Transformation of Cs-LTA type of zeolite to pollucite phase using hot pressing method

Abstract

Cesium aluminosilicate phases are of the great interest as possible hosts for Cs immobilization in radioactive waste management. Cs-exchanged form of Na, Ca-LTA type of zeolite (Cs-LTA) was prepared by standard procedure of ion exchange. In order to obtain pollucite this Cs-LTA zeolite was pressurless sintered and hot pressed at certain temperatures. XRD analyses were used to study structural changes of Cs-LTA before and after thermal treatments. Pressurless sintered sample recrystallized into pollucite phase after heat treatment at 1000 °C (3 h) (PLS1000) and hot pressed sample at 750 °C (3 h) using pressure of 35 MPa (HP750), indicating reduced temperature of 250 degrees. HP750 has higher density than PLS1000 which leads to higher value of compressive strength. The HP750 showed better resistance to Cs leaching than the PLS1000. Obtained results of HP750 sample indicate that these ceramic forms, based on pollucite phase, are promising for the permanent immobilization of Cs radionuclides.