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Permanganate Neutralizing Solutions

May 8th, 2018

The family of RemOx® S ISCO reagent (potassium permanganate) and RemOx® L ISCO reagent (sodium permanganate) products are commonly used for the in situ chemical oxidation of chlorinated solvents such as perchloroethylene (PCE), trichloroethylene (TCE), and their daughter products. Both permanganates are strong oxidizers and require careful handling. During the course of the application of permanganate, there is the chance that the neutralization and/or disposal of excess permanganate may be required. Regardless of whether the need is for the clean up and removal of a small spill, the neutralization of excess permanganate solution from equipment, the rinse water produced when cleaning buckets and drums or any other activity where excess permanganate may cause a concern, following a few simple rules will ensure that the process will be safe and easy. If neutralization is required because of a spill, and the spill is a dry RemOx S product, it can be swept or shoveled and transferred to a clean, metal container. Dilute the product with water, and mix the solution until all the crystals are dissolved prior to neutralization. If the spill is a liquid RemOx S solution, contain the liquid by diking or collecting and neutralize. If the spill is RemOx L, the first step is to contain or collect the spill. Prior to any neutralization, sodium permanganate MUST BE DILUTED with water to a concentration of 6% or less. Once the product has been diluted, it can be safely neutralized.

Chemical Reactions

The family of RemOx® S ISCO reagent (potassium permanganate) and RemOx® L ISCO reagent (sodium permanganate) products are commonly used for the in situ chemical oxidation of chlorinated solvents such as perchloroethylene (PCE), trichloroethylene (TCE), and their daughter products. Both permanganates are strong oxidizers and require careful handling. During the course of the application of permanganate, there is the chance that the neutralization and/or disposal of excess permanganate may be required. Regardless of whether the need is for the clean up and removal of a small spill, the neutralization of excess permanganate solution from equipment, the rinse water produced when cleaning buckets and drums or any other activity where excess permanganate may cause a concern, following a few simple rules will ensure that the process will be safe and easy. If neutralization is required because of a spill, and the spill is a dry RemOx S product, it can be swept or shoveled and transferred to a clean, metal container. Dilute the product with water, and mix the solution until all the crystals are dissolved prior to neutralization.

If the spill is a liquid RemOx S solution, contain the liquid by diking or collecting and neutralize. If the spill is RemOx L, the first step is to contain or collect the spill. Prior to any neutralization, sodium permanganate MUST BE DILUTED with water to a concentration of 6% or less. Once the product has been diluted, it can be safely neutralized. There are a number of different chemicals that will neutralize permanganate solutions. Below are some of the commonly used chemicals, their reactions with permanganate, and the stoichiometric requirements.

Sodium thiosulfate
8 KMnO4 + 3 Na2S2O3 + H2O 3 K2SO4 + 3 Na2SO4 + 8 MnO2 + 2 KOH
Weight Ratio: 0.375 parts Na2S2O3 : 1 part KMnO4

Sodium bisulfite (meta)
2 KMnO4 + 3 NaHSO3 + H2O 3 NaHSO4 + 2 MnO2 + 2 KOH
Weight Ratio: 1 part NaHSO3 : 1 part KMnO4

Manganous sulfate

2 KMnO4 + 3 MnSO4 + 2 H2O K2SO4 + 2 H2SO4 + 5 MnO2
Weight Ratio: 1.43 parts MnSO4 : 1 part KMnO4

Hydrogen peroxide
2 KMnO4 + 4 H2O2 2 KOH + Mn2O3 + 3 H2O + 4 O2
Weight Ratio: 0.43 parts H2O2 : 1 part KMnO4
Note: at pH <9, more may be needed due to self decomposition of peroxide

Citric Acid
6 KMnO4 + C6H8O7 + 6H+ 6 MnO2 + 6 CO2 + 7 H2O + 6 K+
Weight Ratio: 0.20 parts C6H8O7 : 1 part KMnO4

Ascorbic Acid
20 KMnO4 + 3 C6H8O6 + 20 H+ 20 MnO2 + 18 CO2 + 22 H2O + 20 K+
Weight Ratio: 0.167 part C6H8O6 : 1 part KMnO4

Other Neutralizing Solutions

In addition to the previously mentioned neutralizing agents, permanganate solutions can be neutralized using the following:

Cleaning/Neutralizing Solution
This solution consists of products that can be purchased from a local food or drug store. This solution is especially effective for removal of brown stains on skin; however, it has also been used as a neutralization solution for small spills. It would not be economical for anything but the smallest volumes of dilute permanganate.

30 parts water: 40 parts white vinegar: 30 parts 3% hydrogen peroxide

Sugar
White sugar is also readily available and can be used to neutralize permanganate solution. The reaction of permanganate and sugar is relatively slow, taking about 30 minutes for a complete reaction. The by-product of the reaction is typically a gelatinous residue.

Sugar (C12H22O11) Weight Ratio: 0.18 parts sugar : 1 part KMnO4

Summary

The following chart summarizes the amount of neutralizing agent required, in pounds, to neutralize one pound of permanganate.

permanganate neutralizing solutions

•Never use any of these solutions on sensitive tissues such as eyes, mucous membranes, open wounds, etc.

•Do not add directly to concentrated permanganate solutions.

•Dilute the permanganate solution to less than 6% before using any of these solutions.

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