Photocatalytic reduction of nitrate in seawater using C/TiO2 nanoparticles

• C/TiO2 nanoparticles were synthesized via a sol-gel method.
• Solar photocatalytic removal of nitrate from seawater was investigated using C/TiO2..
• Carbon modification enhanced the photocatalytic activity of C/TiO2.
• The highest removal rate was obtained at pH 3 and catalyst dose of 0.5 g L−1.
• Photocatalytic removal data were successfully expressed by the pseudo first-order reaction kinetics.

This study investigates the photocatalytic reduction of nitrate in seawater using carbon-modified titanium oxide (C/TiO2) 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 (TiO2) and reference TiO2 P25 photocatalysts were used for comparison. The elemental composition determined through energy dispersive spectroscopy (EDS) analysis evidenced the carbon modification for C/TiO2 nanoparticles. The optical bandgap energy for C/TiO2 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/TiO2 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.

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