Accelerated Oxidation of Organic Contaminants by Ferrate(VI): The Overlooked Role of Reducing Additives

• Published in: Environmental science & technology Vol. 52; no. 19; pp. 11319 - 11327
• Main Authors: Feng, Mingbao, Jinadatha, Chetan, McDonald, Thomas J, Sharma, Virender K
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.10.2018
• Subjects: Additives; Contaminants; Contrast media; Deoxygenation; Electron transfer; Electrons; Iron; Kinetics; Nitrogen dioxide; Organic contaminants; Oxidation; Oxidation-Reduction; Oxygen; Pesticides; Pollutant removal; Sulfadimethoxine; Sulfonamides; Sulfur dioxide; Trimethoprim; Water Pollutants, Chemical; Water pollution; Water Purification
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.8b03770

This paper presents an accelerated ferrate­(VI) (FeVIO4 2–, 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 S2O3 2–) results in FeIV initially, while FeV is generated with the addition of R(1) (e.g., SO3 2–). R(2) additives, except S2O3 2–, 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 S2O3 2– (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–S2O3 2– 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–S2O3 2–-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–S2O3 2– systems. Significantly, elimination of SO2 from sulfonamide (i.e., SDM) is observed for the first time.