Ferrate (K2FeO4) is a powerful oxidant and up to 3 mol of electrons could be captured by 1 mol of ferrate in the theoretical conversion of Fe­(VI)–Fe­(V)–Fe­(IV)–Fe­(III). However, it is reported that the utilization efficiency of the ferrate oxidation capacity is quite low because of the rapid autodecomposition of intermediate iron species, which negatively influences the potential of ferrate on organic pollutants control. We accidentally found that for the ferrate oxidation of carbamazepine (CBZ), bisphenol S (BPS), diclofenac (DCF), and ciprofloxacin (CIP), the determined reaction rate constants were 1.7–2.4 times lower in phosphate buffer than those in borate buffer at pH 8.0. For the reaction of ferrate with 2,2′-azino-bis­(3-ethylbenzothiazoline-6-sulfonate) (ABTS) at pH 7.0, the determined reaction stoichiometries were 1:1.04 in 100 mM phosphate buffer, 1:1.18 in 10 mM phosphate buffer, and 1:1.93 in 10 mM borate buffer, respectively. The oxidation ability of ferrate seems depressed in phosphate buffer. A kinetic model involving the oxidation of ABTS by Fe­(VI), Fe­(V) and Fe­(IV) species was developed and fitted the ABTS•+ formation kinetics well under different buffer conditions. The results showed that phosphate exhibited little influence on the oxidation ability of Fe­(VI) and Fe­(IV) species, but decreased the specific rate constants of ABTS with Fe­(V) species by 1–2 orders of magnitude, resulting in the outcompeting of Fe­(V) autodecomposition pathway. The complexation between phosphate anions and Fe­(V) species may account for the inhibition effect of phosphate buffer. Considering that many studies regarding ferrate oxidation were carried out in phosphate buffer, the actual oxidation ability of ferrate may be underestimated.

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Many investigations focused on the capacity of ferrate for the oxidation of organic pollutant or adsorption of hazardous species, while little attention has been paid on the effect of ferrate resultant nanoparticles for the removal of organics. Removing organics could improve microbiological stability of treated water and control the formation of disinfection byproducts in following treatment procedures. Herein, we studied ferrate oxidation of p-arsanilic acid (p-ASA), an extensively used organoarsenic feed additive. p-ASA was oxidized into As(V), p-aminophenol (p-AP), and nitarsone in the reaction process. The released As(V) could be eliminated by in situ formed ferric (oxyhydr) oxides through surface adsorption, while p-AP can be further oxidized into 4,4′-(diazene-1,2-diyl) diphenol, p-nitrophenol, and NO 3 − . Nitarsone is resistant to ferrate oxidation, but mostly adsorbed (>85%) by ferrate resultant ferric (oxyhydr) oxides. Ferrate oxidation (ferrate/p-ASA = 20:1) eliminated 18% of total organic carbon (TOC), while ferrate resultant particles removed 40% of TOC in the system. TOC removal efficiency is 1.6 to 38 times higher in ferrate treatment group than those in O 3 , HClO, and permanganate treatment groups. Besides ferrate oxidation, adsorption of organic pollutants with ferrate resultant nanoparticles could also be an effective method for water treatment and environmental remediation.

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