Removal of Ammonium and Manganese from Water by MnO_x Media: Establishment of Film Growth Kinetic Model and Chemical Peeling Film Mechanism

Manganese oxide (MnO_x) on the surface of the filter material can be used to effectively remove ammonium (NH₄⁺) and manganese ions (Mn²⁺) from water, but overgrow oxide film gradually shortens backwashing interval after several years of long-term filtration system operation. Different influent pollutant loading result in different durations for chemical peeling film. A growth kinetics model for MnO_x was established by adjusting the different initial concentrations of Mn²⁺ in the influent, which provided a theoretical basis for determining a specific time point for film peeling and recovered the shortened backwashing intervals in the filter columns. The variation in film thickness demonstrated a linear dependence on time, confirming the high accuracy of the kinetics model for film growth. The pseudo-first-order kinetic model better fits among adsorption and oxidation kinetic models of Mn²⁺. Hydrogen peroxide (H₂O₂) was identified as an effective agent in the chemical peeling film process. Hydroxyl radicals, generated by H₂O₂, destroy coordination bonds, producing extremely low solubility (≡MnO₂), which was then removed during the backwashing process.