Enhanced nitenpyram degradation via hematite/LDH co-catalysis in a peroxymonosulfate/Fe(III)/Fe(II)-EDDS system: Toward sustainable water treatment

Research on peroxymonosulfate (PMS) activation via catalytic processes for degrading trace organic pollutants in aquatic environments has attracted considerable interest. Although iron is widely used in homogeneous advanced oxidation processes (AOPs), its effectiveness in activating PMS remains suboptimal. This study demonstrates that the environmentally benign chelating agent ethylenediamine- N , N ′-dibutyldicarboxylate (EDDS) markedly enhances iron-mediated PMS activation. With six coordination sites, EDDS forms stable five- and six-membered chelate rings with Fe(III)/Fe(II) ions, facilitating efficient PMS activation and leading to complete degradation of NTP. Beyond improving iron's catalytic performance, EDDS also inhibits iron disproportionation, thereby promoting PMS activation and facilitating NTP mineralization. Moreover, the system achieved removal efficiencies exceeding 96 % for tetracycline (TC), ciprofloxacin (CIP), sulfamethoxazole (SMX), and methylene blue (MB) within 35 min. Systematic experiments elucidated the critical role of the Fe(III)/Fe(II) redox cycle in the HeLDH/EDDS/PMS system, highlighting the central involvement of Fe(III) species in the regeneration of Fe(II). Multiple reactive oxygen species, including •OH, SO₄• − , RO•, O₂• − , and 1 O₂, were identified as contributors to NTP degradation. Transformation pathways and mechanistic details of NTP degradation were revealed via mass spectrometry, and toxicity evaluations confirmed a significant reduction in the ecotoxicity of oxidation products. The system also exhibited strong resistance to humic acid interference and effectively degraded multiple organic contaminants, underscoring its potential for sustainable water purification applications.