The development of selective adsorbents has become very important for the effective multi-nuclide decontamination. In this study, the selective adsorption properties of 26 nuclides for different types of zeolites (A, L, natural mordenite (NM), Ag-NM) were examined in the presence of boric acid.
The batch adsorption experiments were carried out using four kinds of test solutions containing boric acid and calcium hydroxide; (1)DW (distilled water) + H3BO4: 3,000 ppm + LiOH: 10 ppb, (2)DW + Ca(OH)2: 500 ppm + H3BO4: 3,000 ppm + LiOH: 10 ppb, (3)Seawater (30% diluted) + H3BO4: 3,000 ppm, (4)Seawater + H3BO4: 3,000ppm. The uptake (%) of Sr2+ for zeolite A (A-51J), Cs+ for natural mordenite (NM, 2460#, Ayashi, Sendai), and I− for Ag-NM was determined under the following conditions; Concentration of Sr2+, Cs+ and I− ions: 10 ppm, V/m = 100 cm3/g, 25°C, 24 h. The uptake (%) of Sr2+, Cs+ and I− ions was estimated to be above 90%, while tended to decrease in the presence of seawater. Especially, the uptake (%) of I− ions for Ag-NM markedly decreased in the presence of seawater.
As for the zeolites A and L, the uptake (%) of 26 elements was determined by using two kinds of test solutions; (1)DW (distilled water) + H3BO4: 3,000 ppm + LiOH: 10 ppb + 26 nuclides: 10 ppm, (2)Seawater (30% diluted) + H3BO4: 3,000 ppm + 26 nuclides: 10 ppm.
Zeolite A has relatively large uptake percentage for Sr, Co, Ni and Zn, and zeolite L has high adsorbability to lanthanoid group of Eu, Ce and Pr. The increase in pH led to the enhancement of uptake (%), while the hydrolysis of metal ions should be also considered. The multi-nuclides separation is thus expected by considering the difference in uptake properties of zeolite A, L and natural mordenite.
