Self-assembled flower-like TiO2 on exfoliated graphite oxide for heavy metal removal

We describe that a hydrothermal preparation of flower-like TiO2-graphene oxide (GO-TiO2) hybrid by stirring a titanium oxide precursor in isopropyl alcohol with GO colloidal solution. The GO-TiO2 hybrid was applied for the removal of heavy metal ions from water. The oxygenated functional groups of exfoliated graphite oxide showed a high removal capacity of heavy metals. The flower-like TiO2 on GO structure significantly improved the removal efficiency of heavy metals. For example, the GO-TiO2 hybrid adsorption capacities of heavy metal ions, after 6 h and 12 h of hydrothermal treatment at 100 °C, were respectively 44.8 ± 3.4 and 88.9 ± 3.3 mg/g for removing Zn2+, 65.1 ± 4.4 and 72.8 ± 1.6 mg/g for removing Cd2+, and 45.0 ± 3.8 and 65.6 ± 2.7 mg/g for removing Pb2+ at pH 5.6. In contrast, colloidal GO under identical condition showed removal capacities of 30.1 ± 2.5 (Zn2+), 14.9 ± 1.5 (Cd2+), and 35.6 ± 1.3 mg/g (Pb2+). TiO2 blossoms markedly formed upon GO as the hydrothermal treatment time at 100 °C increased from 6 h to 12 h. Longer treatment times resulted in an increase in the surface area of GO-TiO2 hybrid and thus its removal capacity of heavy metal increased.