Pb(II) adsorption capacity and behavior of titanate nanotubes made by microwave hydrothermal method

Presence of heavy metals in water bodies is of great concern. Adsorption removal is a proven technology, but search for adsorbents with high adsorption capacities is still in great need.Titanate nanotubes (TNTs) made by the microwave hydrothermal method possess large surface areas and high sodium contents which make them good candidates for removal of heavy metals from aqueous solutions. TNT samples made from three different microwave intensities (40-W, 400-W, and 700-W) and energies were evaluated for their adsorption capacities of Pb(II) ions. Adsorption kinetics and equilibrium studies were conducted under various solution pH, coupled with XPS, Raman, and DRIFT spectroscopies and zeta potential measurements.The findings of this study include (1) these TNT samples are great adsorbents for Pb(II) removal, and the adsorption capacity can be as high as 2000 mg Pb(II)/g TNT even under acidic pH conditions; (2) exchange with sodium ions and binding with oxygen atoms on the TNT surfaces account for most of Pb(II) removal from the aqueous phase; and (3) adsorption capacities of TNT samples did not increase linearly with microwave intensities and energies used in hydrothermal treatment.