Removal of hexavalent chromium from wastewater by Cu/Fe bimetallic nanoparticles

Abstract BackgroundNanoscale zerovalent iron (nZVI) is a promising material for removing heavy metals from wastewater. However, passivation of nZVI hinders its efficiency in water treatment. Loading another catalytic metal has been found to improve the efficiency significantly. In this study, Cu/Fe bimetallic nanoparticles were prepared by liquid-phase chemical reduction for removal of hexavalent chromium (Cr(VI)) from wastewater. Purpose of this study was to clarify the effects and mechanisms of Cu loading on the removal efficiency of Cr(VI).ResultsThe results showed that Cu loading can significantly enhance the removal efficiency of Cr(VI) by 29.3% to 84.0%, and the optimal Cu loading rate was 3% (wt%). The removal efficiency decreased with increasing initial pH and Cr(VI) concentration. It was found that Cr(VI) removal followed a pseudo-first-order kinetic model. When the Cu loading rate was 3%, the initial concentration of Cr(VI) was 100 mg/L, the observed first-order rate coefficient (kobs) was 0.016 min-1 for Cu/Fe bimetallic nanoparticles at pH of 3.5, which was twice than that of nZVI (0.008 min-1). X-ray photoelectron spectroscopy (XPS) analysis indicated that Cr(VI) was completely reduced to Cr(Ⅲ) and precipitated on the particle surface as hydroxylated Cr(OH)3 and CrxFe1-x(OH)3 coprecipitation.ConclusionsIn this study, it was found that the loading of Cu can significantly increase the specific surface area and the Cr(VI) remove efficiency of nZVI, and the removal efficiency decreases with increasing pH and Cr(VI) initial concentration. Therefore, Cu loading can alleviate the passivation of nZVI effectively and can be beneficial for the application of iron-based nanomaterials in remediation of wastewater.