Effects of phosphoric acid modification of NaZSM-5 zeolite on the properties of TiO_2/ZSM-5 photocatalyst

TiO2/HZSM-5 was synthesized by a sol-gel method using the supporter of HZSM-5 modified by different concentration of phosphoric acid.The photocatalysts were characterized by XRD,SEM,BET,FT-IR and XPS measurements.The results showed that phosphoric acid modification did not change crystalline structure of ZSM-g zeolite and had minor effect on the surface morphology.TiO2 was coated on the surface of the zeolite as TiO2 where titanium existed in its Ti4+ oxidation state.There was no direct chemical bonding between TiO2 and the zeolite.Surface area of the supported photocatalyst increased drastically with increasing phosphoric acid concentration.Degradation rate of reactive brilliant red X-3B varied with phosphoric acid concentration,leading to the optimal concentration of 0.5mol/L.50%TiO2/0.5HZSM-5 showed much higher photocatalytic activity than TiO2,resulting in 93.4% degradation of the dye after 2 h of irradiation,compared with 61.0% degradation on TiO2.