Manganese dioxide is an inorganic compound with the formula MnO2. It is a blackish or brown solid. The main ore of manganese, mineral pyrolusite, which is a naturally a occurring manganese species, is attractive for its ability to attract heavy metals, such as iron and manganese as well as for the co-precipitation of arsenic.
Manganese dioxide is produced by mixing a manganous salt with alkali metal permanganate and/or ammonium permanganate. Reaction mixture is then heated to about 150°C in atmosphere containing oxygen until more than 85% of the manganous salt is converted to manganese dioxide and then further elevating the temperature to about 250°C.
Manganese dioxide is used in metallurgy industry as a melting agent in welding fluxes, electrode coatings and casting powders; to prevent absorption of manganese from the metal by the slag; improves the adhesion between the metal and the enamel top layer.
MnO2 is used for dry cell batteries, such as the alkaline battery and the zinc-carbon battery.
In the construction industry, MnO2 is used for the production of sand and cement, as a pigment for concrete.
Manganese dioxide is used as a drying agent; it catalyzes the oxidation of oils in paints and varnishes.