Effect of pH and Chemical Composition of Solution on Sorption and Retention of Cesium by Feldspar, Illite, and Zeolite as Cesium Sorbent From Landfill Leachate

Abstract

This study investigated cesium (Cs) sorption and retention by 4 types of minerals, which were considered as candidate sorbents to prevent radiocesium leaching from landfill sites containing radiocesium wastes. Feldspar, 2 types of illite, and natural zeolite were examined for sorption of stable Cs under deionized water or landfill leachate conditions. In the pH range of 6 to 11, feldspar had a large effect on Cs sorption, but the other minerals did not. The sorption isotherms were obtained using 2 types of Cs solutions, which were fit to the Freundlich model. The difference of Freundlich exponent between the 2 types of Cs solutions was attributed to the sorption mechanisms of the minerals. These minerals had two or more types of sorption sites for cations; however, one specific type of site had a potentially higher selectivity for Cs in the leachate. Additionally, extraction test results showed that retention capacity for Cs in the leachate decreased in the following order: natural zeolite > illite Y > illite W > feldspar. Although illite W and illite Y were identified as the same mineral by XRD analysis, they had different retention capacities described as radiocesium interception potential, which is an index of the number of specific sites for Cs.