Removal of co-contaminants Cu (II) and nitrate from aqueous solution using kaolin-Fe/Ni nanoparticles

Treatment of wastewater containing co-contaminants poses a significant challenge because heavy metal and inorganic anion contaminants in wastewater have different fates and transport mechanisms. In this paper, bimetallic Fe/Ni nanoparticles supported by kaolinite (K-Fe/Ni) were used to simultaneously remove Cu (II) and nitrate. Results show that the removal of either Cu (II) or nitrate using K-Fe/Ni was mutually affected. Specifically, 42.5% of nitrate was degraded in the presence of 200 mg/L Cu (II), while only 26.9% of nitrate was reduced when Cu (II) was absent. Similar results were also obtained for the removal of Cu (II) in the absence or presence of nitrate. However, the effect of nitrate concentrations on the removal of Cu (II) was less than that for Cu (II) concentrations regarding the degradation of nitrate. To better understand this process, the K-Fe/Ni before and after reacting with Cu (II) and nitrate was characterized with specific surface area, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). These results show that there were the formation of iron oxide, metallic Cu and Ni, after reacting with Cu (II) and nitrate. This indicates that Cu (II) was reduced to Cu onto the surface of K-Fe/Ni, and then a novel catalyst such as K-Fe/Ni/Cu formed. Finally, a possible mechanism for the simultaneous removal of Cu (II) and nitrate is proposed, based on Fe as the reductive agent, whilst both Ni and Cu act as the catalysts for the hydrogen generated from water, and kaolin serves as a support. (C) 2014 Elsevier B.V. All rights reserved.