ISOTEC’s modified Fenton’s reagent (MFR) is based on the fundamental principles of Fenton’s chemistry. Henry J.H. Fenton was a British chemist who first demonstrated the use of Fenton’s chemistry in 1894, through the oxidation of tartaric acid using a soluble iron-catalyzed decomposition of dilute hydrogen peroxide under acidic conditions. Our MFR process was developed with the fundamental goal of enhancing in-situ treatment of soil and groundwater contamination using Fenton’s chemistry while mitigating the drawbacks associated with application of Fenton’s reagent in its conventional form (such as acidic pH, limited catalyst mobility, etc). The process generates powerful free radicals when the catalyst reacts with hydrogen peroxide. The principal chemical reaction associated with the modified Fenton’s process is provided below:
H2O2 + Fe2+ → OH● + OH– + Fe3+
Where:
H2O2 = Hydrogen Peroxide
Fe2+ = Ferrous Ion
Fe3+ = Ferric Ion
OH● = Hydroxyl Radicals
OH– = Hydroxide Ion
In addition to the initial reaction that produces hydroxyl radical oxidants, the modified Fenton’s process also produces superoxide radical and hydroperoxide anion reductants through additional chain propagation reactions. The perhydroxyl radical is known to be a weaker reductant compared to superoxide radical and hydroperoxide anions.
H2O2 + OH● → HO2●+ H2O
HO2● → H+ + O2●–
HO2●+ O2●– → HO2– + O2
Where:
O2•- = Superoxide Radical Anion
HO2– = Hydroperoxide Anion
HO2• = Perhydroxyl Radical
The co-existing oxidation-reduction reactions associated with a modified Fenton’s process promote enhanced desorption and degradation of recalcitrant compounds. These include compounds such as carbon tetrachloride and chloroform, which were previously considered untreatable by Fenton’s chemistry.
ISOTEC’s modified Fenton’s Reagent is quickly emerging as the leading remedial technique of the 21st century. However, if you are familiar with how conventional Fenton’s is most often applied, using strong acids and high reagent concentrations under pressure, then you are familiar with its shortcomings. ISOTEC’s MFR was specifically designed to overcome these problems, which often include incomplete treatment, explosive reactions, organic vapor generation and contaminant migration.
The MFR process consists of injecting patented chelated iron catalysts and stabilized hydrogen peroxide into contaminated aquifers. Our patented catalysts and stabilizers allow reagents at background neutral pH conditions to be effectively distributed within the aquifer, destroying contaminants in saturated soil and groundwater while minimizing generation of organic vapors or high temperatures. As compared to conventional Fenton’s Reagent, which require acidic conditions (pH~3), MFR is effective at neutral (pH~7) conditions. This is an important consideration in full-scale application, since acidifying an aquifer is typically impractical. Additionally, the production of superoxide, the driving reaction for contaminant reduction and desorption, is inhibited under acidic conditions.
COMPARISON WITH OTHER PEROXIDE-BASED TECHNOLOGIES
| Technology Features | Hydrogen Peroxide | Classic Fenton’s Reagent | Modified Fenton’s Reagent |
|---|---|---|---|
| Aquifer Acidification | No | Yes | No |
| Hydroxyl Radical Production | Limited | Yes, if pH < 3 | Yes |
| Superoxide Radical Production | No | Limited | Yes |
| Controlled Reaction | No | No | Yes |
| Bioremediation Stimulation | Yes | Limited | Yes |