Manganese removal. For manganese removal only, Manganese dioxide (MnO 2) is used as an adsorbent according to the following reaction: Mn + MnO 2 (s) > 2 MnO (s) Manganese oxides are then adsorbed on MnO 2 grains. When all MnO 2 has been consumed, it can be regenerated by sodium hypochlorite.