Ti₂O₃/TiO₂-assisted solar photocatalytic degradation of 4-tert-butylphenol in water

Colored Ti₂O₃ and Ti₂O₃/TiO₂ (mTiO) catalysts were prepared by the thermal treatment method. The effects of treatment temperature on the structure, surface area, morphology and optical properties of the as-prepared samples were investigated by XRD, BET, SEM, TEM, Raman and UV–VIS spectroscopies. Phase transformation from Ti₂ O₃ to TiO₂ rutile and TiO₂ anatase to TiO₂ rutile increased with increasing treatment temperatures. The photocatalytic activities of thermally treated Ti₂ O₃ and mTiO were evaluated in the photodegradation of 4-tert-butylphenol (4-t-BP) under solar light irradiation. mTiO heated at 650^◦ C exhibited the highest photocatalytic activity for the degradation and mineralization of 4-t-BP, being approximately 89.8% and 52.4%, respectively, after 150 min of irradiation. The effects of various water constituents, including anions (CO²⁻ 3^{, NO}3, Cl and HCO⁻3) and humic acid (HA), on the photocatalytic activity of mTiO-650 were evaluated. The results showed that the presence of carbonate and nitrate ions inhibited 4-t-BP photodegradation, while chloride and bicarbonate ions enhanced the photodegradation of 4-t-BP. As for HA, its effect on the degradation of 4-t-BP was dependent on the concentration. A low concentration of HA (1 mg/L) promoted the degradation of 4-t-BP from 89.8% to 92.4% by mTiO-650, but higher concentrations of HA (5 mg/L and 10 mg/L) had a negative effect.