Photocatalytic reduction of nitrate in seawater using C/TiO2 nanoparticles

Abstract This study investigates the photocatalytic reduction of nitrate in seawater using carbon-modified titanium oxide (C/TiO 2 ) nanoparticles under different reaction conditions. Formic acid was used as a sacrificial electron donor for inhibiting the mechanism of electron/hole recombination on the photocatalyst. Unmodified titanium oxide (TiO 2 ) and reference TiO 2 P25 photocatalysts were used for comparison. The elemental composition determined through energy dispersive spectroscopy (EDS) analysis evidenced the carbon modification for C/TiO 2 nanoparticles. The optical bandgap energy for C/TiO 2 has been remarkably reduced to 1.78 eV which in turn enhanced its performance towards the photocatalytic removal of nitrate under ultraviolet as well as natural sunlight irradiation. Factors including C/TiO 2 loading, initial nitrate concentration, solution pH and hole scavenger concentration were studied to attain the optimal reaction conditions. The highest nitrate photocatalytic removal rate was obtained at catalyst loading of 0.5 g L −1 , pH 3 and 0.04 M of formic acid. The kinetic study showed that the photocatalytic nitrate removal from seawater using carbon-modified titanium oxide was successfully expressed by the pseudo first-order reaction kinetics.