High performance of fixed-bed filtration for reagentless oxidative manganese removal

Manganese mud (MnM) is a manganese oxide petal-like nanostructured precipitate that accumulates on the inner surface of pipes transferring reclaimed effluent from the Shafdan soil aquifer treatment system to irrigation fields in southern Israel. It was found that Mn²⁺ adsorbs on the MnM sediment, and under aerobic conditions, rapid Mn(II) oxidation takes place. The MnM exhibited superior Mn(II) adsorption capacity compared to other commercially available manganese oxide catalysts. A filter loaded with anthracite-supported MnM was developed and used as a highly efficient, reagentless catalyst for the continuous oxidative removal of dissolved Mn. A 10-13 m³·h^-1 pilot plant was constructed for Mn removal from Mn-rich effluent by atmospheric oxygen oxidation. The system operated continuously for more than two years with minimal maintenance, without oxidative regeneration. No ripening period was required, and the fixed bed exhibits exceptionally high catalytic efficiency. The proposed filter is superior to synthetic supported manganese oxide reactors because it does not require periodic regeneration by strong oxidizers; it is superior to filtration units for manganese removal because it does not require ripening time. A possible explanation for the superior catalytic activity based on the delicate, two-dimensional structure of MnM is presented.