Overcoming Permanganate Stalling during Electromigration

Electrokinetic experiments were undertaken to transport permanganate (${\mathrm{MnO}}_4^{-}$) through a low permeability porous media. The experiments employed a one-dimensional apparatus in which ${\mathrm{MnO}}_4^{-}$ was electromigrated through a central porous media core. Two outer porous media cores separated the electrode reservoirs from the inner permanganate source and permanganate target reservoirs. By utilizing a pH-isolation technique, whereby electrolysis reactions occurring at electrodes were isolated, uniform and repeatable ${\mathrm{MnO}}_4^{-}$ electromigration was achieved. This result was compared with non-pH-isolated experiments (normal mode), which resulted in a stalled ${\mathrm{MnO}}_4^{-}$ electromigration front. The research also investigated potential stalling mechanisms, including voltage gradient nonlinearity through the central porous media core and the reduction of ${\mathrm{MnO}}_4^{-}$ to ${\mathrm{Mn}}^{2+}$. It was observed that the voltage gradient decreased as a result of ${\mathrm{MnO}}_4^{-}$ stalling; however, it was not considered a stalling mechanism. Results from ${\mathrm{Mn}}^{2+}$ analysis determined that the ${\mathrm{Mn}}^{2+}$ distribution for normal mode experiments extended partially beyond the extent of ${\mathrm{MnO}}_4^{-}$ electromigration; however, competing ions interfered with the analysis and definitive conclusions could not be made. pH-isolated experiments described in this research provide a simple method for implementing electrokinetic in situ chemical oxidation as a groundwater remediation technique where low permeability porous media exists.