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

Abstract

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⁺.