Reductive denitrification using zero-valent iron and bimetallic iron.

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies

Background:

• Nitrate contamination in water poses environmental and health risks.
• Reductive denitrification is a key process for nitrate removal.
• Optimizing reaction conditions and materials is crucial for efficient nitrate reduction.

Purpose of the Study:

• To investigate the reductive denitrification of nitrate using microscale zero-valent iron (ZVI) and palladium-coated iron (Pd/Fe).
• To evaluate the effect of variable pH on nitrate reduction rates and kinetics.
• To assess the impact of palladium coating on nitrogen selectivity and engineering applicability.

Main Methods:

• Controlled experiments using microscale zero-valent iron (ZVI) and palladium-coated iron (Pd/Fe).
• Variable pH conditions maintained using an auto-controlling system.
• Kinetic analysis of nitrate reduction under different pH and concentration regimes.

Main Results:

• Higher nitrate reduction rates were observed at lower pH.
• Pseudo-first-order kinetics dominated at lower pH, shifting towards zero-order at higher pH and nitrate concentrations.
• Palladium coating on iron (Pd/Fe) significantly increased nitrogen selectivity.
• Complete conversion of intermediates to ammonia required several hours, impacting direct mass loss calculations.

Conclusions:

• Lower pH favors faster reductive denitrification rates.
• Palladium coating enhances nitrogen selectivity in iron-based denitrification systems.
• The Pd/Fe system demonstrates potential for efficient nitrate removal with combined electron source and catalyst benefits.