A novel method to convert Cs-polluted soil into pollucite-base glass-ceramics for Cs immobilization

Abstract

The Fukushima nuclear accident produced huge amounts of 137Cs -polluted (radioactive cesium) soil which must be dealt with to prevent the spreading of radioactive Cs into the environment. In this work, a novel and facile process was developed to directly convert Cs-polluted soil (metakaolin) into pollucite-based glass-ceramics in which Cs, as a simulant of nuclide, is immobilized. Pollucite-based glass-ceramics was synthesized by sintering mixture of a specially formulated glass powder and a Cs-precursor powder which was prepared via a simple chemistry route (simulating the Cs contaminated soil). Thermal evolution, phase composition, microstructure evolution, thermal expansion behaviors, and chemical stability of the pollucite-based glass-ceramics were characterized. X-ray diffraction confirmed that crystalline pollucite was precipitated in the amorphous glass at 1050 °C. Structural and morphological characterizations revealed that Cs was immobilized in the crystalline structure of pollucite, as well as in the glass surrounding pollucite grains. Extensive tests demonstrated that the Cs leaching rate was fairly low (4.1 × 10−3 g/m2/d), and pollucite-based glass-ceramics had the excellent chemical stability. We believe that this study offers a potential technique for immobilization of Cs-polluted soil and radionuclide.