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Accelerated Oxidation of Organic Contaminants by Ferrate(VI): The Overlooked Role of Reducing Additives
- Feng, Mingbao, Jinadatha, Chetan, McDonald, Thomas J., Sharma, Virender K.
- Environmental science & technology 2018 v.52 no.19 pp. 11319-11327
- X-radiation, additives, artificial sweeteners, drugs, hydroxylamine, nitrites, oxidation, pesticides, reducing agents, sulfadimethoxine, sulfites, sulfur dioxide, thiosulfates, trimethoprim
- This paper presents an accelerated ferrate(VI) (FeⱽᴵO₄²–, Feⱽᴵ) oxidation of contaminants in 30 s by adding one-electron and two-electron transfer reductants (R₍₁₎ and R₍₂₎). An addition of R₍₂₎ (e.g., NH₂OH, Asᴵᴵᴵ, Seᴵⱽ, Pᴵᴵᴵ, and NO₂–, and S₂O₃²–) results in Feᴵⱽ initially, while Feⱽ is generated with the addition of R₍₁₎ (e.g., SO₃²–). R₍₂₎ additives, except S₂O₃²–, show the enhanced oxidation of 20–40% of target contaminant, trimethoprim (TMP). Comparatively, enhanced oxidation of TMP was up to 100% with the addition of R₍₁₎ to Feⱽᴵ. Interestingly, addition of S₂O₃²– (i.e., R₍₂₎) also achieves the enhanced oxidation to 100%. Removal efficiency of TMP depends on the molar ratio ([R₍₁₎]:[Feⱽᴵ] or [R₍₂₎]:[Feⱽᴵ]). Most of the reductants have the highest removal at molar ratio of ∼0.125. A Feⱽᴵ–S₂O₃²– system also oxidizes rapidly a wide range of organic contaminants (pharmaceuticals, pesticides, artificial sweetener, and X-ray contrast media) in water and real water matrices. Feⱽ and Feᴵⱽ as the oxidative species in the Feⱽᴵ–S₂O₃²–-contaminant system are elucidated by determining removal of contaminants in oxygenated and deoxygenated water, applying probing agent, and identifying oxidized products of TMP and sulfadimethoxine (SDM) by Feⱽᴵ–S₂O₃²– systems. Significantly, elimination of SO₂ from sulfonamide (i.e., SDM) is observed for the first time.