Chemical oxidation with Permanganate - in situ
Permanganate (MnO4-) oxidation is the most common and most used of all chemical oxidation techniques. Compared with other oxidants such as ozone or hydrogen peroxide, permanganate has a lower oxidation potential but it is more stable and more persistent in soils. As a result, it can migrate by diffusive and advective processes (FRTR, 2002), giving it a greater zone of influence. Oxidant delivery systems often employ vertical or horizontal injection wells using pressure to force the oxidant into the subsurface.
Permanganate is available in liquid (e.g. NaMnO4) or crystalline form. Permanganate salt is generally potassium permanganate (KMnO4), but calcium or magnesium salts are also available. The injection solution is denser than water, which facilitates the vertical movement of the oxidant through the contaminated matrix, and improves contact between the oxidant and the contaminant. Permanganate oxidation is effective over a pH range of 3.5 to 12, but specific oxidation reactions are pH dependent. The oxidation reactions can lower the pH if the system is not adequately buffered. Degradation rates with permanganate also depend on temperature, organic matter content and reduced mineral species.
Permanganate oxidation is suitable for all substances that can be oxidized, such as organic compounds. Compared to the ex situ permanganate chemical reaction, the in situ technique does not generate large volumes of waste material, and is effective over a shorter period of time.
- 4.4 Chemical Oxidation - FRTR Remediation Technologies Screening Matrix and Reference Guide, Version 4.0
- Technical and Regulatory Guidance for In situ Chemical Oxidation of Contaminated Soil and Groundwater - ITRC pdf
- In-situ Chemical Oxidation—Permanganate and Fenton's Reagent - Techtree - CPEO org
Recommended Analyses for Detailed Characterization
- Contaminant concentrations Footnotes1
- Organic matter content
- Concentration of oxidant-consuming substances Footnotes2
- Reaction parameters Footnotes3
- Soil granulometry
- Presence of non-aqueous phase liquids (NAPLs)
Recommended Trials for Detailed Characterization
- Evaluation of the matrix oxidant demand
- Vapour survey
- Evaluation of the radius of influence
- Evaluation of operating pressure/vacuum
- Tracer tests
Other Information Recommended for Detailed Characterization
- Contaminant delineation (area and depth)
- Presence of environmental receptors Footnotes4
- Soil stratigraphy
- Characterization of the hydrogeological system Footnotes5
- Identification of preferential pathways
- Volume of contaminated material to treat
- Conceptual site model with hydrogeological and geochemical inputs
Pilot scale field tests are recommended for selecting the type and position of injection wells, establishing the radius of influence of the injection wells and to calculate optimal permanganate injection rates
- Overall effective pH range of 3.5 to 12, narrower ranges for specific oxidation reactions
- Specific for the degradation of polycyclic aromatic hydrocarbons (PAHs), chlorinated aliphatics such as perchloroethylene (PCE), trichloroethylene (TCE), dichloroethylene (DCE), and vinyl chloride (VC) and other organic contaminants
- Soil permeability must be sufficient to allow oxidant migration. The optimum permeability ranges from 0.25 to 0.5 pore volume/day.
- In situ
- Ex situ
- Dissolved contamination
- Free Phase
- Residual contamination
State of Technology
| Aliphatic chlorinated hydrocarbons |
Monocyclic aromatic hydrocarbons
| Non metalic inorganic compounds |
Policyclic aromatic hydrocarbons
- < 1 year
- 1 to 3 years
- 3 to 5 years
- > 5 years
Secondary By-products and/or Metabolites
Chemical oxidation with permanganate produces carbon dioxide (CO2), water (H2O), and inorganic chloride during the oxidation of chlorinated organics. Degradation of contaminants by permanganate oxidation may produce toxic secondary by-products, depending on the nature of the contaminants. Volatile compounds may also be released. Oxidation with permanganate can also create manganese oxide deposits (MnO2) which can reduce the permeability of the aquifer.
Limitations of the Technology
- Permanganate oxidation technology is temperature and pH dependent
- Soil permeability and matrix heterogeneity limit the application of the technology
- Potential for the oxidant to only move through preferential pathways
- Potential for mobilization of redox-sensitive compounds, such as metals
- Reduction in soil permeability during treatment due to CO2 entrapment, precipitation of KMnO4, etc.
- Mobilisation of certain metals
- Presence of oxidant consumers in the soil matrix that could reduce oxidant efficiency
- Costs can quickly increase if large quantities of permanganate are required due to high concentrations of non-target oxidant consuming compounds
- Handling of a hazardous oxidant and controlling of hazardous permanganate dust
- The permanganate oxidation reactions may disrupt other remediation techniques, such as natural reductive dehalogenation
Complementary Technologies that Improve Treatment Effectiveness
- Non aqueous phase liquids (NAPLs) present in the contaminated matrix must be removed prior to applying this technique
- Radio-frequency heating, resistive heating, or surfactant technologies enhance the in situ permanganate oxidation process
Required Secondary Treatments
Controlling fugitive vapours that may be produced from the heat of reaction.
Application examples of chemical oxidation with permanganate are available in the following document:
- Technical and Regulatory Guidance for In Situ Chemical Oxidation of Contaminated Soil and Groundwater - ITRC pdf
According to the FRTR (2002), in situ chemical oxidation techniques can achieve high treatment efficiencies (e.g. > 90 percent) for unsaturated chlorinated aliphatics (e.g. trichloroethylene [TCE]) with very fast reaction rates (90 percent destruction in minutes).
- U.S. Environmental Protection Agency. 2006. Engineering Issue- in situ Chemical Oxidation. EPA 600-R-06-072
- U.S. Environmental Protection Agency (EPA). 2004. How to Evaluate Alternative Cleanup Technologies for Underground Storage Tank Sites: A Guide for Corrective Action Plan Reviewers. EPA 510-B-94-003; EPA 510-B-95-007; and EPA 510-R-04-002.
- Interstate Technology Regulatory Council (ITRC). 2005. Technical and Regulatory Guidance for in situ Chemical Oxidation. Second Edition.
Josée Thibodeau, M.Sc
National Research Council
David Morin, Ph.D
Latest update provided by:
Karine Drouin, M.Sc.
National Research Council
Return to footnote1 Contaminant concentrations: Identification and concentration of all contaminants (sorbed, dissolved, and free phase).
Return to footnote2 Oxidant-consuming substances include natural organic matter and reduced minerals, as well as carbonate and other free radical scavengers.
Return to footnote3 Reaction parameters includes : kinetic, stoichiometry, and thermodynamic parameters.
Return to footnote4 Presence of potential environmental receptors, above and below ground infrastructure, and the risk of off-site migration.
Return to footnote5 Complete characterization of the hydrogeological system includes: the depth and thickness of the aquifer, the direction and speed of the groundwater flow, etc.
- Date modified