Photodegradation of unsaturated polyester resin by TiO ₂ and BiFeO ₃ composite photocatalysts under UV and visible‐light irradiation

Photocatalysts based on semiconductor materials have recently been widely used for industrial wastewater treatment. Especially, TiO 2 is known as a widely used photocatalyst thanks to its high photochemical activity, low cost, stability, and non‐toxicity. However, the photochemical activity of TiO 2 is only active in the ultraviolet region. In this study, BiFeO 3 catalyst prepared by the precipitation method exhibited high photocatalytic activity in the visible region, and TiO 2 catalyst prepared by sol–gel method was used in treating unsaturated polyester resin (UPR) condensate water containing very high concentrated persistent organic pollutants including those that create an unpleasant odor. The results showed that the photocatalytic degradation of UPR reached to 43.63% for TiO 2 photocatalysts for a particular dose of photocatalyst (4 g/mL) after 4 h of UV irradiation while that for BiFeO 3 is about 3 times less. Several modern analytical methods such as XRD, SEM, UV–vis DRS, and FT‐IR, have been used. The XRD results showed a stable phase structure and high anatase crystallinity and BiFeO 3 catalyst contains both BiFeO 3 phase and a small amount of Bi 2 Fe 4 O 9 phase. The UV–vis diffuse reflectance spectra of TiO 2 and BiFeO 3 show that BiFeO 3 has a narrow bandgap energy with E g = 2.09 and 1.55 eV corresponding to the visible region. TiO 2 has a band gap energy E g = 3.2 eV corresponding to the UV region.