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