Simultaneous removal of nitrate and microbial pollution from water by the electro-catalytic activity of iron and magnetic nanoparticles supported on nickel foam

This study aimed to provide an effective electro-catalytic system for the simultaneous reduction of nitrate and disinfection of contaminated water by the electro-catalytic performance of Ni-Fe/Fe3O4 cathode.

At first, the Ni-Fe electrode was synthesized by the electro-deposition process. Then its physical properties were analyzed by scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and photoelectron X-ray spectroscopy (XPS). Simultaneous disinfection and reduction of nitrate were performed under the following conditions: 15 mg Fe3O4 nanoparticles, pH 6.5, NaCl 10 mM, 50 mg/L nitrate, 105 CFU/mL and current density 4 mA/cm2.

According to the results obtained in the absence of nitrate, 100 % of Escherichia coli bacteria were disinfected after 12 minutes. In the presence of nitrate, the time of complete disinfection increased to 120 minutes. In the absence of bacteria, 83% of nitrate was removed in 240 minutes, and in the presence of bacteria, the nitrate reduction efficiency increased slightly to 88%. In the nitrate reduction process, nitrite (0.22 mg/L) and ammonium (3.6 mg/L) were produced. In the presence of bacteria, the amounts of nitrite and ammonium produced increased to 0.42 mg/L and 7.3 mg/L.

The results show the outstanding ability of Ni-Fe/Fe3O4 electrode in electro-catalytic reduction of nitrate and disinfection of contaminated water separately and simultaneously with high efficiency and high selectivity to nitrogen.