Investigations on the ion exchange process of Cs+ and Sr2+ cations by ETS materials

Ion exchange experiments were carried out for evaluation the removal capability of cesium and strontium ions by the microporous Engelhard Titanium Silicates – 4 and 10 (ETS-4 and ETS-10, respectively) synthesized from alkaline gels. Ionic selectivities were estimated from the ion exchange isotherms, Kielland and Langmuir plots. It is shown that both microporous titanosilicates perform under a similar ion exchange profile against Cs+ cations and the selectivity of ETS-4 for Sr2+ is highly depended on temperature. ETS-10 is unselective for Sr2+ over a wide range of equivalent ionic fraction of strontium in solution. The Langmuir isotherms indicate that in the absence of ionic competition both titanosilicates retain Cs+ and Sr2+ cations, as much as their ion exchange capacities. These positive results promote ETS materials as very good candidates for the removal of both cesium and strontium from nuclear waste solutions.