Photodegradation of para-arsanilic acid mediated by photolysis of iron(III) oxalate complexes

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Organic arsenicals are important environment pollutants due to wide use in livestock and toxicity of degradation products. In this work we report about the efficient photodegradation of the p-arsanilic acid (p-ASA) and its decomposition products in the Fe(III)-oxalate assisted approach under nature-relevant conditions. At neutral pH under near-visible UV irradiation the Fe(III) oxalate complexes generate the primary oxidizing intermediate, [rad]OH radical (the quantum yield of ϕOH ∼ 0.06), which rapidly reacts with p-ASA with high rate constant, (8.6 ± 0.5) × 109 M−1s−1. Subsequent radical reactions result in the complete photooxidation of both p-ASA and basic aromatic photoproducts with the predominant formation of inorganic arsenic species, mainly As(V), under optimal conditions. Comparing with the direct UV photolysis, the presented Fe(III)-oxalate mediated degradation of p-ASA has several advantages: higher efficiency at low p-ASA concentration and complete degradation of organic arsenic by-products without use of short-wavelength UV radiation. The obtained results illustrate that the Fe(III)-oxalate complexes are promising natural photosensitizers for the removal of arsenic pollutants from contaminated waters.

Original languageEnglish
Article number127770
Early online date24 Jul 2020
Publication statusE-pub ahead of print - 24 Jul 2020


  • AOPs
  • Ferrioxalate complex
  • Hydroxyl radical
  • Laser flash photolysis
  • p-ASA
  • Photodegradation

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