By Sean Butner – Updated Mar 24, 2022

Fenton’s reagent is a powerful oxidizing system composed of hydrogen peroxide (H₂O₂) and ferrous iron (Fe²⁺). It generates highly reactive hydroxyl radicals that break down a wide range of organic pollutants, including chlorinated solvents and phenols. Below is a detailed, safety‑first protocol for preparing and using this reagent in a laboratory setting.

Safety Precautions

• Wear chemical‑resistant gloves, a lab coat, and safety goggles.
• Work in a well‑ventilated fume hood to avoid inhalation of H₂O₂ vapors.
• Keep a fire extinguisher and neutralizing agent (e.g., sodium thiosulfate) nearby.
• Use only pharmaceutical‑grade or analytical‑grade reagents to avoid impurities that could interfere with the reaction.

Step 1: Acidify the Reaction Medium

Adjust the solution’s pH to the optimal range of 3.0–5.0 using a suitable buffer (e.g., acetate or citrate). Verify the pH with a calibrated pH meter and repeat the measurement until the value stabilizes.

Step 2: Add Ferrous Sulfate

Introduce an aqueous solution of ferrous sulfate (FeSO₄·7H₂O) to the acidified medium. The typical concentration is 0.01–0.05 M Fe²⁺, but this can be tuned based on the contaminant load.

Step 3: Introduce Hydrogen Peroxide

Slowly add a 30–35 % hydrogen peroxide solution while continuously stirring. Monitor the pH after each addition; adjust the H₂O₂ addition rate to maintain the pH between 3.0 and 6.0. Once the desired ratio of H₂O₂ to Fe²⁺ (commonly 5–10:1) is achieved, stop the addition.

Things Needed

• Buffer solution (pH 3–6)
• Ferrous sulfate (FeSO₄·7H₂O)
• Hydrogen peroxide (30–35 %)
• Calibrated pH meter
• Stirring apparatus and fume hood

For more detailed safety guidelines, consult the ATSDR Toxic Substances Portal and the EPA’s Fenton Reagent Overview.