In this paper, the performance of adsorbing and retarding 125I (substituted for 129I) for mixed minerals as buffer, backfill material was investigated. The distribution coefficient Kds by batch sorption experiments were determined for four kinds of minerals and one kind of bentonite under atmosphere. Sorption and desorption of radioiodine on several minerals were studied under low oxygen ambience at first time in the domestic, and apparent diffusion coefficient Da of 125I- was determined for mixed minerals under atmosphere. The results as follows: Distribution coefficient Kds of 125I- under atmosphere: bentonite is 3.23 ml(center-dot)g-1, chalcopyrite is 72.42 ml(center-dot)g-1, galena is 118.9 ml(center-dot)g-1, pyrite is 1.93 ml(center-dot)g-1, cinnabar is 55.48 ml(center-dot)g-1, and the corresponding Kds under low oxygen ambience: galena is 88.48 ml(center-dot)g-1, chalcopyrite is 6.47 ml(center-dot)g-1. when pH of solution was in the range of 2.25-12.26, Kds of 125I- on chalcopyrite, galena, pyrite and cinnabar decreased with increase of pH under atmosphere. Kds of 125I- on several minerals increased with increase of mineral ratio in mixed materials under atmosphere. Under the same condition, Kds of 125I- on chalcopyrite and galena were larger than Kds of 125IO3 -. Sorption of 125I- on galena seems to be irreversible. Apparent diffusion coefficient Da of 125I- in the mixed material was measured by the flow-through diffusion way, Da values under atmosphere was given: Da=7.29 x 10-12 m2(center-dot)s-1.
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