Oxidation of Fe(III) to Fe(VI) by ozone in alkaline solutions

The action of ozone on a suspension of Fe(III) hydroxide in alkaline solutions was studied by the spectrophotometric method. A partial conversion of Fe(III) to Fe(VI) is observed at Fe(III) concentrations exceeding 2 mmol l−1. The tenfold increase of the initial Fe(III) concentration raises the Fe(VI) yield by a factor of 2–3. The mechanism of the process includes the decomposition of ozone with the formation of ozonide ions, which oxidize Fe(III) up to Fe(IV), Fe(V), and Fe(VI) in parallel with their conversion to O2− and HO2−. Fe(VIII) is not formed.