Effect of KMnO4 on the migration and transformation of Mn2+ and NH4+-N in electrolytic manganese residue: Autocatalytic system of manganese (Mn2+-MnO2-Mn2+)

Abstract

Electrolytic manganese residue (EMR) leachate contains high concentrations of Mn2+, NH4+-N, and heavy metals, seriously damaging the ecological environment. In this study, the effects of different KMnO4 dosages on the migration and transformation of Mn2+ and NH4+-N in EMR were investigated. The results showed that KMnO4 accelerated the migration and transformation of Mn2+ and NH4+-N. Mn2+ was mainly converted to the new ecologically hydrated MnO2 (NEHMO), which adsorbed Mn2+ and then oxidized it to form new active manganese oxides, thus constructing an autocatalytic oxidation reaction system of manganese (Mn2+-MnO2-Mn2+). A part of NH4+-N adsorbed on the NEHMO surface was catalytically oxidized to NO3–-N and NO2–-N. Mn2+on the EMR surface of the KMnO4 system mainly existed in the form of Mn3+, and the manganese oxides formed by the autocatalytic oxidaton of manganese mainly existed in the EMR system in the Fe-Mn oxidation state and residue state. This study provides theoretical support for developing in-situ remediation technology for EMR in residue sites.