Prof. HUANG Qunying's team from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with Prof. NING Shunyan's team from South China University, developed a novel inorganic silica-based adsorbent for the highly selective separation of strontium from acidic medium.

The results were published in Journal of Environmental Chemical Engineering.

Radioactive strontium (⁹⁰Sr) is considered to be one of the most dangerous radionuclides due to its high biochemical toxicity. During the vitrification process of high-level liquid waste, the presence of ⁹⁰Sr can cause instability of the vitrification substrate and thus induce radionuclide leaching. Removal of ⁹⁰Sr can reduce the heat generation and shorten the cooling time of the vitrification substrate in the repository, which is favorable for further deep geological disposal of the radioactive waste.

In this study, the researchers prepared an organic-inorganic hybrid adsorbent named as HEMAP/SiO₂-P. This novel adsorbent uses SiO₂-P as a stabilizing framework, with 2-hydroxyethyl-2-methyl-2-propenoate phosphate (HEMAP) encapsulated inside using a vacuum impregnation technique. The primary objective was to investigate the adsorption behavior of this adsorbent on the stable strontium nuclide in a 3 M HNO₃ medium.

Experimental results showed that the prepared adsorbent exhibited good stability against acidic conditions and displayed remarkable adsorption capabilities toward stable strontium nuclide. Mechanistic analysis further revealed that each strontium molecule formed coordination bonds with two HEMAP molecules during the adsorption process.

In addition, two nitrate ions (NO₃-) were required to maintain the charge balance.

This study not only developed a novel method for the preparation of a highly stable silica-based adsorbent, but also provided relevant experimental data and theoretical basis for the selective separation of strontium in acidic environments.

This work was supported by the National Natural Science Foundation of China.

Schematic illustration of HEMAP/SiO₂-P preparation process. (Image by ZHANG Shichang) 

Adsorption performance of 12 metal ions by HEMAP/SiO₂-P. (Image by ZHANG Shichang)