Selective reduction of nitrate to nitrogen by Fe0-Cu0-CuFe2O4 composite coupled with carbon dioxide anion radical under UV irradiation.

Journal: Chemosphere
Published:
Abstract

Zero-valent iron (Fe0) has been widely used for the reduction of nitrate, but the end reduction product is mainly ammonium. Here, a novel strategy for selective reduction of nitrate (NO3-) to nitrogen gas (N2) with high efficiency and N2 selectivity was investigated using Fe-based material (Fe0-Cu0-CuFe2O4) combined with citric acid (CA) and ultraviolet (UV) irradiation. In this strategy, the nitrate was firstly reduced to nitrite (NO2-) by Fe0-Cu0-CuFe2O4/UV process, and then the produced NO2- could be further reduced to N2 by carbon dioxide anion radicals (CO2•-) which was generated from CA that was added later. In this process, the selective reduction of NO3- to NO2- was a key step. For this purpose, we synthesized Fe0-Cu0-CuFe2O4 composite by simple chemical replacement and in-situ growth process, which made it have a delicate structure with good contact between Cu and Fe and CuFe2O4. The selective reduction of NO3- to NO2- in Fe0-Cu0-CuFe2O4/UV process was due to that the Cu0 was the electron enrichment center and the photo-generated hole could suppress the NO3- reduction to NH4+ by Fe2+. In this proposed strategy, 100% NO3- removal efficiency and 96.3% N2 selectivity were achieved when the initial NO3- concentration was 30 mg N/L and the reduction time was 60 min. The denitrification mechanism of the Fe0-Cu0-CuFe2O4/UV/CA system was proposed.

Authors
Jinrui Guo, Jinhua Deng, Baohua An, Jing Tian, Junshu Wu, Yong Liu