Adsorption behavior of Cu(II) onto titanate nanofibers prepared by alkali treatment

Novel low-cost adsorbents of titanate nanofibers with formula NaxH2-xTi3O7 center dot nH(2)O have been prepared by alkali treatment for Cu(II) removal from aqueous solutions. The nanofibers have structures in which three edge-shared TiO6 octahedras join at the corners to form stepped, zigzag Ti3O72- layers. The sodium cations located between the layers are exchangeable. The results of batch adsorption experiments suggest that the nanofibers with high sodium content can be effective adsorbents for Cu(II) removal. Effects of several important factors such as Na amount in adsorbents, pH, temperature, contact time and initial concentration are systematically studied. Results show that the adsorption is highly pH-dependent and the removal is almost complete (99.8%) for initial concentration under 100 mg/l at pH 4. Equilibrium adsorption follows Langmuir isotherms well and the maximum Cu(II) uptake calculated is 167.224 mg/g. The adsorption kinetics can be explained by pseudo-second-order model well and the time needed for equilibrium is 180 min. Thermodynamic study indicates that the adsorption is spontaneous and endothermic. Desorption of Cu(II) from adsorbents using EDTA-2Na solutions exhibits a high efficiency and the adsorbents can be used repeatedly. These results demonstrate that the titanate nanofibers are readily prepared, enabling promising applications for the removal of Cu(II) from aqueous solutions. (C) 2011 Elsevier B.V. All rights reserved.