Replacing dichromate with hydrogen peroxide in the chemical oxygen demand (COD) test

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Green Chemistry

Background:

• Standard chemical oxygen demand (COD) methods utilize hazardous chromium reagents.
• The conventional COD test requires a significant energy input due to its two-hour heating requirement.
• There is a need for more sustainable and safer analytical methods in environmental monitoring.

Purpose of the Study:

• To propose and validate hydrogen peroxide (H2O2) as a replacement oxidizer for chromium in COD analysis.
• To evaluate the feasibility of a modified COD method operating under milder conditions.
• To assess the energy-saving potential of the proposed H2O2-based COD determination.

Main Methods:

• Development of a proof-of-concept modified COD method using H2O2 as the primary oxidizer.
• Testing the modified method across a concentration range of 10-800 mgCOD/L.
• Comparison of results with the standard chromium-based COD method and a commercial Hach® kit.

Main Results:

• The H2O2-based method demonstrated comparable accuracy to the standard method and a commercial kit.
• The modified procedure significantly reduces reliance on hazardous chromium species.
• Milder reaction conditions were achieved, leading to a decrease in overall energy expenditure.

Conclusions:

• Hydrogen peroxide is a viable and safer alternative oxidizer for COD determination.
• The proposed modification offers a more sustainable and energy-efficient approach to COD analysis.
• This greener method aligns with the principles of sustainable analytical chemistry.