Adsorption Of Eu(Ⅲ), Th(Ⅳ) And Se(Ⅳ) On Beishan Granite

Beishan in Gansu province is the preliminarily selected site for the repository of high-level radioactive waste in China.It is of practical significance to investigate the similarities and differences between the adsorption of the most concerned radionuclides on granite from different boreholes and to explore the reasons for the differences which may help us to objectively understand the preselected sites,and may contribute data support to the safety assesment. This work has important practical significance.Based on detailed characterization of Beishan granite from boreholes No.4 and No.10, adsorption of Eu(III), Th(IV) and Se(IV) on the granite were studied as a function of pH value, ionic strength(I), humic acid and fulvic acid. The reasons for high adsorption distribution coefficieat of Se(IV) adsorption on BS04 were discussed.The results showed that pH was the key factors for Eu(III), Th(IV) and Se(IV) adsorption on Beishan granite.Ionic strength had no effect on the adsorption of Th(IV) and Se(IV),but had significant effect on Eu(III) adsorption in low pH range. FA and HA had few effects on Se(IV) adsorption but enhanced the adsorption of Th(IV) in low pH range. FA and HA enhanced the adsorption of Eu(III) in low pH range, but suppressed the adsorption in high pH range. Comparing with Se(IV), the adsorption of Se(VI) on Beishan granite was relatively weak, with distribution coefficients less than 1 mL/g in all experimental conditions. The adsorption distribution coeffieats of Se(IV) adsorption on BS 04 granite were nearly two orders of magnitude higher than those on BS 10 and BS 03 granite,which was related to higher iron content of BS 04 granite.