Arsenate adsorption onto Fe-TNTs prepared by a novel water-ethanol hydrothermal method: mechanism and synergistic effect.

Arsenate adsorption onto Fe2O3 was highly restricted at acidic condition due to dramatic dissolution. To overcome this difficulty, iron oxide nanoparticle-grafted titanate nanotubes (Fe-TNTs) were synthesized by a facile one-step water-ethanol hydrothermal method and used to remove As(V) from aqueous solutions. This new adsorbent was acid-resistant, and showed a large As(V) adsorption capacity of 90.96 mg/g determined by two-site Langmuir model, which was almost 3 times of the original TNTs. Fe2O3 was proved to bonded to the surface of TNTs by TEM and XRD analysis and synergy of Fe2O3 and TNTs was of great help to excellent As(V) adsorption. Load of Fe2O3 greatly enhanced the point of zero charge. Moreover, tubular TNTs not only inhibited dissolution of Fe2O3 at low pH, but also maintained good sedimentation property. The hydroxyl groups on Fe-TNTs surface played the most important role in As(V) adsorption. Electrostatic interaction followed by complexation was confirmed to be the primary adsorption mechanism by means of XPS analysis. Desorption capability and reuse performance of Fe-TNTs were also investigated, and satisfactory As(V) adsorption was further found with NaOH desorbed even after three reuse cycles.