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

This paper presents an accelerated ferrate(VI) (FeO, Fe) oxidation of contaminants in 30 s by adding one-electron and two-electron transfer reductants (R and R). An addition of R (e.g., NHOH, As, Se, P, and NO, and SO) results in Fe initially, while Fe is generated with the addition of R (e.g., SO). R additives, except SO, 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 to Fe. Interestingly, addition of SO (i.e., R) also achieves the enhanced oxidation to 100%. Removal efficiency of TMP depends on the molar ratio ([R]:[Fe] or [R]:[Fe]). Most of the reductants have the highest removal at molar ratio of ∼0.125. A Fe-SO 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. Fe and Fe as the oxidative species in the Fe-SO-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 Fe-SO systems. Significantly, elimination of SO from sulfonamide (i.e., SDM) is observed for the first time.