Coupled removal of bisphenol A and copper ion by titanate nanotubes fabricated at different calcination temperatures

One-dimensional (1-D) nanotubes are promising nanostructured materials for a wide variety of environmental applications. In this study, the 1-D titanate nanotubes (TNTs) were fabricated using an alkaline hydrothermal method and then calcined at various temperatures ranging from 200 to 600 °C in air for 4 h for coupled removal of bisphenol A (BPA) and Cu(II) ion. The as-synthesized TNTs showed tubular structures with diameter of 8–10 nm and length of few μm. After calcination at 400–600 °C, the well-crystallized anatase TiO2 nanoparticles were produced on the tube walls to form titania/TNT nanocomposites, resulting in the decrease in specific surface area and the increase in isoelectric point. The as-synthesized and calcined TNTs have good Cu(II) adsorption capacity, and the maximum Langmuir adsorption capabilities decreased from 160 mg/g for as-synthesized TNTs to 35 mg/g for TNT-600, presumably due to the decrease in specific surface area. In addition, the calcined TNT showed a good photocatalytic activity towards BPA degradation when compared with the as-synthesized TNTs. The coexistence of Cu(II) ion and BPA exhibited the synergistic effect on the enhancement of photocatalytic activity of calcined TNTs. Electron spin resonance results indicated that the copper ion was first adsorbed onto the negatively charged TNTs, and then served as the electron trap to prolong to retention time of photo-generated radicals, resulting in the enhancement of photodegradation efficiency and rate of BPA by calcined TNTs.

► The titanate nanotubes (TNTs) with diameter of 8–10 nm were successfully fabricated.
► The calcination of TNT at temperature >400 °C would form TiO2/TNT nanocomposite.
► The Cu(II) adsorption capacity by TNTs decreased upon increasing calcination temperature.
► The coexistence of Cu(II) enhanced the photoactivity of TNTs towards BPA degradation.
► ESR showed that the Cu(II) prolongs the retention time of photogenerated radicals.