Mesoporous titanate-based cation exchanger for efficient removal of metal cations

A mesoporous titanate-based Na+-exchanger with high surface area and tunable pore size has been successfully synthesized by using NaOH-etched silica mesoporous microspheres as templates. Templating against porous silica microspheres followed by etching the templates with base produces amorphous sodium titanate spheres with controllable porosity. The resultant Na+ exchangers have BET surface areas as high as 386.47 m2 g−1 and average pore sizes tunable from ∼5 nm to 30 nm. Adsorption experiments indicate that the as-obtained Na+-exchangers possess excellent adsorption capacity (up to 2.90 mmol g−1) for ten metal cations in low concentration ranges without any selectivity due to fast ion exchange between Na+ and the target cations, while at high concentrations, the selectivity sequence follows the order of Hg2+ < Co2+ < Cd2+ < Cu2+ < Ni2+ < Mn2+ < Zn2+ < Sn4+ < Cr3+ < Fe3+.