Adsorption of Pb2+ from aqueous solution by black TiO2-x nanoparticles with enhanced surface area and porosity

TiO2-x nanoparticles with different colours including white, grey, blue grey, light black and black were synthesized via magnesium (Mg) reduction of white Degussa P25 TiO2 nanoparticles. The as- prepared TiO2-x nanoparticles were used for adsorption of eight metal cations in aqueous solution. Results showed that the TiO2-x nanoparticles with black colour had the best adsorption removal rate for Pb2+. The adsorption kinetic data were fitted with the pseudo-second-order model better than the pseudo-first-order model. The adsorption isotherm was fitted well with both the Langmuir and Freundlich adsorption isotherm. The adsorption capacity of Pb2+ by the black TiO2-x nanoparticles at 15°C, 25°C and 35°C were 36.9, 53.4 and 59.2 mg/g, respectively. It was believed that the high adsorption capacity of the black TiO2-x nanoparticles was mainly due to its large surface area, high pore volume, and unique bimodal pore structures. Finally, it was demonstrated that the as-prepared black TiO2-x could be used for adsorption of Pb2+ from different natural waters such as tap water, lake water and river water.