Photocatalytic degradation of 4,4′-biphenol in TiO2 suspension in the presence of cyclodextrins: A trinity integrated mechanism

Abstract Effect of cyclodextrins (CDs) on the photodegradation of 4,4′-biphenol (BIP) in TiO 2 suspension was examined using a 250 W metal halide lamp ( λ  ≥ 365 nm) as irradiation light source. The adsorption of BIP on TiO 2 surface was also investigated in both conditions that CDs is absence or presence, as well as the inclusion complex of CDs with BIP. Results showed that, the behaviors of inclusion complex of BIP with CDs were the predominant factor in the photocatalytic reaction. A larger inclusion constant value (5600 M −1 ) of BIP with β-CD followed by the enhancement of adsorption on TiO 2 surface leads to acceleration of photodegradation, while α-CD showed opposite effect on the photodegradation because of a much smaller inclusion constant (51 and 355 M −1 was obtained for α-CD/BIP and α-CD 2 /BIP, respectively). The reaction constants were 1.35, 1.17 and 2.48 μM min −1 for BIP in the absence of CDs, in the presence of α-CD and in the presence of β-CD, respectively. XRD analysis demonstrated that TiO 2 conserved their anatase crystal features after 5-h irradiation. A trinity interaction model of BIP photodegradation in TiO 2 suspension containing cyclodextrins was also proposed in this work. It would be beneficial to have a depth-in mechanism of CDs effect on reactant's photodegradation in TiO 2 suspension that would probably lead to a high efficiency and selectivity for the photodegradation of pollutants using TiO 2 as catalyst.