Enhanced degradation of Perfluorooctanoic acid from water using AlPMo-X@ZIF-67: Leveraging Al⋅⋅⋅F formation and PMS activation

Abstract

To address the persistent challenge of perfluorooctanoic acid (PFOA) contamination in water, we developed a multifunctional catalyst, AlH₃P₂Mo₁₈-X@ZIF-67 (abbreviated as AlPMo-X@ZIF-67, where X denotes the amount of AlPMo), which integrates aluminum-enhanced fluorine affinity, Dawson-type polyoxometalate-mediated multi-electron redox cycling, and ZIF-67-derived nanoconfinement effects. The catalyst was systematically evaluated for PFOA removal efficiency, key influencing factors (e.g., reaction time, pH, initial concentration, and catalyst dosage), and degradation mechanisms. The results revealed that the synergistic effect of PFOA adsorption and reactive species action was critical for effective degradation. Specifically, Al³⁺ sites immobilized PFOA through Al⋅⋅⋅F coordination, weakening the C–F bond, while Mo⁵⁺/Co²⁺ cooperatively activated peroxymonosulfate (PMS) to generate SO₄⋅^–, ⋅OH, O₂⋅^–, and ¹O₂. Within the nanoconfined environment, PFOA underwent stepwise degradation, involving adsorption-induced C–F bond weakening, decarboxylation, hydroxylation, HF elimination, and chain-shortened hydrolysis. This multi-mechanistic approach enabled 96.4 % PFOA removal within 30 min (10 g/L catalyst, 30 g/L PMS, pH 5, 55 °C) with 48.1 % defluorination in 4 h. Additionally, the reduction in acute and chronic toxicity and the catalyst’s high stability highlighted its potential for practical water treatment applications. This work provided a significant advancement in persistent pollutant remediation by integrating molecular recognition, bond activation, and nanoconfinement catalysis.