Expanded Graphite Applied in the Reactive Nano-Fe/Ni Composite as a Support for Reduction of Nitrate in Waters

In addition to the less active metallic nickel, a new strategy was employed to enhance the activity of nano-Fe⁰ for the nitrate reduction. A novel carbon material called expanded graphite was employed to act as the support of bimetallic Ni/Fe. Through a synthesis procedure that includes consecutive steps of an incipient wetness impregnation method, heat treatment, borohydride reduction, a series of Ni/Fe-EG composites with different dosage proportion of Ni/Fe(mass ratio) were synthesized and for the first time were used for treatment of simulated wastewater containing various concentration of nitrate. Compared to the 6%Ni/Fe-EG, 8%Ni/Fe-EG, 12%Ni/Fe-EG and the reported nano-Fe before, the efficiency and rate of nitrate removal using 10%Ni/Fe-EG were significantly promoted without pH control. The 10%Ni/Fe-EG made the initial 60mg-N/L of nitrate mass decrease by 98.4% within only 15min at a rate of 0.23min^-1 where the adsorption of EG was negligible. In addition, the synthesized composites have higher stability in the air and the preparation process need not to be operated in an inert atmosphere at the present (approximately<;50g) experimental scale. Moreover the introduction of EG as support material was benefit to the recovery of metals especially the noble metals.