Synthesis and characterization of a phosphorus-doped TiO2 immobilized bed for the photodegradation of bisphenol A under UV and sunlight irradiation

Abstract

The surface of Degussa P25 TiO2 was modified by post-treatment with phosphoric acid to form phosphorus-doped TiO2 (P-TiO2). The surface properties of P-TiO2 were analyzed using X-ray diffraction, ultraviolet (UV)–Vis spectrophotometry, scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of TiO2 and P-TiO2 for the degradation of bisphenol A (BPA) under UV and sunlight irradiation was determined. The band gap of TiO2 and P-TiO2 was 3.1 and 3.0 eV, respectively. The FTIR and XPS results indicate that the phosphorus does not exist only on the surface of TiO2, but likely in a Ti–O–P bond. After reaction for 67 min, BPA degradation by the UV/TiO2, UV/P-TiO2, sunlight/TiO2 and sunlight/P-TiO2 systems was 59, 65, 84 and 92 %. The BPA degradation rate obeyed pseudo-first order kinetics; moreover, the rate constant of UV/TiO2, UV/P-TiO2, sunlight/TiO2 and sunlight/P-TiO2 was 0.792, 0.942, 1.788, and 2.208 h−1. The degradation of BPA by the photocatalytically enhanced P-TiO2 was due to the narrowed band gap, increased number of hydroxyl groups on surfaces, and the decreased recombination rate of photogenerated electrons and holes in P-TiO2. The cyclic utility of P-TiO2 remained high. This study suggests that sunlight/P-TiO2 is a novel system for the rapid degradation of BPA.