Selective reduction of nitrate to nitrogen by Fe 0 -Cu 0 -CuFe 2 O 4 composite coupled with carbon dioxide anion radical under UV irradiation

Zero-valent iron (Fe ) 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 (NO ) to nitrogen gas (N ) with high efficiency and N selectivity was investigated using Fe-based material (Fe -Cu -CuFe O ) combined with citric acid (CA) and ultraviolet (UV) irradiation. In this strategy, the nitrate was firstly reduced to nitrite (NO ) by Fe -Cu -CuFe O /UV process, and then the produced NO could be further reduced to N by carbon dioxide anion radicals (CO ) which was generated from CA that was added later. In this process, the selective reduction of NO to NO was a key step. For this purpose, we synthesized Fe -Cu -CuFe O 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 CuFe O . The selective reduction of NO to NO in Fe -Cu -CuFe O /UV process was due to that the Cu was the electron enrichment center and the photo-generated hole could suppress the NO reduction to NH by Fe . In this proposed strategy, 100% NO removal efficiency and 96.3% N selectivity were achieved when the initial NO concentration was 30 mg N/L and the reduction time was 60 min. The denitrification mechanism of the Fe -Cu -CuFe O /UV/CA system was proposed.