Photocatalytic degradation of SO2 using TiO2-containing silicate as a building coating material

Effects of TiO2 content in silicate coatings on resultant photocatalytic-degradation of SO2 were experimentally investigated. An in-house designed reaction system with simulated solar irradiation was employed to examine the degradation of SO2 (14 ppm) in batch. Various processes involved in the photocatalytic degradation of SO2 were systematically characterized, including photolysis of SO2, sorption of SO2 onto the coating surface, as well as photocatalytic degradation of SO2 by the silicate coating containing 5% or 15% TiO2 (of silicate solid weight). Each experiment provides the temporal concentration trend in SO2 for a duration of 120 min and is repeated for 10 rounds. Results show that photolysis reduces around 10% SO2. Physi- and chemi-sorption together is responsible for about 30% reduction in SO2. Photocatalytic oxidation alone removes up to around 40% of SO2 concentration. The temporal trend of SO2 degradation remains consistent among the 10 repeated reaction cycles regardless of the content of TiO2 in the silicate coating. A total of 71–86% of SO2 concentration is removed by the silicate coating containing 15% TiO2 following a trend of pseudo-first-order reaction kinetics. The overall removal of SO2 by the silicate coating containing 15% TiO2 is twice as efficient as that containing 5% TiO2.