Retardation capacity of organophilic bentonite for anionic fission products |
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Authors: | Riebe B Bors J Dultz S |
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Affiliation: | 1. School of Chemical Sciences, University of Chinese Academy of Sciences, 19 Yuquan Road, Shijingshan District, Beijing 100049, PR China;2. Institute of Chemistry, Chinese Academy of Sciences (CAS), 2 Zhongguancun North Road, Haidian District, Beijing 100190, PR China |
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Abstract: | Sorption and diffusivity of iodide and pertechnetate (I- and TcO4-) on MX-80 bentonite with different hexadecylpyridinium (HDPy+) loadings were studied using equilibrium solutions of different ionic strengths. In HDPy(+)-modified bentonite, iodide and pertechnetate ions exhibited increasing sorption (characterized by the distribution ratio, Rd), while Cs+ and Sr2+ showed decreasing sorption with increasing organophilicity. In case of medium-loading levels, the simultaneous sorption of anions (I- and TcO4-) and cations (Cs+ and Sr2+) was observed. Sorption of ions was influenced by the composition of the electrolytes employed. It decreased gradually with increasing ionic strength of the electrolyte solutions. The experiments revealed the general tendency that the diffusivity (Da [cm2.s-1]) for iodide and pertechnetate decreases with increasing organophilicity and increases with increasing ionic strength of the equilibrium solutions, confirming the results of the sorption experiments. Additionally, some mineralogical and chemical investigations, like IR spectral analysis of the organo-bentonite samples and exchange behavior of HDPy+, were performed. On the basis of these analyses, it was concluded that the alkylammonium ions are sorbed as (1) HDPy+ cations, (2) HDPyCl molecules and (3) micelles with decreasing binding intensities in this order. |
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Keywords: | Organo-clays Radioactive waste Anion-sorption Technetium Iodine Diffusion |
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