Novel silica-based adsorbent helps selective separation of strontium

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 silica-based adsorbent for the highly selective separation of strontium (Sr) from an acidic medium.

The results were published in the Journal of Hazardous Materials.

Radioactive strontium, known as ⁹⁰Sr, is of concern because it's highly toxic both radiologically and biochemically. When high-level liquid waste (HLLW) is processed through vitrification, the heat released from the decay of ⁹⁰Sr can cause problems. This heat can destabilize the material in which it's contained, potentially leading to the release of other radioactive substances. However, ⁹⁰Sr can also be reused as a special radioactive or heat source, which can help reduce the amount of waste to be disposed of with lower overall costs.

To address the above issues, the research team developed a novel porous adsorbent called CEPA@SBA-15-APTES. This adsorbent is made by modifying mesoporous silica to selectively separate Sr. They studied how this adsorbent behaves when exposed to different environments using Sr-stable nuclides.

They found that the adsorption reached equilibrium in 30 minutes in a solution with a low concentration of nitric acid (HNO₃) and in only five minutes in a solution with a higher concentration of HNO₃.

Importantly, the adsorbent showed excellent selectivity for Sr in 3 M HNO₃ simulated HLLW solution. The mechanism of Sr adsorption differs depending on the acidity of the solution: Ion exchange occurs in solutions with low HNO₃ concentration, while coordination occurs in solutions with higher HNO₃ concentration.

This study develops a novel material for the efficient separation of strontium, which is a reference for the selective separation and recovery of radionuclides.