Nitrate reduction in water by aluminum–iron alloy particles catalyzed by copper

• Al–Fe alloy is superior to aluminum and iron for nitrate reduction from water.
• Nitrate reduction by Al–Fe alloy is significantly enhanced by copper chloride.
• An intermetallic alloy compound plays an important role in nitrate reduction.

Nitrate contamination is increasingly becoming a global health and environmental issue, because nitrate concentration in ground and surface waters has exceeded the safe limit in many places of the world. Removal of such low levels of nitrate from water by conventional processes in an efficient and cost-effective manner poses a significant challenge in water treatment industry. Chemical reduction using zero-valent iron and aluminum particles for nitrate removal from water has been extensively investigated. In this study, aluminum–iron alloy particles (containing 10% iron) were investigated for removal of nitrate from water and compared with zero-valent aluminum, iron and mixtures of aluminum and iron particles. The aluminum–iron alloy and metallic aluminum particles were inactive for nitrate reduction due to the presence of ubiquitous aluminum oxide layer on surface of the particles. Nitrate reduction was significantly promoted by copper chloride and the alloy particles showed the fastest rate and largest efficiency of the reduction. The significant promotion of the reduction was likely due to the catalytic effect of copper and an intermetallic alloy compound Al13Fe4. The catalytic mechanism of nitrate reduction by the alloy material was analyzed and the reduction pathway was identified as nitrite and ammonium to be intermediate and end product, respectively.

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