Stabilization of potassium permanganate particles with manganese dioxide

A new potassium permanganate reagent with slow-release properties was designed and tested for possible application in in situ chemical oxidation. For this purpose, MnO2-coated KMnO4 particles (MCP) were prepared by partial reduction of solid KMnO4 using the acid-catalyzed reaction with n-propanol or the comproportionation of Mn(VII) and Mn(II) in n-propanol as reaction medium. Column tests showed that, for MCP with a residual KMnO4 fraction of 70 wt%, the duration of permanganate release under flow-through conditions was prolonged by a factor of 10 compared to untreated KMnO4. While KMnO4 is too soluble to be used in reactive barriers, MCP could be introduced into the aquifer by filling of trenches or boreholes; this would allow a prolonged passive dosing of permanganate into the flowing groundwater. In addition, experiments were conducted in order to determine the oxidation capability of native KMnO4 particles and MCP in CH2Cl2, a representative non-polar non-aqueous phase liquid (NAPL). It may be possible to utilize the significantly higher reactivity of MCP under these conditions for the design of slow-release permanganate particles for NAPL source treatment.

► Synthesis of MnO2 coating by partial reduction of KMnO4 (MCP).
► Obtained new oxidant with slow-release properties.
► Good oxidation activity of MCP under heterogeneous conditions.
► MCP as a new tool for NAPL source treatment.