Degradation of metronidazole by nanoscale zero-valent metal prepared from steel pickling waste liquor

In this study, steel pickling waste liquor was employed to obtain reactive nanoscale zero-valent metal (nZVM) with the purpose of engineering application. The degradation of metronidazole reacted with as-prepared nZVM in water was investigated to explore the feasibility of using the nZVM to treat antibiotics in wastewater. The synthesized nZVM was characterized by Brunauer-Emmett-Teller (BET) surface analyzer, transmission electron microscopy (TEM), scanning electron microscopy (SEM). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectrometer (EDS). The results showed that the nZVM (20-40 nm) with crystalline structure had a BET surface area of 35 m(2)/g. XPS and EDS only detected Fe, C and O on the surface, suggesting Ni and Zn distributed inside the core of nanoscale alloy. Degradation of metronidazole followed the pseudo-first-order kinetics, and the observed reaction rate constant (k(obs)) could be improved with increasing nZVM dosage, as well as with diminishing initial metronidazole concentration and pH. A high reaction rate was observed at reduction potential, indicating that electrons and hydrogen species produced by nZVM were driving forces of reaction. The surface area-normalized rate coefficient (k(SA)) for nZVM (0.254 L min(-1) m(-2)) was 375.2 times larger than that for commercial iron powder (6.67 x 10(-4) L min(-1) m(-2)). Several possible pathways of degradation of metronidazole were proposed according to the results of UV-vis spectra and HPLC chromatograms. (C) 2010 Elsevier B.V. All rights reserved.