Reduction of Nitrate in Groundwater with Modified Iron Nanoparticles

Nitrate reduction using laboratory synthesized Fe/Ni bimetallic nanoparticles was discussed. Nanoparticles were characterized by TEM-EDS, SEM, XRD and BET techniques. Denitriflcation of 80 mg-N/L nitrate solutions was performed with various Ni contents (1.0, 5.0, 10 and 20%) nanosized Fe/Ni particles compared with monometallic nano-scale FeO. The introduction of Ni enhances the reduction rate remarkably and 5.0% Ni loading shows the highest reactivity, for which nitrate was removed completely in 40 min when iron concentration was 1.5 g/L. Different from iron powder, Fe/Ni nanoparticles behaved the largest reaction rate under the condition of neutral solution pH without pH control. After slowly ageing 22 h, the reactivity of freshly prepared nanoscale Fe/Ni particles decreased about 10 times, but with the followed 44 h ageing, little decreasing of reactivity was observed which is equivalent to freshly synthesized nano-FeO. The effects of initial nitrate concentration and the reduction kinetics were also investigated. For Fe/Ni bimetallic nanoparticles, about 90% nitrate was transformed to ammonium, and nitrite was detected as intermediate product.