FerrateVI

Ferrate(VI) refers to the iron oxide(anion) with oxidation state +6, commonly written as [FeO4]2-. In salts such as potassium ferrate (K2FeO4) or sodium ferrate (Na2FeO4), this unit exists as a tetrahedral FeO4 core stabilized by a strongly alkaline medium. The ferrate ion is a powerful, water‑insoluble oxidant that is most stable in basic solutions and decomposes when the medium becomes acidic.

Chemically, ferrate(VI) behaves as a strong oxidant. In aqueous base its redox potential is high, and upon reduction it commonly yields ferric iron species (Fe(III)) such as Fe(OH)3, along with water or hydroxide. It can also act as an oxygen source in certain reactions, releasing oxygen during redox processes.

Preparation and stability: Ferrate(VI) is produced by electrochemical oxidation of iron in concentrated alkaline media or by chemical oxidation of Fe3+ or Fe2+ in alkaline solution with oxidants like hypochlorite or ozone under carefully controlled conditions. It is unstable in acidic environments and gradually degrades to Fe(III) hydroxide and oxygen; storage as a solid or in solution requires a basic medium.

Applications: The most prominent use of ferrate(VI) is in water treatment as a powerful oxidant and coagulant precursor. It oxidizes organic contaminants, sulfides and ammonia, and, upon reduction, yields iron(III) hydroxide that helps remove particulates. Its use can reduce the need for additional coagulants and chlorination in some processes. Research continues into higher-valent iron species and new synthesis methods.

Safety: Ferrate(VI) compounds are strong oxidizers and should be handled with care, avoiding mixing with acids or reducing agents; they are typically stored in dry, alkaline conditions to maintain stability.