Copper-incorporated titania nanotubes for effective lead ion removal

Small copper (Cu2+) dopant levels were successfully diffused into titanium dioxide (titania or TiO2) nanotube lattice via an incipient wet impregnation technique. This study investigated the optimum Cu2+ dopant content to be incorporated into the TiO2 nanotubes to achieve an effective lead ion (Pb(II)) removal system. The exciton states of the PL intensities varied in the following order: pure TiO2>0.6 M Cu–TiO2>0.1 M Cu–TiO2>0.06 M Cu–TiO2>0.01 M Cu–TiO2. The significant quenching of the PL intensity indicates that incorporation of the appropriate amount of Cu2+ dopants into the TiO2 lattice markedly enhanced the charge-carrier separation and transport. The photocatalytic ability of the samples was evaluated by the removal of the Pb(II) ions under UV illumination. The results show that the Cu dopants in the TiO2 lattice at the optimum concentration (0.8 at%) acted as photoinduced electron mediators and thus increased the Pb(II) ion removal efficiency. The maximum Pb(II) ion removal rates for the 0.01 M Cu–TiO2 nanotubes and after five hours of UV illumination were approximately 56.3% and 79.5% at pH 5 and pH 11, respectively. The generation of strong oxidizing agents (OH radicals) effectively reduces the toxic Pb(II) ions into PbO/PbOH.