Creation of Smart Polydimethylsiloxane Sponge for Selective Recovery of Lanthanides from Radioactive Wastes

Mutual separation of lanthanides and minor actinides from high-level liquid wastes can effectively improve the efficiency of partitioning and transmutation strategy, reducing the potential risks of high-level liquid wastes to the environment. Conventional separation techniques have been shown efficiency in lanthanides separation but are limited by their long operation time and potential hazards to environment. In our research, a low-cost adsorbent was developed by impregnating lipophilic extractant bis(2-ethylhexyl) phosphate (HDEHP) in the polydimethylsiloxane (PDMS) sponge via hydrophobic interaction, aimed to selectively and efficiently remove lanthanides from high-level liquid wastes. The obtained PDMS-HDEHP sponge can rapidly adsorb lanthanide ions and showed the best lanthanide adsorption performance in the pH3 nitric acid solution. Via non-linear fitting the experimental results by Langmuir adsorption isotherm model, we found that the maximum lanthanide adsorption capacity of PDMS-HDEHP can reach 8.06–21.51 mg/g depending on the ionic radii and charges, higher than many adsorbents. Furthermore, nearly all of adsorbed lighter lanthanide ions can be recovered into the solution after ethylenediaminetetraacetic acid (EDTA) treatment. It is noteworthy that synthesized PDMS-HDEHP sponge can still maintain lanthanide adsorption ability after desorption, indicating that the obtained sponge owns tremendous potential in nuclear waste management due to its high adsorption capacities and regeneration abilities.