Influence of weathering of bottom ash on the leaching behavior of cesium

Abstract

Phase transformation and leaching of cesium from incineration bottom ash were investigated by conducting accelerating weathering experiment. Four kinds of weathering condition were set; namely, blank (under nitrogen gas condition), wetting and drying, freezing and thawing, and exposure to carbon dioxide gas. Leaching of cesium under blank condition didn't change. On the other hand, drastic decrease of leaching of cesium was identified under carbon dioxide exposure. From XRD analysis, formation of calcite was identified. It deemed that newly formed calcite inhibited the leaching of Cs by covering reactive surface of bottom ash. In both wetting-drying and freezing-thawing condition, leaching of Cs increased initially. But it decreased after several weeks then it became lower than blank finally. This decrease of leaching also seems to be caused by formation of calcite.