Interaction between SO₂ and NO in their adsorption and photocatalytic conversion on TiO₂

The simultaneous adsorption and photocatalytic conversion of SO₂ and NO on P25-TiO₂ were studied. In particular, the interaction of SO₂ and NO on each other's adsorption and photocatalytic oxidation was discussed. The adsorption of NO on P25 was negligible when comparing to that of SO₂, while with the coexistence of NO and SO₂ in flue gas, both the adsorption of SO₂ and NO were improved. In the presence of water and oxygen, the photocatalytic oxidation efficiency of NO with an efficiency of >69% was observed on irradiated TiO₂ surface, which lasted for at least 1000 min. Oxygen was found to have much more important effect than water on the photocatalytic oxidation of NO. In the presence of SO₂ however, the photocatalytic process of NO was largely reshaped. The whole process was controlled by the photocatalytic oxidation of SO₂. A dramatic efficiency decease (breakthrough of the catalyst bed) was observed for both NO and SO₂ due to the catalyst deactivation caused by the poisoning of SO₂ oxidation products. Before the breakthrough, the photocatalytic conversion efficiency of NO increased with increasing the SO₂ concentration, which was mainly due to the improved NO adsorption in the presence of SO₂.