Waterguide - Manganese
What is manganese?
Manganese belongs to the group of metals (symbol Mn, atomic number 25, atomic mass 55 g/mol) and is found in very low concentrations (950 g/t) in the Earth’s crust (iron is present at 50 g/t). Manganese occurs in land plants, but can also be found in fossilised organic materials. This means manganese is also present in groundwater. Manganese found in groundwater is usually associated with iron.
In what form does manganese occur in the Earth’s crust?
Just like iron, manganese is present in nature as the chemical compound in manganese oxide (MnO with Mn2+). Similar to iron, manganese can be divalent (Mn2+), trivalent (Mn3+) or quadrivalent (Mn4+). The divalent oxidation level is still easily soluble in water. The trivalent and quadrivalent oxidation levels, however, do not dissolve as easily in water. The reason for this is that, with each higher oxidation level, manganese requires very high concentrations of oxygen for oxidation.
How does manganese get into water and what concentrations of manganese does water have?
As manganese is present in plants, which over time turn into mineral oils and fossil materials, manganese inevitably finds its way into bodies of water. Measurements have shown that in 60 % of all groundwater, the concentration of manganese is > 0.05 mg/l.
In surface water, the concentration is 0.14 mg/l. Manganese finds its way into surface water through groundwater flowing into it.
Rainwater can also cause manganese to dissolve out of the Earth’s crust and seep into the groundwater.
Why does manganese have to be removed from water?
Manganese poses a risk to any pipe system as it reacts very easily, especially with oxygen, which can lead to corrosion. It can also cause pipes to become blocked over time.
Uses of manganese
- Alloy component
- Reducing agent in metallurgy
- Glass production
- Zinc-carbon batteries (dry batteries)