Radiation-induced surface modification of silanized silica with n-alkyl-imidazolium ionic liquids and their applications for the removal of ReO4- as an analogue for TcO4-

As a radioactive fission product, Tc-99 always existed in the combined extreme conditions of super acidity, high ionic strength, and strong radiation field, which made the efficient removal of Tc a challenge. Herein, for the first time, a series of n-alkyl-imidazolium ionic liquids were grafted onto silanized silica using radiation technique. The surface and structure properties of prepared adsorbents (SiO2-MPTS-[C(n)VIm]Br) were characterized by FT-IR, TGA, XPS, BET, and SEM-EDS. Subsequently, their adsorption properties for ReO4- (a nonradioactive surrogate of TcO4-) were studied in detail. These adsorbents exhibited an adsorption capacity of approximately 190 mg g(-1) for ReO4-. It was found that adsorbents with longer alkyl chains showed better selectivity against ReO4- under the conditions of strong acids and a large excess of competitive ions. Column experiments indicated that these adsorbents could be recycled 10 times with negligible capacity loss. In addition, their adsorption performance remained unchanged after 800 kGy radiation. The column experiments of treating simulated radioactive wastewater proved that SiO2-MPTS-[C(n)VIm]Br was promising for selective separation of TcO4-/ReO4- from a variety of fission products. Lastly, XPS and FT-IR analysis confirmed that the adsorption mechanism was based on ion-exchange.

Automated summary

In this study, a series of n-alkyl-imidazolium ionic liquids were grafted onto silanized silica using radiation technique for efficient removal of Tc. The prepared adsorbents exhibited good adsorption properties for ReO4- and could be recycled multiple times with negligible capacity loss. XPS and FT-IR analysis confirmed that the adsorption mechanism was based on ion-exchange, indicating potential for selective separation of TcO4-/ReO4- from radioactive wastewater.