Comparative study of photocatalytic and non-photocatalytic reduction of nitrates in water

A Pd-Cu/TiO2 catalyst was comparatively studied in the catalytic and phototocatalytic reduction of nitrates in water. The reaction was systematically investigated in the presence of H-2, HCOOH (which can act as reductant in catalytic experiments and/or hole scavenger in photocatalytic experiments) or mixtures of both, and in the presence or absence of UV irradiation. The catalytic reduction of nitrates was efficiently performed with H-2 or H-2 + HCOOH as the reductant, but was poorly efficient in the presence of HCOOH alone. In the photocatalytic experiments, UV irradiation significantly improved the reaction provided that both H-2 + HCOOH were present. Ammonium formation occurred at high conversion of nitrates, whatever the reaction conditions applied. The combination of UV with formic acid showed the slowest activity but prevented ammonium formation. (C) 2009 Elsevier B.V. All rights reserved.