Contrasting immobilization behavior of Cs+ and Sr2+cations in a titanosilicate matrix

Abstract

ETS-10 titanosilicate was tested as an adsorbent for the removal of Cs⁺ and Sr²⁺ cations from radioactive waters, considering both the ion exchange and the behaviour of the loaded adsorbent during thermal conditioning. The studies indicate that ETS-10 has a high and similar affinity for both Cs⁺ and Sr²⁺ cations reaching the ion exchange capacity of ETS-10 at a concentration of about 50 milliequivalents gram per liter. Thermal treatment of Cs⁺- and Sr²⁺-exchanged ETS-10 materials results in melting at approximately 700 °C. The melting temperature increases with the initial Cs⁺ and Sr²⁺ concentration and is higher for Sr²⁺ than for Cs⁺ exchanged ETS-10. Recrystallisation occurs only in the presence of Sr²⁺ as evidenced by the exothermic effects between 800 and 900 °C. After calcination of Cs⁺- and Sr²⁺-exchanged ETS-10 in air at 800 °C, two types of materials were obtained: an amorphous glass material with homogeneous Cs⁺ distribution and a strontium fresnoites glass–ceramic material.