Journal of Zhejiang University SCIENCE
(ISSN 1009-3095, Monthly)

2005   Vol. 6B   No. 3   p.182-186

Reductive denitrification of nitrate by scrap iron filings

HAO Zhi-wei^*, XU Xin-hua, WANG Da-hui

(Department of Environmental Engineering, Zhejiang University, Hangzhou 310027, China)
^*E-mail: hawk200044@126.com
Received May 18, 2004; revision accepted June 7, 2004

Abstract: Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial concentration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe⁰ is discussed.

Key words: Denitrification, Scrap iron filings (SIF), Zero-valent iron, Nitrate, Mechanism
doi:10.1631/jzus.2005.B0182             CLC number: O613.61; X523