Adsorption behavior of Zr(IV) and Hf(IV) on a silica-based macroporous TODGA adsorbent

In order to separate Zr(IV) and Hf(IV) in acidic solution,several kinds of silica-based macroporous adsorbents were synthesized.Their adsorption selectivity for Zr(IV) and Hf(IV) in HCl solution was investigated,and the TODGA adsorbent for the two elements had the largest adsorption difference.The effects of acid type,HCl concentration,and temperature on the adsorption behavior of Zr(IV) and Hf(IV) onto the TODGA adsorbent were conducted by batch experiments.It was found that H+exhibited a quite strong influence on adsorption capacity of Zr(IV) and Hf(IV).Isotherm fitting showed that the Langmuir model agrees well with the experimental data.The thermodynamic parameters indicate that the adsorption processes for both elements are endothermic reactions.The TODGA adsorbent had the higher adsorption selectivity for Zr(IV) over Hf(IV) and could be promising for their mutual separation.