Removal of heavy metal lead(II) using nanoscale zero-valent iron with different preservation methods

Abstract

In this study, different nanoscale zero-valent irons (nZVI) were prepared in order to improve their stability and reactivity to heavy metal lead (Pb (II)). The composition, particle size and morphology of obtained nZVI were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM). The effects of nZVI dosage, pH, initial Pb (II) concentration and reaction time on the removal efficacy of Pb (II) were investigated. The results show that undried nZVI has more active sites due to its weaker oxidation, and thus the removal efficiency of Pb(II) by undried nZVI was higher than that by dried nZVI. As a result, the same removal efficiency could be achieved with the use of less undried nZVI for the identical concentration of Pb(II). Furthermore, the experimental procedure could be apparently simplified, which eliminates the steps of washing, separation and dehydration compared with the traditional preparation method. The experimental data could be well fitted by the Langmuir adsorption isotherm model, and the maximum adsorption capacity of dried and undried nZVI is 671.14 and 807.23 mg·g−1 at pH 6, respectively. The experimental data followed the pseudo second-order kinetic model with a kinetic constant of 7.65 × 10−4 and 1.39 × 10−3 for undried and dried nZVI, respectively. In conclusion, undried nZVI had high adsorption capacity and adsorption rate for Pb(II) in the solution.