KMnO4 can be prepared from K2MnO4 as per the reaction: 3MnO4²⁻ + 2H2O ⇌ 2MnO4⁻ + MnO2 + 4OH⁻. The reaction can go to completion by removing OH⁻ ions by adding: CO2, SO2, HCl, KOH

The reaction for the oxidation of manganate ion to permanganate ion can go to completion by removing hydroxide ions by adding CO2. The added CO2 reacts with the hydroxide ions to form bicarbonate ions (HCO3⁻) or carbonate ions (CO3²⁻), thus shifting the equilibrium to the right and favoring the formation of permanganate ions (MnO4⁻).