Enhanced photoactivity of Cu-deposited titanate nanotubes for removal of bisphenol A

Abstract

One-dimensional nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the Cu-deposited titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method at 150 degrees C and then 0.5-2 wt% Cu(II) ions were photodeposited onto the calcined TNTs at 500 degrees C for enhanced photodegradation of bisphenol A (BPA) under illumination of 365 nm UV light. The as-synthesized TNTs showed tubular structures with the outer diameter and inter-layer spacing of 7-10 and 0.8 nm, respectively. The X-ray absorption near-edge spectral results provided a strong support on the partially structural change from layered trititanate to anatase TiO2 through the distortion of octahedral TiO6 unit at 500 degrees C and the production of mixture of CuO and Cu2O after photodeposition of Cu ions, resulting in the formation of Cu-deposited TiO2/TNT nanocomposites to enhance the photocatalytic activity. A nearly complete removal of BPA by the Cu-deposited TiO2/TNTs was observed, and the pseudo-first-order rate constants (k(obs)) for BPA photodegradation by Cu-deposited TiO2/TNTs at pH 7.0 were 1.8-5.2 and 4.3-12.7 times higher than those of pure Degussa P25 and ST01 TiO2, respectively. In addition, the k(obs) for BPA photodegradation reached the maximum value of 0.253 +/- 0.032 min(-1) at 1 wt% Cu(II). The X-ray photoelectron spectra showed that the ratio of Cu2O to total Cu increased from 3.2% in the dark to 35.2% after illumination of 365 nm UV light for 5 min. In addition, electron paramagnetic resonance results indicated that the copper ions could serve as the electron mediators to prolong the retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by Cu-deposited TiO2/TNTs. (C) 2012 Elsevier B.V. All rights reserved.