Zero-valent iron reduction of nitrate in the presence of ultraviolet light, organic matter and hydrogen peroxide

Abstract

This paper describes the use of metallic iron (Fe 0) powder for nitrate removal in a well-mixed batch reactor. Important variables explored include Fe 0 dosage (1–3 g/L), UV light intensity (64–128 W), and the presence of propanol (20 mg/L as DOC) and H 2O 2 (100–200 mg/L). Accumulation of ferrous ions released from the Fe 0 surface can be expressed by an S-curve, which involves lag growth phase, exponential phase, rate-declining phase, and saturation phase. The removal of nitrate increases with increasing Fe 0 dosage; however, the removal makes no difference as the Fe 0 dosage is greater than 2 g/L. UV irradiation retards the dissolution of ferrous ion and the removal of nitrate. The species of propanol, which has a functional group of –OH, plays a role of organic inhibitor for Fe 0 corrosion. The presence of H 2O 2 appears to inactivate all reactions as the Fe 0 of 10 μm was used; the final H 2O 2 remains intact throughout the entire reaction period, and there were no removal of nitrate and no dissolution of ferrous ion. Surprisingly, with the use of a larger Fe 0 particle size of 150 μm, the H 2O 2 was seen to decompose rapidly through Fenton reaction. Nevertheless, the rate of ferrous accumulation or nitrate removal is slow.