Advanced removal of toluene in aerosol by adsorption and photocatalytic degradation of silver-doped TiO2/PU under visible light irradiation

Abstract

We synthesized a novel Ag–TiO₂/PU material for the effective removal of gaseous toluene by both adsorption and photocatalytic degradation. The Ag particles, which were distributed on the TiO₂ surface, and the Ag dopants, which were incorporated into the TiO₂ lattice, increased the electron–hole pair separation efficiency of TiO₂. Therefore, Ag–TiO₂/PU exhibited high photocatalytic degradation of toluene even under visible light. Porous polyurethane (PU) was used to immobilize the enhanced TiO₂, to increase the adsorption capacity of the photocatalyst. The synthesized Ag–TiO₂/PU removed gaseous toluene even under dark conditions via adsorption. The removal of gaseous toluene by Ag–TiO₂/PU under visible light conditions was due to the combination of both adsorption and photocatalytic degradation. The oxygen content in the gas stream insignificantly affected the toluene adsorption by the Ag–TiO₂/PU. However, the photocatalytic degradation of toluene by Ag–TiO₂/PU increased with increasing oxygen content and stabilized when the oxygen content exceeded 15%. These results suggest that ambient air can be used economically as an oxygen source for the photocatalytic degradation of gaseous toluene by Ag–TiO₂/PU under visible light conditions. Under visible light irradiation, 6% Ag–TiO₂/PU, which was the Ag/TiO₂ ratio that optimized the photocatalytic degradation activity of TiO₂, removed 85.2% of the toluene in 100 ppm inlet gas, of which 90.3% was mineralized into CO₂ and H₂O.