Characteristics and applications of controlled–release KMnO 4 for groundwater remediation

Abstract

In situ chemical oxidation (ISCO) using potassium permanganate (KMnO 4) has been widely used as a practical approach for remediation of groundwater contaminated by chlorinated solvents like trichloroethylene. The most common applications are active flushing schemes, which target the destruction of some contaminant source by injecting concentrated permanganate ( MnO 4 - ) solution into the subsurface over a short period of time. Despite many promising results, KMnO 4 flushing is often frustrated by inefficiency associated with pore plugging by MnO 2 and bypassing. Opportunities exist for the development of new ISCO systems based on KMnO 4. The new scheme described in this paper uses controlled–release KMnO 4 (CRP) as an active component in the well-based reactive barrier system. This scheme operates to control spreading of a dissolved contaminant plume. Prototype CRP was manufactured by dispersing fine KMnO 4 granules in liquid crystal polymer resin matrix. Scanning electron microscope data verified the formation of micro-scale (ID = 20–200 μm) secondary capillary permeability through which MnO 4 - is released by a reaction-diffusion process. Column and numerical simulation data indicated that the CRP could deliver MnO 4 - in a controlled manner for several years without replenishment. A proof-of-concept flow-tank experiment and model simulations suggested that the CRP scheme could potentially be developed as a practical approach for in situ remediation of contaminated aquifers. This scheme may be suitable for remediation of sites where accessibility is limited or some low-concentration contaminant plume is extensive. Development of delivery systems that can facilitate lateral spreading and mixing of MnO 4 - with the contaminant plume is warranted.