Preparation and Characterization of Zeolite-Containing Composite Sheets for Decontamination of Radioactive Ions Dissolved in Water (III)

Abstract

Zeolite-containing composite sheets are useful as filters to decontamination of radioactive ionscontaining water, compared with zeolite powders. Based on various preliminary results, we prepared zeolitecontaining composite sheets from zeolite powders with different particle sizes, binder polymer with different binder/zeolite weight ratios, and three nonwoven fabrics. The binder/zeolite mat was sandwiched between the two nonwoven fabrics by thermal pressing. The water filtration performance and the amount of detached zeolite particles during filtration, and the adsorption performance of strontium ions in water were studied in terms of the binder/zeolite weight ratio, the particle sizes of zeolite, and others. The water filtration performance was the highest when the nonwoven fabric with the lowest basis weight was used in the composite making at the binder/zeolite weight ratios ranging from 25 to 70 %. The amount of detached zeolite particles during filtration was, however, the highest when the nonwoven fabric with the lowest basis weight was used. The composite sheets containing zeolite powder with the largest particle size had the highest filtration performance (or shortest filtration time) and the lowest amount of detached zeolite particles during the initial filtration. The adsorption performance of strontium ions in simulated seawater for the zeolitecontaining composite sheets were almost similar to those of zeolite powders alone under equilibrium conditions. Thus, the Sr²⁺ adsorption performance of zeolite powder was almost maintained for the zeolitecontaining composite sheets at the same zeolite content. As a result, the balance between the Sr²⁺ adsorption and filtration performances should be taken into account in designing the zeolite-containing sheets for practical use.