Nanoscale zerovalent iron (nZVI) has demonstrated high efficacy for treating nitrate contamination, but the influences of different metals doped on nZVI on nitrate reduction pathway have not been well studied. Our study suggested that ammonium production had a close relationship with the binding energies of N-O, Fe-N, Fe-O, and Fe-H. Cadmium (Cd) addition resulted in a significant enhancement of the reactivity of nZVI with nitrate: while 30% of nitrate was reduced by nZVI within 2 hr in the absence of Cd, complete nitrate reduction was observed in the presence of 40 mg-Cd/L due to the formation of Cd islands (Cd(0) and CdO) on the nZVI particles. Furthermore, while nitrate was reduced mostly to ammonium when Cd(II) was absent or in excess (= 40 mg-Cd/L), up to 20% of the initial nitrate was reduced to nitrite at Cd(II) concentrations < 40 mg/L. The X-ray diffraction analysis indicated that the appearance of Cd(0) was responsible for the nitrite accumulation. For nZVI particles with 1 wt. % Cu, Ag, or Au doping, nZVI with Au reduced nitrite yield to less than 3% of the initial nitrate, which was due to the highly facilitated electron flow and barely no nitrite dissolution into catalyst.

Effect of cadmium on nitrate reduction by nanoscale zerovalent iron (nZVI) and catalysts doped nZVI

248th National Meeting (2014)

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