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oai:figshare.com:article/34021309 2026-09-29T05:05:57Z category_1 category_4 category_8 category_272 category_873 category_734 portal_63 item_type_6 month_year_09_2026

Chelating Agent-Mediated Pathways for PFOA Degradation and Defluorination in Fe₃O₄‑Catalyzed H₂O₂ Reactions Yi-Wei Biao (25135327) Bai-Quan Cheng (25135330) Wan-Ru Chen (1996771) Biophysics Biochemistry Microbiology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Biological Sciences not elsewhere classified widely used per total fluorine ). optimizing catalytic systems maintains higher reactivity chain perfluorocarboxylic acids 2 %, respectively similar degradation behaviors identified pathways may pfhxs ), indicating five chelating agents reactions perfluorooctanoic acid including perfluorooctanesulfonic acid >- methyliminodiacetic acid governing degradation pathways slow reaction rate mechanistic studies revealed 3 +</ sup improved pfoa degradation enhancing pfoa degradation 2 +</ sup 3 </ sub 2 </ sub 4 </ sub sup >–</ sup 3 %) pfoa degradation n </ k </ Perfluorooctanoic acid (PFOA), a widely used per- and polyfluoroalkyl substance, is persistent in the environment and linked to health concerns, leading to strict regulations and the need for remediation strategies. This study explores PFOA degradation using magnetite (Fe₃O₄)-catalyzed H₂O₂. To address the slow reaction rate of heterogeneous catalysts, five chelating agents (CAs) were tested as enhancements to investigate their influence on the Fe₃O₄–H₂O₂ process. Central composite design results showed that increasing H₂O₂ concentrations (0 to 2 M) improved PFOA degradation, but Fe₃O₄ needed to remain within 3–5.5 g/L for optimal performance. Even under the optimized conditions, only 15% of PFOA was degraded after 48 h. However, adding chelating agents significantly improved degradation rates. Ascorbic acid (AA) and oxalic acid (OX) were the most effective, enhancing PFOA degradation to 81.2% and 77.2%, respectively, compared to citric acid (27.3%) > phosphonoacetic acid (23.4%) > <i>N</i>-methyliminodiacetic acid (12.1%). Mechanistic studies revealed that AA accelerates the initial reaction by reducing Fe³⁺ to Fe²⁺, increasing the initial-stage <i>k</i>_{obs,0–10min} from 0.0077 to 0.0304 min^–1. In contrast, OX facilitates the rapid dissolution of Fe₃O₄, forming a complex with Fe²⁺ that improves H₂O₂ utilization and significantly accelerates the reaction at the initial stage. The observed <i>k</i>_obs,0–2min and <i>k</i>_{obs,2–10min} are 0.4392 and 0.0189 min^–1, respectively. After approximately 10–20 min, the oxidized product of AA, despite losing its reducing capacity, continued to dissolve Fe₃O₄. This maintains higher reactivity in the Fe₃O₄–H₂O₂-AA reaction (<i>k</i>_{obs,10–180min} = 0.0050 min^–1). In contrast, the Fe₃O₄–H₂O₂–OX reaction almost stopped (<i>k</i>_{obs,10–180min} = 0.0009 min^–1) due to Fe³⁺–OX complex formation. Quenching experiments identified superoxide radicals as the key reactive species responsible for PFOA degradation. Product analysis further revealed that AA facilitated partial mineralization, as evidenced by the generation of short-chain perfluorocarboxylic acids and measurable fluoride release (∼50% of total fluorine). In contrast, F^– was not detectable in the OX system, suggesting limited defluorination despite substantial PFOA degradation. Similar degradation behaviors were also observed for other PFAS, including perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS), indicating that the identified pathways may be applicable to a broader range of PFAS. These findings highlight the critical role of Fe²⁺ availability in governing degradation pathways and provide insights for optimizing catalytic systems for PFAS remediation. 2026-09-29T00:00:00Z Text Journal contribution 10.1021/acsestwater.6c00506.s001 https://figshare.com/articles/journal_contribution/Chelating_Agent-Mediated_Pathways_for_PFOA_Degradation_and_Defluorination_in_Fe_sub_3_sub_O_sub_4_sub_Catalyzed_H_sub_2_sub_O_sub_2_sub_Reactions/34021309 CC BY-NC 4.0