) was rationally constructed: (1) π–π interactions enhanced the adsorption and enrichment of TCH molecules, thereby significantly increasing the probability of contact between pollutants and active sites and (2) its efficient electron transfer channels accelerated the activation of peroxymonosulfate (PMS), facilitating the directional generation of superoxide radicals (•O 2 − ) and singlet oxygen ( 1 O 2 ), thus strengthening the synergistic pathways of both radical and non-radical degradation. Experimental results demonstrated that under optimal conditions (catalyst dosage: 0.5 g/L, PMS: 0.2 g/L, pH ≈ 5.1), QN@ZIF-8 achieved an efficient removal of 90.5% of TCH within 40 min, with an apparent pseudo-first-order rate constant of k = 0.0393 min −1 , which was 2.1 times higher than that of pristine quartz sand. Moreover, the catalyst maintained a removal efficiency above 82.3% after five consecutive cycles and exhibited stable performance in tap water and simulated seawater. Liquid chromatography-mass spectrometry (LC-MS) revealed three predominant TCH degradation pathways. This study not only elucidates the π-system-driven synergistic catalytic mechanism but also offers new insights into material design and theoretical guidance for the efficient remediation of recalcitrant organic pollutants