Chemical Reduction of Nitrate in Aqueous Solution by Iron Powder

Abstract:

Nitrate is a common groundwater contaminant and poses health and environmental threats. Reductive denitrification of nitrate by zero-valent iron was investigated in unbuffered solutions at 20 °C. Nitrate was effectively removed at low initial solution pH. The reaction was accompanied by the production and then disappearance of a small quantity of nitrite, suggesting that nitrite was the intermediate and subsequently further reduced. A rapid rise in solution pH was also observed during the reaction. At the initial pH of 4, a reduction of 90% in nitrate concentration from 60 to 7.0 mg/L at 60 min was observed. The extent of nitrate removal decreased with increasing solution pH within the tested range of 3 - 6, suggesting that the reaction was an acid-driven process. The extent of nitrate removal also increased with Fe dosage over the range of 5 - 20 g/L, as higher Fe dosages provided more reactive surfaces. It is proposed that protons participate in the nitrate reduction by Fe₀ via an initial reduction of protons to reduced hydrogen species followed by a subsequent reaction with nitrate. The hydrolysis of Fe corrosion products (e.g., ferrous ions) produces protons, in particular, near the surfaces of Fe, which drives the reaction to continue.

• Periodical: Advanced Materials Research (Volume 777)
• Pages: 71-76
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.777.71
• Online since: September 2013
• Authors: Hong Yi Zhou, Si Liang, Si Si Zeng, Shuang Jian Lei
• Keywords: Chemical Reduction, Mechanism, Nitrate, pH Effect, Zero-Valent Iron

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