Abstract
One-dimensional (1D) titanate nanotubes (TNTs) have been considered as a novel material for environmental purification due to their novel physical and chemical properties and simple fabrication. One of the potential applications of TNTs is catalytic photodegradation of emerging pollutant. Conventional hydrothermal route is one of the most common methods for fabrication of template-free TNTs. However, the fabrication time is too long, and 24 h is necessary needed. In this study, microwave-assisted hydrothermal method was employed to effectively shorten the reaction time to 3 hr. The 1-D TNTs with areas of 376 m2/g; diameters of about 6.1 nm and lengths of several hundreds nanometers could be easily obtained. In addition, titanate form could be transformed into anatase phase after post heat treatment at 450 °C. Afterward, the as-prepared TNTs were used as a support to deposit Cu2+ ion followed by calcination under NH3/N2 atmosphere for fabrication of Cu-N/TNTs. XRD patterns showed that the crystallization of Cu-N/TNTs was composed of anatase TiO2 and zerovalent copper. The optimal copper loading was found to be at 6 wt%, and the pseudo-first-order rate constants (kobs) for PBA photodegradation by 6 wt% Cu-N/TNT were 0.141 and 0.032 min-1 under UV and visible lights, respectively, which were higher than those of TiO2 P25 by factors of 5.0 and 2.4, respectively. XPS results indicated that N is incorporated into the lattice of Cu-N/TNTs, and the presence of Cu(0) is the main factor to cause the efficient photocatalytic activity under visible illumination. The hetero-junction between metal (Cu0) and semiconductor (TiO2) could effectively suppress the recombination of electron (e-) and hole (h+) pair, resulting in the significant enhancement of the photodegradation efficiency of BPA. However, lower pH condition would cause the increase in copper leaching, followed by the decrease in photocatalytic activity. The photodegradation behavior of BPA followed Langmuir–Hinshelwood kinetics, and the intrinsic rate constant (kr) under UV and visible illumination for photodegradation of BPA were 2.86 and 2.42×10-1 mg/L-min, respectively, which were 3.45 and 1.8 times higher than those of P25. Results obtained in this study clearly demonstrate that TNTs with high surface area can be successfully fabrication within 3 h by microwave-assisted hydrothermal methods. This nanomaterial could serve as a green material for photocatalytic degradation of emerging pollutants. Keyword: titanate nanotubes (TNTs); microwave-assisted hydrothermal method; bisphenol A; photodegradation; Cu-N codoped nanomaterials.