Pages: 60-65

Authors: Slavko D. Dimović, Ivana V. Jelić, and Marija Z. Šljivić-Ivanović

Abstract

The probability of Cs⁺ and Co²⁺ ions retention by immobilization processes in the cement matrix was determinate as the subject of analyses: matrix design, water/cement ratio, and structure porosity. Comparison of experimental results was accomplished by Hespe standard leaching method. Diffusion and semi-empirical models were used for the assessment of the washing rate as a function of time. The higher value of cement matrix mechanical resistance corresponds to a lower value of Co²⁺ and Cs⁺ ions leaching. The Co²⁺ leaching level was more than two orders of magnitude less than the leaching level of Cs⁺. The influence of bentonite and zeolite on Co²⁺ leaching reduction was significantly smaller in comparison with Cs⁺, while zeolite had a higher Cs⁺ and Co²⁺ sorption ability than bentonite. Under static leaching conditions, the contribution of diffusion to the total transport of ions in the matrix porous medium was dominant. The contribution of matrix dissolution was insignificant concerning the dominant contribution of diffusion and surface washing. The semi-empirical model showed a better approximation of the Co²⁺ and Cs⁺ ions laboratory leaching process.

Key words: leaching, immobilization, sorption, radioactive waste

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